diff --git a/build.zig b/build.zig
index a7f42383e..1ac50bbf4 100644
--- a/build.zig
+++ b/build.zig
@@ -3,6 +3,7 @@ const builtin = @import("builtin");
 const fs = std.fs;
 const Builder = std.build.Builder;
 const LibExeObjStep = std.build.LibExeObjStep;
+const apprt = @import("src/apprt.zig");
 const glfw = @import("vendor/mach/libs/glfw/build.zig");
 const fontconfig = @import("pkg/fontconfig/build.zig");
 const freetype = @import("pkg/freetype/build.zig");
@@ -45,6 +46,7 @@ comptime {
 var tracy: bool = false;
 var enable_coretext: bool = false;
 var enable_fontconfig: bool = false;
+var app_runtime: apprt.Runtime = .none;
 
 pub fn build(b: *std.build.Builder) !void {
     const optimize = b.standardOptimizeOption(.{});
@@ -77,6 +79,12 @@ pub fn build(b: *std.build.Builder) !void {
         "Enable fontconfig for font discovery (default true on Linux)",
     ) orelse target.isLinux();
 
+    app_runtime = b.option(
+        apprt.Runtime,
+        "app-runtime",
+        "The app runtime to use. Not all values supported on all platforms.",
+    ) orelse apprt.Runtime.default(target);
+
     const static = b.option(
         bool,
         "static",
@@ -111,6 +119,7 @@ pub fn build(b: *std.build.Builder) !void {
     exe_options.addOption(bool, "tracy_enabled", tracy);
     exe_options.addOption(bool, "coretext", enable_coretext);
     exe_options.addOption(bool, "fontconfig", enable_fontconfig);
+    exe_options.addOption(apprt.Runtime, "app_runtime", app_runtime);
 
     // Exe
     {
@@ -120,7 +129,7 @@ pub fn build(b: *std.build.Builder) !void {
         }
 
         exe.addOptions("build_options", exe_options);
-        exe.install();
+        if (app_runtime != .none) exe.install();
 
         // Add the shared dependencies
         _ = try addDeps(b, exe, static);
@@ -134,7 +143,7 @@ pub fn build(b: *std.build.Builder) !void {
         b.installFile("dist/macos/Ghostty.icns", "Ghostty.app/Contents/Resources/Ghostty.icns");
     }
 
-    // On Mac we can build the app.
+    // On Mac we can build the embedding library.
     if (builtin.target.isDarwin()) {
         const static_lib_aarch64 = lib: {
             const lib = b.addStaticLibrary(.{
@@ -539,22 +548,38 @@ fn addDeps(
     }
 
     if (!lib) {
-        step.addModule("glfw", glfw.module(b));
-
         // We always statically compile glad
         step.addIncludePath("vendor/glad/include/");
         step.addCSourceFile("vendor/glad/src/gl.c", &.{});
 
-        // Glfw
-        const glfw_opts: glfw.Options = .{
-            .metal = step.target.isDarwin(),
-            .opengl = false,
-        };
-        try glfw.link(b, step, glfw_opts);
+        switch (app_runtime) {
+            .none => {},
 
-        // Imgui
-        const imgui_step = try imgui.link(b, step, imgui_opts);
-        try glfw.link(b, imgui_step, glfw_opts);
+            .glfw => {
+                step.addModule("glfw", glfw.module(b));
+                const glfw_opts: glfw.Options = .{
+                    .metal = step.target.isDarwin(),
+                    .opengl = false,
+                };
+                try glfw.link(b, step, glfw_opts);
+
+                // Must also link to imgui
+                const imgui_step = try imgui.link(b, step, imgui_opts);
+                try glfw.link(b, imgui_step, glfw_opts);
+            },
+
+            .gtk => {
+                // We need glfw for GTK because we use GLFW to get DPI.
+                step.addModule("glfw", glfw.module(b));
+                const glfw_opts: glfw.Options = .{
+                    .metal = step.target.isDarwin(),
+                    .opengl = false,
+                };
+                try glfw.link(b, step, glfw_opts);
+
+                step.linkSystemLibrary("gtk4");
+            },
+        }
     }
 
     return static_libs;
diff --git a/include/ghostty.h b/include/ghostty.h
index 1764ef445..6da1db805 100644
--- a/include/ghostty.h
+++ b/include/ghostty.h
@@ -51,7 +51,8 @@ typedef enum {
 } ghostty_input_mouse_state_e;
 
 typedef enum {
-    GHOSTTY_MOUSE_LEFT = 1,
+    GHOSTTY_MOUSE_UNKNOWN,
+    GHOSTTY_MOUSE_LEFT,
     GHOSTTY_MOUSE_RIGHT,
     GHOSTTY_MOUSE_MIDDLE,
 } ghostty_input_mouse_button_e;
diff --git a/nix/devshell.nix b/nix/devshell.nix
index 343546312..e343682bd 100644
--- a/nix/devshell.nix
+++ b/nix/devshell.nix
@@ -22,6 +22,8 @@
 , expat
 , fontconfig
 , freetype
+, glib
+, gtk4
 , harfbuzz
 , libpng
 , libGL
@@ -53,6 +55,9 @@ let
     libXcursor
     libXi
     libXrandr
+
+    gtk4
+    glib
   ];
 in mkShell rec {
   name = "ghostty";
@@ -102,6 +107,10 @@ in mkShell rec {
     libXi
     libXinerama
     libXrandr
+
+    # Only needed for GTK builds
+    gtk4
+    glib
   ];
 
   # This should be set onto the rpath of the ghostty binary if you want
diff --git a/src/App.zig b/src/App.zig
index 4efbda3b2..683a70f47 100644
--- a/src/App.zig
+++ b/src/App.zig
@@ -9,7 +9,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const build_config = @import("build_config.zig");
 const apprt = @import("apprt.zig");
-const Window = @import("Window.zig");
+const Surface = @import("Surface.zig");
 const tracy = @import("tracy");
 const input = @import("input.zig");
 const Config = @import("config.zig").Config;
@@ -22,63 +22,31 @@ const DevMode = @import("DevMode.zig");
 
 const log = std.log.scoped(.app);
 
-const WindowList = std.ArrayListUnmanaged(*Window);
-
-/// The type used for sending messages to the app thread.
-pub const Mailbox = BlockingQueue(Message, 64);
+const SurfaceList = std.ArrayListUnmanaged(*apprt.Surface);
 
 /// General purpose allocator
 alloc: Allocator,
 
-/// The runtime for this app.
-runtime: apprt.runtime.App,
-
-/// The list of windows that are currently open
-windows: WindowList,
+/// The list of surfaces that are currently active.
+surfaces: SurfaceList,
 
 // The configuration for the app.
 config: *const Config,
 
 /// The mailbox that can be used to send this thread messages. Note
 /// this is a blocking queue so if it is full you will get errors (or block).
-mailbox: *Mailbox,
+mailbox: Mailbox.Queue,
 
 /// Set to true once we're quitting. This never goes false again.
 quit: bool,
 
-/// Mac settings
-darwin: if (Darwin.enabled) Darwin else void,
-
-/// Mac-specific settings. This is only enabled when the target is
-/// Mac and the artifact is a standalone exe. We don't target libs because
-/// the embedded API doesn't do windowing.
-pub const Darwin = struct {
-    pub const enabled = builtin.target.isDarwin() and build_config.artifact == .exe;
-
-    tabbing_id: *macos.foundation.String,
-
-    pub fn deinit(self: *Darwin) void {
-        self.tabbing_id.release();
-        self.* = undefined;
-    }
-};
-
 /// Initialize the main app instance. This creates the main window, sets
 /// up the renderer state, compiles the shaders, etc. This is the primary
 /// "startup" logic.
 pub fn create(
     alloc: Allocator,
-    rt_opts: apprt.runtime.App.Options,
     config: *const Config,
 ) !*App {
-    // Initialize app runtime
-    var app_backend = try apprt.runtime.App.init(rt_opts);
-    errdefer app_backend.terminate();
-
-    // The mailbox for messaging this thread
-    var mailbox = try Mailbox.create(alloc);
-    errdefer mailbox.destroy(alloc);
-
     // If we have DevMode on, store the config so we can show it
     if (DevMode.enabled) DevMode.instance.config = config;
 
@@ -86,78 +54,36 @@ pub fn create(
     errdefer alloc.destroy(app);
     app.* = .{
         .alloc = alloc,
-        .runtime = app_backend,
-        .windows = .{},
+        .surfaces = .{},
         .config = config,
-        .mailbox = mailbox,
+        .mailbox = .{},
         .quit = false,
-        .darwin = if (Darwin.enabled) undefined else {},
     };
-    errdefer app.windows.deinit(alloc);
-
-    // On Mac, we enable window tabbing. We only do this if we're building
-    // a standalone exe. In embedded mode the host app handles this for us.
-    if (Darwin.enabled) {
-        const NSWindow = objc.Class.getClass("NSWindow").?;
-        NSWindow.msgSend(void, objc.sel("setAllowsAutomaticWindowTabbing:"), .{true});
-
-        // Our tabbing ID allows all of our windows to group together
-        const tabbing_id = try macos.foundation.String.createWithBytes(
-            "dev.ghostty.window",
-            .utf8,
-            false,
-        );
-        errdefer tabbing_id.release();
-
-        // Setup our Mac settings
-        app.darwin = .{
-            .tabbing_id = tabbing_id,
-        };
-    }
-    errdefer if (comptime builtin.target.isDarwin()) app.darwin.deinit();
+    errdefer app.surfaces.deinit(alloc);
 
     return app;
 }
 
 pub fn destroy(self: *App) void {
-    // Clean up all our windows
-    for (self.windows.items) |window| window.destroy();
-    self.windows.deinit(self.alloc);
-    if (Darwin.enabled) self.darwin.deinit();
-    self.mailbox.destroy(self.alloc);
+    // Clean up all our surfaces
+    for (self.surfaces.items) |surface| surface.deinit();
+    self.surfaces.deinit(self.alloc);
+
     self.alloc.destroy(self);
-
-    // Close our windowing runtime
-    self.runtime.terminate();
-}
-
-/// Wake up the app event loop. This should be called after any messages
-/// are sent to the mailbox.
-pub fn wakeup(self: App) void {
-    self.runtime.wakeup() catch return;
-}
-
-/// Run the main event loop for the application. This blocks until the
-/// application quits or every window is closed.
-pub fn run(self: *App) !void {
-    while (!self.quit and self.windows.items.len > 0) {
-        try self.tick();
-    }
 }
 
 /// Tick ticks the app loop. This will drain our mailbox and process those
-/// events.
-pub fn tick(self: *App) !void {
-    // Block for any events.
-    try self.runtime.wait();
-
-    // If any windows are closing, destroy them
+/// events. This should be called by the application runtime on every loop
+/// tick.
+///
+/// This returns whether the app should quit or not.
+pub fn tick(self: *App, rt_app: *apprt.App) !bool {
+    // If any surfaces are closing, destroy them
     var i: usize = 0;
-    while (i < self.windows.items.len) {
-        const window = self.windows.items[i];
-        if (window.shouldClose()) {
-            window.destroy();
-            _ = self.windows.swapRemove(i);
+    while (i < self.surfaces.items.len) {
+        const surface = self.surfaces.items[i];
+        if (surface.shouldClose()) {
+            rt_app.closeSurface(surface);
             continue;
         }
 
@@ -165,34 +91,27 @@ pub fn tick(self: *App) !void {
     }
 
     // Drain our mailbox only if we're not quitting.
-    if (!self.quit) try self.drainMailbox();
+    if (!self.quit) try self.drainMailbox(rt_app);
+
+    // We quit if our quit flag is on or if we have closed all surfaces.
+    return self.quit or self.surfaces.items.len == 0;
 }
 
-/// Create a new window. This can be called only on the main thread. This
-/// can be called prior to ever running the app loop.
-pub fn newWindow(self: *App, msg: Message.NewWindow) !*Window {
-    var window = try Window.create(self.alloc, self, self.config, msg.runtime);
-    errdefer window.destroy();
-
-    try self.windows.append(self.alloc, window);
-    errdefer _ = self.windows.pop();
-
-    // Set initial font size if given
-    if (msg.font_size) |size| window.setFontSize(size);
-
-    return window;
+/// Add an initialized surface. This is really only for the runtime
+/// implementations to call and should NOT be called by general app users.
+/// The surface must be from the pool.
+pub fn addSurface(self: *App, rt_surface: *apprt.Surface) !void {
+    try self.surfaces.append(self.alloc, rt_surface);
 }
 
-/// Close a window and free all resources associated with it. This can
-/// only be called from the main thread.
-pub fn closeWindow(self: *App, window: *Window) void {
+/// Delete the surface from the known surface list. This will NOT call the
+/// destructor or free the memory.
+pub fn deleteSurface(self: *App, rt_surface: *apprt.Surface) void {
     var i: usize = 0;
-    while (i < self.windows.items.len) {
-        const current = self.windows.items[i];
-        if (window == current) {
-            window.destroy();
-            _ = self.windows.swapRemove(i);
-            return;
+    while (i < self.surfaces.items.len) {
+        if (self.surfaces.items[i] == rt_surface) {
+            _ = self.surfaces.swapRemove(i);
+            continue;
         }
 
         i += 1;
@@ -200,29 +119,51 @@ pub fn closeWindow(self: *App, window: *Window) void {
 }
 
 /// Drain the mailbox.
-fn drainMailbox(self: *App) !void {
+fn drainMailbox(self: *App, rt_app: *apprt.App) !void {
     while (self.mailbox.pop()) |message| {
         log.debug("mailbox message={s}", .{@tagName(message)});
         switch (message) {
-            .new_window => |msg| _ = try self.newWindow(msg),
-            .new_tab => |msg| try self.newTab(msg),
+            .new_window => |msg| try self.newWindow(rt_app, msg),
+            .new_tab => |msg| try self.newTab(rt_app, msg),
+            .close => |surface| try self.closeSurface(rt_app, surface),
             .quit => try self.setQuit(),
-            .window_message => |msg| try self.windowMessage(msg.window, msg.message),
+            .surface_message => |msg| try self.surfaceMessage(msg.surface, msg.message),
+            .redraw_surface => |surface| try self.redrawSurface(rt_app, surface),
         }
     }
 }
 
-/// Create a new tab in the parent window
-fn newTab(self: *App, msg: Message.NewWindow) !void {
-    if (comptime !builtin.target.isDarwin()) {
-        log.warn("tabbing is not supported on this platform", .{});
+fn closeSurface(self: *App, rt_app: *apprt.App, surface: *Surface) !void {
+    if (!self.hasSurface(surface)) return;
+    rt_app.closeSurface(surface.rt_surface);
+}
+
+fn redrawSurface(self: *App, rt_app: *apprt.App, surface: *apprt.Surface) !void {
+    if (!self.hasSurface(&surface.core_surface)) return;
+    rt_app.redrawSurface(surface);
+}
+
+/// Create a new window
+fn newWindow(self: *App, rt_app: *apprt.App, msg: Message.NewWindow) !void {
+    if (!@hasDecl(apprt.App, "newWindow")) {
+        log.warn("newWindow is not supported by this runtime", .{});
         return;
     }
 
-    // In embedded mode, it is up to the embedder to implement tabbing
-    // on their own.
-    if (comptime build_config.artifact != .exe) {
-        log.warn("tabbing is not supported in embedded mode", .{});
+    const parent = if (msg.parent) |parent| parent: {
+        break :parent if (self.hasSurface(parent))
+            parent
+        else
+            null;
+    } else null;
+
+    try rt_app.newWindow(parent);
+}
+
+/// Create a new tab in the parent window
+fn newTab(self: *App, rt_app: *apprt.App, msg: Message.NewTab) !void {
+    if (!@hasDecl(apprt.App, "newTab")) {
+        log.warn("newTab is not supported by this runtime", .{});
         return;
     }
 
@@ -232,16 +173,12 @@ fn newTab(self: *App, msg: Message.NewWindow) !void {
     };
 
     // If the parent was closed prior to us handling the message, we do nothing.
-    if (!self.hasWindow(parent)) {
+    if (!self.hasSurface(parent)) {
         log.warn("new_tab parent is gone, not launching a new tab", .{});
         return;
     }
 
-    // Create the new window
-    const window = try self.newWindow(msg);
-
-    // Add the window to our parent tab group
-    parent.addWindow(window);
+    try rt_app.newTab(parent);
 }
 
 /// Start quitting
@@ -249,28 +186,28 @@ fn setQuit(self: *App) !void {
     if (self.quit) return;
     self.quit = true;
 
-    // Mark that all our windows should close
-    for (self.windows.items) |window| {
-        window.window.setShouldClose();
+    // Mark that all our surfaces should close
+    for (self.surfaces.items) |surface| {
+        surface.setShouldClose();
     }
 }
 
 /// Handle a window message
-fn windowMessage(self: *App, win: *Window, msg: Window.Message) !void {
+fn surfaceMessage(self: *App, surface: *Surface, msg: apprt.surface.Message) !void {
     // We want to ensure our window is still active. Window messages
     // are quite rare and we normally don't have many windows so we do
     // a simple linear search here.
-    if (self.hasWindow(win)) {
-        try win.handleMessage(msg);
+    if (self.hasSurface(surface)) {
+        try surface.handleMessage(msg);
     }
 
     // Window was not found, it probably quit before we handled the message.
     // Not a problem.
 }
 
-fn hasWindow(self: *App, win: *Window) bool {
-    for (self.windows.items) |window| {
-        if (window == win) return true;
+fn hasSurface(self: *App, surface: *Surface) bool {
+    for (self.surfaces.items) |v| {
+        if (&v.core_surface == surface) return true;
     }
 
     return false;
@@ -284,28 +221,55 @@ pub const Message = union(enum) {
     /// Create a new tab within the tab group of the focused window.
     /// This does nothing if we're on a platform or using a window
     /// environment that doesn't support tabs.
-    new_tab: NewWindow,
+    new_tab: NewTab,
+
+    /// Close a surface. This notifies the runtime that a surface
+    /// should close.
+    close: *Surface,
 
     /// Quit
     quit: void,
 
-    /// A message for a specific window
-    window_message: struct {
-        window: *Window,
-        message: Window.Message,
+    /// A message for a specific surface.
+    surface_message: struct {
+        surface: *Surface,
+        message: apprt.surface.Message,
     },
 
+    /// Redraw a surface. This only has an effect for runtimes that
+    /// use single-threaded draws. To redraw a surface for all runtimes,
+    /// wake up the renderer thread. The renderer thread will send this
+    /// message if it needs to.
+    redraw_surface: *apprt.Surface,
+
     const NewWindow = struct {
-        /// Runtime-specific window options.
-        runtime: apprt.runtime.Window.Options = .{},
-
-        /// The parent window, only used for new tabs.
-        parent: ?*Window = null,
-
-        /// The font size to create the window with or null to default to
-        /// the configuration amount.
-        font_size: ?font.face.DesiredSize = null,
+        /// The parent surface
+        parent: ?*Surface = null,
     };
+
+    const NewTab = struct {
+        /// The parent surface
+        parent: ?*Surface = null,
+    };
+};
+
+/// Mailbox is the way that other threads send the app thread messages.
+pub const Mailbox = struct {
+    /// The type used for sending messages to the app thread.
+    pub const Queue = BlockingQueue(Message, 64);
+
+    rt_app: *apprt.App,
+    mailbox: *Queue,
+
+    /// Send a message to the surface.
+    pub fn push(self: Mailbox, msg: Message, timeout: Queue.Timeout) Queue.Size {
+        const result = self.mailbox.push(msg, timeout);
+
+        // Wake up our app loop
+        self.rt_app.wakeup();
+
+        return result;
+    }
 };
 
 // Wasm API.
@@ -335,147 +299,3 @@ pub const Wasm = if (!builtin.target.isWasm()) struct {} else struct {
     //     }
     // }
 };
-
-// C API
-pub const CAPI = struct {
-    const global = &@import("main.zig").state;
-
-    /// Create a new app.
-    export fn ghostty_app_new(
-        opts: *const apprt.runtime.App.Options,
-        config: *const Config,
-    ) ?*App {
-        return app_new_(opts, config) catch |err| {
-            log.err("error initializing app err={}", .{err});
-            return null;
-        };
-    }
-
-    fn app_new_(
-        opts: *const apprt.runtime.App.Options,
-        config: *const Config,
-    ) !*App {
-        const app = try App.create(global.alloc, opts.*, config);
-        errdefer app.destroy();
-        return app;
-    }
-
-    /// Tick the event loop. This should be called whenever the "wakeup"
-    /// callback is invoked for the runtime.
-    export fn ghostty_app_tick(v: *App) void {
-        v.tick() catch |err| {
-            log.err("error app tick err={}", .{err});
-        };
-    }
-
-    /// Return the userdata associated with the app.
-    export fn ghostty_app_userdata(v: *App) ?*anyopaque {
-        return v.runtime.opts.userdata;
-    }
-
-    export fn ghostty_app_free(ptr: ?*App) void {
-        if (ptr) |v| {
-            v.destroy();
-            v.alloc.destroy(v);
-        }
-    }
-
-    /// Create a new surface as part of an app.
-    export fn ghostty_surface_new(
-        app: *App,
-        opts: *const apprt.runtime.Window.Options,
-    ) ?*Window {
-        return surface_new_(app, opts) catch |err| {
-            log.err("error initializing surface err={}", .{err});
-            return null;
-        };
-    }
-
-    fn surface_new_(
-        app: *App,
-        opts: *const apprt.runtime.Window.Options,
-    ) !*Window {
-        const w = try app.newWindow(.{
-            .runtime = opts.*,
-        });
-        return w;
-    }
-
-    export fn ghostty_surface_free(ptr: ?*Window) void {
-        if (ptr) |v| v.app.closeWindow(v);
-    }
-
-    /// Returns the app associated with a surface.
-    export fn ghostty_surface_app(win: *Window) *App {
-        return win.app;
-    }
-
-    /// Tell the surface that it needs to schedule a render
-    export fn ghostty_surface_refresh(win: *Window) void {
-        win.window.refresh();
-    }
-
-    /// Update the size of a surface. This will trigger resize notifications
-    /// to the pty and the renderer.
-    export fn ghostty_surface_set_size(win: *Window, w: u32, h: u32) void {
-        win.window.updateSize(w, h);
-    }
-
-    /// Update the content scale of the surface.
-    export fn ghostty_surface_set_content_scale(win: *Window, x: f64, y: f64) void {
-        win.window.updateContentScale(x, y);
-    }
-
-    /// Update the focused state of a surface.
-    export fn ghostty_surface_set_focus(win: *Window, focused: bool) void {
-        win.window.focusCallback(focused);
-    }
-
-    /// Tell the surface that it needs to schedule a render
-    export fn ghostty_surface_key(
-        win: *Window,
-        action: input.Action,
-        key: input.Key,
-        mods: c_int,
-    ) void {
-        win.window.keyCallback(
-            action,
-            key,
-            @bitCast(input.Mods, @truncate(u8, @bitCast(c_uint, mods))),
-        );
-    }
-
-    /// Tell the surface that it needs to schedule a render
-    export fn ghostty_surface_char(win: *Window, codepoint: u32) void {
-        win.window.charCallback(codepoint);
-    }
-
-    /// Tell the surface that it needs to schedule a render
-    export fn ghostty_surface_mouse_button(
-        win: *Window,
-        action: input.MouseButtonState,
-        button: input.MouseButton,
-        mods: c_int,
-    ) void {
-        win.window.mouseButtonCallback(
-            action,
-            button,
-            @bitCast(input.Mods, @truncate(u8, @bitCast(c_uint, mods))),
-        );
-    }
-
-    /// Update the mouse position within the view.
-    export fn ghostty_surface_mouse_pos(win: *Window, x: f64, y: f64) void {
-        win.window.cursorPosCallback(x, y);
-    }
-
-    export fn ghostty_surface_mouse_scroll(win: *Window, x: f64, y: f64) void {
-        win.window.scrollCallback(x, y);
-    }
-
-    export fn ghostty_surface_ime_point(win: *Window, x: *f64, y: *f64) void {
-        const pos = win.imePoint();
-        x.* = pos.x;
-        y.* = pos.y;
-    }
-};
diff --git a/src/DevMode.zig b/src/DevMode.zig
index 2b037ce2a..bd28366ca 100644
--- a/src/DevMode.zig
+++ b/src/DevMode.zig
@@ -10,7 +10,7 @@ const Allocator = std.mem.Allocator;
 const assert = std.debug.assert;
 
 const font = @import("font/main.zig");
-const Window = @import("Window.zig");
+const Surface = @import("Surface.zig");
 const renderer = @import("renderer.zig");
 const Config = @import("config.zig").Config;
 
@@ -29,8 +29,8 @@ visible: bool = false,
 /// Our app config
 config: ?*const Config = null,
 
-/// The window we're tracking.
-window: ?*Window = null,
+/// The surface we're tracking.
+surface: ?*Surface = null,
 
 /// Update the state associated with the dev mode. This should generally
 /// only be called paired with a render since it otherwise wastes CPU
@@ -86,20 +86,20 @@ pub fn update(self: *const DevMode) !void {
             }
         }
 
-        if (self.window) |window| {
+        if (self.surface) |surface| {
             if (imgui.collapsingHeader("Font Manager", null, .{})) {
-                imgui.text("Glyphs: %d", window.font_group.glyphs.count());
+                imgui.text("Glyphs: %d", surface.font_group.glyphs.count());
                 imgui.sameLine(0, -1);
                 helpMarker("The number of glyphs loaded and rendered into a " ++
                     "font atlas currently.");
 
-                const Renderer = @TypeOf(window.renderer);
+                const Renderer = @TypeOf(surface.renderer);
                 if (imgui.treeNode("Atlas: Greyscale", .{ .default_open = true })) {
                     defer imgui.treePop();
-                    const atlas = &window.font_group.atlas_greyscale;
+                    const atlas = &surface.font_group.atlas_greyscale;
                     const tex = switch (Renderer) {
-                        renderer.OpenGL => @intCast(usize, window.renderer.texture.id),
-                        renderer.Metal => @ptrToInt(window.renderer.texture_greyscale.value),
+                        renderer.OpenGL => @intCast(usize, surface.renderer.texture.id),
+                        renderer.Metal => @ptrToInt(surface.renderer.texture_greyscale.value),
                         else => @compileError("renderer unsupported, add it!"),
                     };
                     try self.atlasInfo(atlas, tex);
@@ -107,10 +107,10 @@ pub fn update(self: *const DevMode) !void {
 
                 if (imgui.treeNode("Atlas: Color (Emoji)", .{ .default_open = true })) {
                     defer imgui.treePop();
-                    const atlas = &window.font_group.atlas_color;
+                    const atlas = &surface.font_group.atlas_color;
                     const tex = switch (Renderer) {
-                        renderer.OpenGL => @intCast(usize, window.renderer.texture_color.id),
-                        renderer.Metal => @ptrToInt(window.renderer.texture_color.value),
+                        renderer.OpenGL => @intCast(usize, surface.renderer.texture_color.id),
+                        renderer.Metal => @ptrToInt(surface.renderer.texture_color.value),
                         else => @compileError("renderer unsupported, add it!"),
                     };
                     try self.atlasInfo(atlas, tex);
diff --git a/src/Window.zig b/src/Surface.zig
similarity index 87%
rename from src/Window.zig
rename to src/Surface.zig
index a769343fc..b7ce3ede7 100644
--- a/src/Window.zig
+++ b/src/Surface.zig
@@ -1,15 +1,19 @@
-//! Window represents a single OS window.
+//! Surface represents a single terminal "surface". A terminal surface is
+//! a minimal "widget" where the terminal is drawn and responds to events
+//! such as keyboard and mouse. Each surface also creates and owns its pty
+//! session.
 //!
-//! NOTE(multi-window): This may be premature, but this abstraction is here
-//! to pave the way One Day(tm) for multi-window support. At the time of
-//! writing, we support exactly one window.
-const Window = @This();
+//! The word "surface" is used because it is left to the higher level
+//! application runtime to determine if the surface is a window, a tab,
+//! a split, a preview pane in a larger window, etc. This struct doesn't care:
+//! it just draws and responds to events. The events come from the application
+//! runtime so the runtime can determine when and how those are delivered
+//! (i.e. with focus, without focus, and so on).
+const Surface = @This();
 
-// TODO: eventually, I want to extract Window.zig into the "window" package
-// so we can also have alternate implementations (i.e. not glfw).
 const apprt = @import("apprt.zig");
-pub const Mailbox = apprt.Window.Mailbox;
-pub const Message = apprt.Window.Message;
+pub const Mailbox = apprt.surface.Mailbox;
+pub const Message = apprt.surface.Message;
 
 const std = @import("std");
 const builtin = @import("builtin");
@@ -18,7 +22,6 @@ const Allocator = std.mem.Allocator;
 const renderer = @import("renderer.zig");
 const termio = @import("termio.zig");
 const objc = @import("objc");
-const glfw = @import("glfw");
 const imgui = @import("imgui");
 const Pty = @import("Pty.zig");
 const font = @import("font/main.zig");
@@ -31,12 +34,7 @@ const DevMode = @import("DevMode.zig");
 const App = @import("App.zig");
 const internal_os = @import("os/main.zig");
 
-// Get native API access on certain platforms so we can do more customization.
-const glfwNative = glfw.Native(.{
-    .cocoa = builtin.target.isDarwin(),
-});
-
-const log = std.log.scoped(.window);
+const log = std.log.scoped(.surface);
 
 // The renderer implementation to use.
 const Renderer = renderer.Renderer;
@@ -44,11 +42,11 @@ const Renderer = renderer.Renderer;
 /// Allocator
 alloc: Allocator,
 
-/// The app that this window is a part of.
-app: *App,
+/// The mailbox for sending messages to the main app thread.
+app_mailbox: App.Mailbox,
 
-/// The windowing system state
-window: apprt.runtime.Window,
+/// The windowing system surface
+rt_surface: *apprt.runtime.Surface,
 
 /// The font structures
 font_lib: font.Library,
@@ -58,7 +56,7 @@ font_size: font.face.DesiredSize,
 /// Imgui context
 imgui_ctx: if (DevMode.enabled) *imgui.Context else void,
 
-/// The renderer for this window.
+/// The renderer for this surface.
 renderer: Renderer,
 
 /// The render state
@@ -96,7 +94,7 @@ config: *const Config,
 /// like such as "control-v" will write a "v" even if they're intercepted.
 ignore_char: bool = false,
 
-/// Mouse state for the window.
+/// Mouse state for the surface.
 const Mouse = struct {
     /// The last tracked mouse button state by button.
     click_state: [input.MouseButton.max]input.MouseButtonState = .{.release} ** input.MouseButton.max,
@@ -111,7 +109,7 @@ const Mouse = struct {
 
     /// The starting xpos/ypos of the left click. Note that if scrolling occurs,
     /// these will point to different "cells", but the xpos/ypos will stay
-    /// stable during scrolling relative to the window.
+    /// stable during scrolling relative to the surface.
     left_click_xpos: f64 = 0,
     left_click_ypos: f64 = 0,
 
@@ -125,28 +123,22 @@ const Mouse = struct {
     event_point: terminal.point.Viewport = .{},
 };
 
-/// Create a new window. This allocates and returns a pointer because we
-/// need a stable pointer for user data callbacks. Therefore, a stack-only
-/// initialization is not currently possible.
-pub fn create(
+/// Create a new surface. This must be called from the main thread. The
+/// pointer to the memory for the surface must be provided and must be
+/// stable due to interfacing with various callbacks.
+pub fn init(
+    self: *Surface,
     alloc: Allocator,
-    app: *App,
     config: *const Config,
-    rt_opts: apprt.runtime.Window.Options,
-) !*Window {
-    var self = try alloc.create(Window);
-    errdefer alloc.destroy(self);
-
-    // Create the windowing system
-    var window = try apprt.runtime.Window.init(app, self, rt_opts);
-    errdefer window.deinit();
-
-    // Initialize our renderer with our initialized windowing system.
-    try Renderer.windowInit(window);
+    app_mailbox: App.Mailbox,
+    rt_surface: *apprt.runtime.Surface,
+) !void {
+    // Initialize our renderer with our initialized surface.
+    try Renderer.surfaceInit(rt_surface);
 
     // Determine our DPI configurations so we can properly configure
     // font points to pixels and handle other high-DPI scaling factors.
-    const content_scale = try window.getContentScale();
+    const content_scale = try rt_surface.getContentScale();
     const x_dpi = content_scale.x * font.face.default_dpi;
     const y_dpi = content_scale.y * font.face.default_dpi;
     log.debug("xscale={} yscale={} xdpi={} ydpi={}", .{
@@ -156,17 +148,17 @@ pub fn create(
         y_dpi,
     });
 
-    // The font size we desire along with the DPI determiend for the window
+    // The font size we desire along with the DPI determined for the surface
     const font_size: font.face.DesiredSize = .{
         .points = config.@"font-size",
         .xdpi = @floatToInt(u16, x_dpi),
         .ydpi = @floatToInt(u16, y_dpi),
     };
 
-    // Find all the fonts for this window
+    // Find all the fonts for this surface
     //
-    // Future: we can share the font group amongst all windows to save
-    // some new window init time and some memory. This will require making
+    // Future: we can share the font group amongst all surfaces to save
+    // some new surface init time and some memory. This will require making
     // thread-safe changes to font structs.
     var font_lib = try font.Library.init();
     errdefer font_lib.deinit();
@@ -290,7 +282,7 @@ pub fn create(
         .left = padding_x,
     };
 
-    // Create our terminal grid with the initial window size
+    // Create our terminal grid with the initial size
     var renderer_impl = try Renderer.init(alloc, .{
         .config = config,
         .font_group = font_group,
@@ -298,15 +290,15 @@ pub fn create(
             .explicit = padding,
             .balance = config.@"window-padding-balance",
         },
-        .window_mailbox = .{ .window = self, .app = app.mailbox },
+        .surface_mailbox = .{ .surface = self, .app = app_mailbox },
     });
     errdefer renderer_impl.deinit();
 
     // Calculate our grid size based on known dimensions.
-    const window_size = try window.getSize();
+    const surface_size = try rt_surface.getSize();
     const screen_size: renderer.ScreenSize = .{
-        .width = window_size.width,
-        .height = window_size.height,
+        .width = surface_size.width,
+        .height = surface_size.height,
     };
     const grid_size = renderer.GridSize.init(
         screen_size.subPadding(padding),
@@ -321,9 +313,10 @@ pub fn create(
     // Create the renderer thread
     var render_thread = try renderer.Thread.init(
         alloc,
-        window,
+        rt_surface,
         &self.renderer,
         &self.renderer_state,
+        app_mailbox,
     );
     errdefer render_thread.deinit();
 
@@ -335,7 +328,7 @@ pub fn create(
         .renderer_state = &self.renderer_state,
         .renderer_wakeup = render_thread.wakeup,
         .renderer_mailbox = render_thread.mailbox,
-        .window_mailbox = .{ .window = self, .app = app.mailbox },
+        .surface_mailbox = .{ .surface = self, .app = app_mailbox },
     });
     errdefer io.deinit();
 
@@ -343,15 +336,15 @@ pub fn create(
     var io_thread = try termio.Thread.init(alloc, &self.io);
     errdefer io_thread.deinit();
 
-    // True if this window is hosting devmode. We only host devmode on
-    // the first window since imgui is not threadsafe. We need to do some
+    // True if this surface is hosting devmode. We only host devmode on
+    // the first surface since imgui is not threadsafe. We need to do some
     // work to make DevMode work with multiple threads.
-    const host_devmode = DevMode.enabled and DevMode.instance.window == null;
+    const host_devmode = DevMode.enabled and DevMode.instance.surface == null;
 
     self.* = .{
         .alloc = alloc,
-        .app = app,
-        .window = window,
+        .app_mailbox = app_mailbox,
+        .rt_surface = rt_surface,
         .font_lib = font_lib,
         .font_group = font_group,
         .font_size = font_size,
@@ -384,21 +377,21 @@ pub fn create(
 
     // Set a minimum size that is cols=10 h=4. This matches Mac's Terminal.app
     // but is otherwise somewhat arbitrary.
-    try window.setSizeLimits(.{
+    try rt_surface.setSizeLimits(.{
         .width = @floatToInt(u32, cell_size.width * 10),
         .height = @floatToInt(u32, cell_size.height * 4),
     }, null);
 
     // Call our size callback which handles all our retina setup
-    // Note: this shouldn't be necessary and when we clean up the window
+    // Note: this shouldn't be necessary and when we clean up the surface
     // init stuff we should get rid of this. But this is required because
     // sizeCallback does retina-aware stuff we don't do here and don't want
     // to duplicate.
-    try self.sizeCallback(window_size);
+    try self.sizeCallback(surface_size);
 
     // Load imgui. This must be done LAST because it has to be done after
     // all our GLFW setup is complete.
-    if (DevMode.enabled and DevMode.instance.window == null) {
+    if (DevMode.enabled and DevMode.instance.surface == null) {
         const dev_io = try imgui.IO.get();
         dev_io.cval().IniFilename = "ghostty_dev_mode.ini";
 
@@ -413,16 +406,16 @@ pub fn create(
         const style = try imgui.Style.get();
         style.colorsDark();
 
-        // Add our window to the instance if it isn't set.
-        DevMode.instance.window = self;
+        // Add our surface to the instance if it isn't set.
+        DevMode.instance.surface = self;
 
         // Let our renderer setup
-        try renderer_impl.initDevMode(window);
+        try renderer_impl.initDevMode(rt_surface);
     }
 
-    // Give the renderer one more opportunity to finalize any window
+    // Give the renderer one more opportunity to finalize any surface
     // setup on the main thread prior to spinning up the rendering thread.
-    try renderer_impl.finalizeWindowInit(window);
+    try renderer_impl.finalizeSurfaceInit(rt_surface);
 
     // Start our renderer thread
     self.renderer_thr = try std.Thread.spawn(
@@ -439,11 +432,9 @@ pub fn create(
         .{&self.io_thread},
     );
     self.io_thr.setName("io") catch {};
-
-    return self;
 }
 
-pub fn destroy(self: *Window) void {
+pub fn deinit(self: *Surface) void {
     // Stop rendering thread
     {
         self.renderer_thread.stop.notify() catch |err|
@@ -451,15 +442,15 @@ pub fn destroy(self: *Window) void {
         self.renderer_thr.join();
 
         // We need to become the active rendering thread again
-        self.renderer.threadEnter(self.window) catch unreachable;
+        self.renderer.threadEnter(self.rt_surface) catch unreachable;
 
         // If we are devmode-owning, clean that up.
-        if (DevMode.enabled and DevMode.instance.window == self) {
+        if (DevMode.enabled and DevMode.instance.surface == self) {
             // Let our renderer clean up
             self.renderer.deinitDevMode();
 
-            // Clear the window
-            DevMode.instance.window = null;
+            // Clear the surface
+            DevMode.instance.surface = null;
 
             // Uninitialize imgui
             self.imgui_ctx.destroy();
@@ -480,62 +471,23 @@ pub fn destroy(self: *Window) void {
     self.io_thread.deinit();
     self.io.deinit();
 
-    self.window.deinit();
-
     self.font_group.deinit(self.alloc);
     self.font_lib.deinit();
     self.alloc.destroy(self.font_group);
 
     self.alloc.destroy(self.renderer_state.mutex);
-
-    self.alloc.destroy(self);
-}
-
-pub fn shouldClose(self: Window) bool {
-    return self.window.shouldClose();
-}
-
-/// Add a window to the tab group of this window.
-pub fn addWindow(self: *Window, other: *Window) void {
-    assert(builtin.target.isDarwin());
-
-    // This has a hard dependency on GLFW currently. If we want to support
-    // this in other windowing systems we should abstract this. This is NOT
-    // the right interface.
-    const self_win = glfwNative.getCocoaWindow(self.window.window).?;
-    const other_win = glfwNative.getCocoaWindow(other.window.window).?;
-
-    const NSWindowOrderingMode = enum(isize) { below = -1, out = 0, above = 1 };
-    const nswindow = objc.Object.fromId(self_win);
-    nswindow.msgSend(void, objc.sel("addTabbedWindow:ordered:"), .{
-        objc.Object.fromId(other_win),
-        NSWindowOrderingMode.above,
-    });
-
-    // Adding a new tab can cause the tab bar to appear which changes
-    // our viewport size. We need to call the size callback in order to
-    // update values. For example, we need this to set the proper mouse selection
-    // point in the grid.
-    const size = self.window.getSize() catch |err| {
-        log.err("error querying window size for size callback on new tab err={}", .{err});
-        return;
-    };
-    self.sizeCallback(size) catch |err| {
-        log.err("error in size callback from new tab err={}", .{err});
-        return;
-    };
 }
 
 /// Called from the app thread to handle mailbox messages to our specific
-/// window.
-pub fn handleMessage(self: *Window, msg: Message) !void {
+/// surface.
+pub fn handleMessage(self: *Surface, msg: Message) !void {
     switch (msg) {
         .set_title => |*v| {
             // The ptrCast just gets sliceTo to return the proper type.
             // We know that our title should end in 0.
             const slice = std.mem.sliceTo(@ptrCast([*:0]const u8, v), 0);
             log.debug("changing title \"{s}\"", .{slice});
-            try self.window.setTitle(slice);
+            try self.rt_surface.setTitle(slice);
         },
 
         .cell_size => |size| try self.setCellSize(size),
@@ -555,7 +507,7 @@ pub fn handleMessage(self: *Window, msg: Message) !void {
 
 /// Returns the x/y coordinate of where the IME (Input Method Editor)
 /// keyboard should be rendered.
-pub fn imePoint(self: *const Window) apprt.IMEPos {
+pub fn imePoint(self: *const Surface) apprt.IMEPos {
     self.renderer_state.mutex.lock();
     const cursor = self.renderer_state.terminal.screen.cursor;
     self.renderer_state.mutex.unlock();
@@ -564,7 +516,7 @@ pub fn imePoint(self: *const Window) apprt.IMEPos {
     // in the visible portion of the screen.
 
     // Our sizes are all scaled so we need to send the unscaled values back.
-    const content_scale = self.window.getContentScale() catch .{ .x = 1, .y = 1 };
+    const content_scale = self.rt_surface.getContentScale() catch .{ .x = 1, .y = 1 };
 
     const x: f64 = x: {
         // Simple x * cell width gives the top-left corner
@@ -595,13 +547,13 @@ pub fn imePoint(self: *const Window) apprt.IMEPos {
     return .{ .x = x, .y = y };
 }
 
-fn clipboardRead(self: *const Window, kind: u8) !void {
+fn clipboardRead(self: *const Surface, kind: u8) !void {
     if (!self.config.@"clipboard-read") {
         log.info("application attempted to read clipboard, but 'clipboard-read' setting is off", .{});
         return;
     }
 
-    const data = self.window.getClipboardString() catch |err| {
+    const data = self.rt_surface.getClipboardString() catch |err| {
         log.warn("error reading clipboard: {}", .{err});
         return;
     };
@@ -631,7 +583,7 @@ fn clipboardRead(self: *const Window, kind: u8) !void {
     self.io_thread.wakeup.notify() catch {};
 }
 
-fn clipboardWrite(self: *const Window, data: []const u8) !void {
+fn clipboardWrite(self: *const Surface, data: []const u8) !void {
     if (!self.config.@"clipboard-write") {
         log.info("application attempted to write clipboard, but 'clipboard-write' setting is off", .{});
         return;
@@ -649,7 +601,7 @@ fn clipboardWrite(self: *const Window, data: []const u8) !void {
     try dec.decode(buf, data);
     assert(buf[buf.len] == 0);
 
-    self.window.setClipboardString(buf) catch |err| {
+    self.rt_surface.setClipboardString(buf) catch |err| {
         log.err("error setting clipboard string err={}", .{err});
         return;
     };
@@ -657,7 +609,7 @@ fn clipboardWrite(self: *const Window, data: []const u8) !void {
 
 /// Change the cell size for the terminal grid. This can happen as
 /// a result of changing the font size at runtime.
-fn setCellSize(self: *Window, size: renderer.CellSize) !void {
+fn setCellSize(self: *Surface, size: renderer.CellSize) !void {
     // Update our new cell size for future calcs
     self.cell_size = size;
 
@@ -681,7 +633,7 @@ fn setCellSize(self: *Window, size: renderer.CellSize) !void {
 /// Change the font size.
 ///
 /// This can only be called from the main thread.
-pub fn setFontSize(self: *Window, size: font.face.DesiredSize) void {
+pub fn setFontSize(self: *Surface, size: font.face.DesiredSize) void {
     // Update our font size so future changes work
     self.font_size = size;
 
@@ -697,11 +649,11 @@ pub fn setFontSize(self: *Window, size: font.face.DesiredSize) void {
 /// This queues a render operation with the renderer thread. The render
 /// isn't guaranteed to happen immediately but it will happen as soon as
 /// practical.
-fn queueRender(self: *const Window) !void {
+fn queueRender(self: *const Surface) !void {
     try self.renderer_thread.wakeup.notify();
 }
 
-pub fn sizeCallback(self: *Window, size: apprt.WindowSize) !void {
+pub fn sizeCallback(self: *Surface, size: apprt.SurfaceSize) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
@@ -745,7 +697,7 @@ pub fn sizeCallback(self: *Window, size: apprt.WindowSize) !void {
     try self.io_thread.wakeup.notify();
 }
 
-pub fn charCallback(self: *Window, codepoint: u21) !void {
+pub fn charCallback(self: *Surface, codepoint: u21) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
@@ -796,7 +748,7 @@ pub fn charCallback(self: *Window, codepoint: u21) !void {
 }
 
 pub fn keyCallback(
-    self: *Window,
+    self: *Surface,
     action: input.Action,
     key: input.Key,
     mods: input.Mods,
@@ -879,7 +831,7 @@ pub fn keyCallback(
                         };
                         defer self.alloc.free(buf);
 
-                        self.window.setClipboardString(buf) catch |err| {
+                        self.rt_surface.setClipboardString(buf) catch |err| {
                             log.err("error setting clipboard string err={}", .{err});
                             return;
                         };
@@ -887,7 +839,7 @@ pub fn keyCallback(
                 },
 
                 .paste_from_clipboard => {
-                    const data = self.window.getClipboardString() catch |err| {
+                    const data = self.rt_surface.getClipboardString() catch |err| {
                         log.warn("error reading clipboard: {}", .{err});
                         return;
                     };
@@ -950,38 +902,29 @@ pub fn keyCallback(
                 } else log.warn("dev mode was not compiled into this binary", .{}),
 
                 .new_window => {
-                    _ = self.app.mailbox.push(.{
+                    _ = self.app_mailbox.push(.{
                         .new_window = .{
-                            .font_size = if (self.config.@"window-inherit-font-size")
-                                self.font_size
-                            else
-                                null,
+                            .parent = self,
                         },
                     }, .{ .instant = {} });
-                    self.app.wakeup();
                 },
 
                 .new_tab => {
-                    _ = self.app.mailbox.push(.{
+                    _ = self.app_mailbox.push(.{
                         .new_tab = .{
                             .parent = self,
-
-                            .font_size = if (self.config.@"window-inherit-font-size")
-                                self.font_size
-                            else
-                                null,
                         },
                     }, .{ .instant = {} });
-                    self.app.wakeup();
                 },
 
-                .close_window => self.window.setShouldClose(),
+                .close_window => {
+                    _ = self.app_mailbox.push(.{ .close = self }, .{ .instant = {} });
+                },
 
                 .quit => {
-                    _ = self.app.mailbox.push(.{
+                    _ = self.app_mailbox.push(.{
                         .quit = {},
                     }, .{ .instant = {} });
-                    self.app.wakeup();
                 },
             }
 
@@ -1059,7 +1002,7 @@ pub fn keyCallback(
     }
 }
 
-pub fn focusCallback(self: *Window, focused: bool) !void {
+pub fn focusCallback(self: *Surface, focused: bool) !void {
     // Notify our render thread of the new state
     _ = self.renderer_thread.mailbox.push(.{
         .focus = focused,
@@ -1069,17 +1012,17 @@ pub fn focusCallback(self: *Window, focused: bool) !void {
     try self.queueRender();
 }
 
-pub fn refreshCallback(self: *Window) !void {
+pub fn refreshCallback(self: *Surface) !void {
     // The point of this callback is to schedule a render, so do that.
     try self.queueRender();
 }
 
-pub fn scrollCallback(self: *Window, xoff: f64, yoff: f64) !void {
+pub fn scrollCallback(self: *Surface, xoff: f64, yoff: f64) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    // If our dev mode window is visible then we always schedule a render on
-    // cursor move because the cursor might touch our windows.
+    // If our dev mode surface is visible then we always schedule a render on
+    // cursor move because the cursor might touch our surfaces.
     if (DevMode.enabled and DevMode.instance.visible) {
         try self.queueRender();
 
@@ -1107,7 +1050,7 @@ pub fn scrollCallback(self: *Window, xoff: f64, yoff: f64) !void {
         // If we're scrolling up or down, then send a mouse event. This requires
         // a lock since we read terminal state.
         if (yoff != 0) {
-            const pos = try self.window.getCursorPos();
+            const pos = try self.rt_surface.getCursorPos();
             try self.mouseReport(if (yoff < 0) .five else .four, .press, self.mouse.mods, pos);
         }
     }
@@ -1119,14 +1062,14 @@ pub fn scrollCallback(self: *Window, xoff: f64, yoff: f64) !void {
 const MouseReportAction = enum { press, release, motion };
 
 fn mouseReport(
-    self: *Window,
+    self: *Surface,
     button: ?input.MouseButton,
     action: MouseReportAction,
     mods: input.Mods,
     pos: apprt.CursorPos,
 ) !void {
-    // TODO: posToViewport currently clamps to the window boundary,
-    // do we want to not report mouse events at all outside the window?
+    // TODO: posToViewport currently clamps to the surface boundary,
+    // do we want to not report mouse events at all outside the surface?
 
     // Depending on the event, we may do nothing at all.
     switch (self.io.terminal.modes.mouse_event) {
@@ -1314,7 +1257,7 @@ fn mouseReport(
 }
 
 pub fn mouseButtonCallback(
-    self: *Window,
+    self: *Surface,
     action: input.MouseButtonState,
     button: input.MouseButton,
     mods: input.Mods,
@@ -1322,8 +1265,8 @@ pub fn mouseButtonCallback(
     const tracy = trace(@src());
     defer tracy.end();
 
-    // If our dev mode window is visible then we always schedule a render on
-    // cursor move because the cursor might touch our windows.
+    // If our dev mode surface is visible then we always schedule a render on
+    // cursor move because the cursor might touch our surfaces.
     if (DevMode.enabled and DevMode.instance.visible) {
         try self.queueRender();
 
@@ -1342,7 +1285,7 @@ pub fn mouseButtonCallback(
 
     // Report mouse events if enabled
     if (self.io.terminal.modes.mouse_event != .none) {
-        const pos = try self.window.getCursorPos();
+        const pos = try self.rt_surface.getCursorPos();
 
         const report_action: MouseReportAction = switch (action) {
             .press => .press,
@@ -1360,7 +1303,7 @@ pub fn mouseButtonCallback(
     // For left button clicks we always record some information for
     // selection/highlighting purposes.
     if (button == .left and action == .press) {
-        const pos = try self.window.getCursorPos();
+        const pos = try self.rt_surface.getCursorPos();
 
         // If we move our cursor too much between clicks then we reset
         // the multi-click state.
@@ -1433,14 +1376,14 @@ pub fn mouseButtonCallback(
 }
 
 pub fn cursorPosCallback(
-    self: *Window,
+    self: *Surface,
     pos: apprt.CursorPos,
 ) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    // If our dev mode window is visible then we always schedule a render on
-    // cursor move because the cursor might touch our windows.
+    // If our dev mode surface is visible then we always schedule a render on
+    // cursor move because the cursor might touch our surfaces.
     if (DevMode.enabled and DevMode.instance.visible) {
         try self.queueRender();
 
@@ -1495,7 +1438,7 @@ pub fn cursorPosCallback(
 
 /// Double-click dragging moves the selection one "word" at a time.
 fn dragLeftClickDouble(
-    self: *Window,
+    self: *Surface,
     screen_point: terminal.point.ScreenPoint,
 ) void {
     // Get the word under our current point. If there isn't a word, do nothing.
@@ -1520,7 +1463,7 @@ fn dragLeftClickDouble(
 
 /// Triple-click dragging moves the selection one "line" at a time.
 fn dragLeftClickTriple(
-    self: *Window,
+    self: *Surface,
     screen_point: terminal.point.ScreenPoint,
 ) void {
     // Get the word under our current point. If there isn't a word, do nothing.
@@ -1544,7 +1487,7 @@ fn dragLeftClickTriple(
 }
 
 fn dragLeftClickSingle(
-    self: *Window,
+    self: *Surface,
     screen_point: terminal.point.ScreenPoint,
     xpos: f64,
 ) void {
@@ -1650,10 +1593,10 @@ fn dragLeftClickSingle(
     self.io.terminal.selection.?.end = screen_point;
 }
 
-fn posToViewport(self: Window, xpos: f64, ypos: f64) terminal.point.Viewport {
+fn posToViewport(self: Surface, xpos: f64, ypos: f64) terminal.point.Viewport {
     // xpos and ypos can be negative if while dragging, the user moves the
-    // mouse off the window. Likewise, they can be larger than our window
-    // width if the user drags out of the window positively.
+    // mouse off the surface. Likewise, they can be larger than our surface
+    // width if the user drags out of the surface positively.
     return .{
         .x = if (xpos < 0) 0 else x: {
             // Our cell is the mouse divided by cell width
diff --git a/src/apprt.zig b/src/apprt.zig
index 36e2a2571..01aea84e8 100644
--- a/src/apprt.zig
+++ b/src/apprt.zig
@@ -8,25 +8,56 @@
 //! The goal is to have different implementations share as much of the core
 //! logic as possible, and to only reach out to platform-specific implementation
 //! code when absolutely necessary.
+const std = @import("std");
 const builtin = @import("builtin");
 const build_config = @import("build_config.zig");
 
 pub usingnamespace @import("apprt/structs.zig");
 pub const glfw = @import("apprt/glfw.zig");
+pub const gtk = @import("apprt/gtk.zig");
 pub const browser = @import("apprt/browser.zig");
 pub const embedded = @import("apprt/embedded.zig");
-pub const Window = @import("apprt/Window.zig");
+pub const surface = @import("apprt/surface.zig");
 
 /// The implementation to use for the app runtime. This is comptime chosen
 /// so that every build has exactly one application runtime implementation.
 /// Note: it is very rare to use Runtime directly; most usage will use
 /// Window or something.
 pub const runtime = switch (build_config.artifact) {
-    .exe => glfw,
+    .exe => switch (build_config.app_runtime) {
+        .none => @compileError("exe with no runtime not allowed"),
+        .glfw => glfw,
+        .gtk => gtk,
+    },
     .lib => embedded,
     .wasm_module => browser,
 };
 
+pub const App = runtime.App;
+pub const Surface = runtime.Surface;
+
+/// Runtime is the runtime to use for Ghostty. All runtimes do not provide
+/// equivalent feature sets. For example, GTK offers tabbing and more features
+/// that glfw does not provide. However, glfw may require many less
+/// dependencies.
+pub const Runtime = enum {
+    /// Will not produce an executable at all when `zig build` is called.
+    /// This is only useful if you're only interested in the lib only (macOS).
+    none,
+
+    /// Glfw-backed. Very simple. Glfw is statically linked. Tabbing and
+    /// other rich windowing features are not supported.
+    glfw,
+
+    /// GTK-backed. Rich windowed application. GTK is dynamically linked.
+    gtk,
+
+    pub fn default(target: std.zig.CrossTarget) Runtime {
+        _ = target;
+        return .glfw;
+    }
+};
+
 test {
     @import("std").testing.refAllDecls(@This());
 }
diff --git a/src/apprt/embedded.zig b/src/apprt/embedded.zig
index 663860977..8db67b0a1 100644
--- a/src/apprt/embedded.zig
+++ b/src/apprt/embedded.zig
@@ -12,7 +12,7 @@ const objc = @import("objc");
 const apprt = @import("../apprt.zig");
 const input = @import("../input.zig");
 const CoreApp = @import("../App.zig");
-const CoreWindow = @import("../Window.zig");
+const CoreSurface = @import("../Surface.zig");
 
 const log = std.log.scoped(.embedded_window);
 
@@ -46,30 +46,57 @@ pub const App = struct {
         write_clipboard: *const fn (SurfaceUD, [*:0]const u8) callconv(.C) void,
     };
 
+    core_app: *CoreApp,
     opts: Options,
 
-    pub fn init(opts: Options) !App {
-        return .{ .opts = opts };
+    pub fn init(core_app: *CoreApp, opts: Options) !App {
+        return .{ .core_app = core_app, .opts = opts };
     }
 
     pub fn terminate(self: App) void {
         _ = self;
     }
 
-    pub fn wakeup(self: App) !void {
+    pub fn wakeup(self: App) void {
         self.opts.wakeup(self.opts.userdata);
     }
 
     pub fn wait(self: App) !void {
         _ = self;
     }
+
+    /// Create a new surface for the app.
+    fn newSurface(self: *App, opts: Surface.Options) !*Surface {
+        // Grab a surface allocation because we're going to need it.
+        var surface = try self.core_app.alloc.create(Surface);
+        errdefer self.core_app.alloc.destroy(surface);
+
+        // Create the surface -- because windows are surfaces for glfw.
+        try surface.init(self, opts);
+        errdefer surface.deinit();
+
+        return surface;
+    }
+
+    /// Close the given surface.
+    pub fn closeSurface(self: *App, surface: *Surface) void {
+        surface.deinit();
+        self.core_app.alloc.destroy(surface);
+    }
+
+    pub fn redrawSurface(self: *App, surface: *Surface) void {
+        _ = self;
+        _ = surface;
+        // No-op, we use a threaded interface so we're constantly drawing.
+    }
 };
 
-pub const Window = struct {
+pub const Surface = struct {
+    app: *App,
     nsview: objc.Object,
-    core_win: *CoreWindow,
+    core_surface: CoreSurface,
     content_scale: apprt.ContentScale,
-    size: apprt.WindowSize,
+    size: apprt.SurfaceSize,
     cursor_pos: apprt.CursorPos,
     opts: Options,
 
@@ -84,11 +111,10 @@ pub const Window = struct {
         scale_factor: f64 = 1,
     };
 
-    pub fn init(app: *const CoreApp, core_win: *CoreWindow, opts: Options) !Window {
-        _ = app;
-
-        return .{
-            .core_win = core_win,
+    pub fn init(self: *Surface, app: *App, opts: Options) !void {
+        self.* = .{
+            .app = app,
+            .core_surface = undefined,
             .nsview = objc.Object.fromId(opts.nsview),
             .content_scale = .{
                 .x = @floatCast(f32, opts.scale_factor),
@@ -98,104 +124,122 @@ pub const Window = struct {
             .cursor_pos = .{ .x = 0, .y = 0 },
             .opts = opts,
         };
+
+        // Add ourselves to the list of surfaces on the app.
+        try app.core_app.addSurface(self);
+        errdefer app.core_app.deleteSurface(self);
+
+        // Initialize our surface right away. We're given a view that is
+        // ready to use.
+        try self.core_surface.init(
+            app.core_app.alloc,
+            app.core_app.config,
+            .{ .rt_app = app, .mailbox = &app.core_app.mailbox },
+            self,
+        );
+        errdefer self.core_surface.deinit();
     }
 
-    pub fn deinit(self: *Window) void {
-        _ = self;
+    pub fn deinit(self: *Surface) void {
+        // Remove ourselves from the list of known surfaces in the app.
+        self.app.core_app.deleteSurface(self);
+
+        // Clean up our core surface so that all the rendering and IO stop.
+        self.core_surface.deinit();
     }
 
-    pub fn getContentScale(self: *const Window) !apprt.ContentScale {
+    pub fn getContentScale(self: *const Surface) !apprt.ContentScale {
         return self.content_scale;
     }
 
-    pub fn getSize(self: *const Window) !apprt.WindowSize {
+    pub fn getSize(self: *const Surface) !apprt.SurfaceSize {
         return self.size;
     }
 
-    pub fn setSizeLimits(self: *Window, min: apprt.WindowSize, max_: ?apprt.WindowSize) !void {
+    pub fn setSizeLimits(self: *Surface, min: apprt.SurfaceSize, max_: ?apprt.SurfaceSize) !void {
         _ = self;
         _ = min;
         _ = max_;
     }
 
-    pub fn setTitle(self: *Window, slice: [:0]const u8) !void {
-        self.core_win.app.runtime.opts.set_title(
+    pub fn setTitle(self: *Surface, slice: [:0]const u8) !void {
+        self.app.opts.set_title(
             self.opts.userdata,
             slice.ptr,
         );
     }
 
-    pub fn getClipboardString(self: *const Window) ![:0]const u8 {
-        const ptr = self.core_win.app.runtime.opts.read_clipboard(self.opts.userdata);
+    pub fn getClipboardString(self: *const Surface) ![:0]const u8 {
+        const ptr = self.app.opts.read_clipboard(self.opts.userdata);
         return std.mem.sliceTo(ptr, 0);
     }
 
-    pub fn setClipboardString(self: *const Window, val: [:0]const u8) !void {
-        self.core_win.app.runtime.opts.write_clipboard(self.opts.userdata, val.ptr);
+    pub fn setClipboardString(self: *const Surface, val: [:0]const u8) !void {
+        self.app.opts.write_clipboard(self.opts.userdata, val.ptr);
     }
 
-    pub fn setShouldClose(self: *Window) void {
+    pub fn setShouldClose(self: *Surface) void {
         _ = self;
     }
 
-    pub fn shouldClose(self: *const Window) bool {
+    pub fn shouldClose(self: *const Surface) bool {
         _ = self;
         return false;
     }
 
-    pub fn getCursorPos(self: *const Window) !apprt.CursorPos {
+    pub fn getCursorPos(self: *const Surface) !apprt.CursorPos {
         return self.cursor_pos;
     }
 
-    pub fn refresh(self: *Window) void {
-        self.core_win.refreshCallback() catch |err| {
+    pub fn refresh(self: *Surface) void {
+        self.core_surface.refreshCallback() catch |err| {
             log.err("error in refresh callback err={}", .{err});
             return;
         };
     }
 
-    pub fn updateContentScale(self: *Window, x: f64, y: f64) void {
+    pub fn updateContentScale(self: *Surface, x: f64, y: f64) void {
         self.content_scale = .{
             .x = @floatCast(f32, x),
             .y = @floatCast(f32, y),
         };
     }
 
-    pub fn updateSize(self: *Window, width: u32, height: u32) void {
+    pub fn updateSize(self: *Surface, width: u32, height: u32) void {
         self.size = .{
             .width = width,
             .height = height,
         };
 
         // Call the primary callback.
-        self.core_win.sizeCallback(self.size) catch |err| {
+        self.core_surface.sizeCallback(self.size) catch |err| {
             log.err("error in size callback err={}", .{err});
             return;
         };
     }
 
     pub fn mouseButtonCallback(
-        self: *const Window,
+        self: *Surface,
         action: input.MouseButtonState,
         button: input.MouseButton,
         mods: input.Mods,
     ) void {
-        self.core_win.mouseButtonCallback(action, button, mods) catch |err| {
+        self.core_surface.mouseButtonCallback(action, button, mods) catch |err| {
             log.err("error in mouse button callback err={}", .{err});
             return;
         };
     }
 
-    pub fn scrollCallback(self: *const Window, xoff: f64, yoff: f64) void {
-        self.core_win.scrollCallback(xoff, yoff) catch |err| {
+    pub fn scrollCallback(self: *Surface, xoff: f64, yoff: f64) void {
+        self.core_surface.scrollCallback(xoff, yoff) catch |err| {
             log.err("error in scroll callback err={}", .{err});
             return;
         };
     }
 
-    pub fn cursorPosCallback(self: *Window, x: f64, y: f64) void {
+    pub fn cursorPosCallback(self: *Surface, x: f64, y: f64) void {
         // Convert our unscaled x/y to scaled.
-        self.cursor_pos = self.core_win.window.cursorPosToPixels(.{
+        self.cursor_pos = self.cursorPosToPixels(.{
             .x = @floatCast(f32, x),
             .y = @floatCast(f32, y),
         }) catch |err| {
@@ -206,35 +250,35 @@ pub const Window = struct {
             return;
         };
 
-        self.core_win.cursorPosCallback(self.cursor_pos) catch |err| {
+        self.core_surface.cursorPosCallback(self.cursor_pos) catch |err| {
             log.err("error in cursor pos callback err={}", .{err});
             return;
         };
     }
 
     pub fn keyCallback(
-        self: *const Window,
+        self: *Surface,
         action: input.Action,
         key: input.Key,
         mods: input.Mods,
     ) void {
         // log.warn("key action={} key={} mods={}", .{ action, key, mods });
-        self.core_win.keyCallback(action, key, mods) catch |err| {
+        self.core_surface.keyCallback(action, key, mods) catch |err| {
             log.err("error in key callback err={}", .{err});
             return;
         };
     }
 
-    pub fn charCallback(self: *const Window, cp_: u32) void {
+    pub fn charCallback(self: *Surface, cp_: u32) void {
         const cp = std.math.cast(u21, cp_) orelse return;
-        self.core_win.charCallback(cp) catch |err| {
+        self.core_surface.charCallback(cp) catch |err| {
             log.err("error in char callback err={}", .{err});
             return;
         };
     }
 
-    pub fn focusCallback(self: *const Window, focused: bool) void {
-        self.core_win.focusCallback(focused) catch |err| {
+    pub fn focusCallback(self: *Surface, focused: bool) void {
+        self.core_surface.focusCallback(focused) catch |err| {
             log.err("error in focus callback err={}", .{err});
             return;
         };
@@ -242,8 +286,157 @@ pub const Window = struct {
 
     /// The cursor position from the host directly is in screen coordinates but
     /// all our interface works in pixels.
-    fn cursorPosToPixels(self: *const Window, pos: apprt.CursorPos) !apprt.CursorPos {
+    fn cursorPosToPixels(self: *const Surface, pos: apprt.CursorPos) !apprt.CursorPos {
         const scale = try self.getContentScale();
         return .{ .x = pos.x * scale.x, .y = pos.y * scale.y };
     }
 };
+
+// C API
+pub const CAPI = struct {
+    const global = &@import("../main.zig").state;
+    const Config = @import("../config.zig").Config;
+
+    /// Create a new app.
+    export fn ghostty_app_new(
+        opts: *const apprt.runtime.App.Options,
+        config: *const Config,
+    ) ?*App {
+        return app_new_(opts, config) catch |err| {
+            log.err("error initializing app err={}", .{err});
+            return null;
+        };
+    }
+
+    fn app_new_(
+        opts: *const apprt.runtime.App.Options,
+        config: *const Config,
+    ) !*App {
+        var core_app = try CoreApp.create(global.alloc, config);
+        errdefer core_app.destroy();
+
+        // Create our runtime app
+        var app = try global.alloc.create(App);
+        errdefer global.alloc.destroy(app);
+        app.* = try App.init(core_app, opts.*);
+        errdefer app.terminate();
+
+        return app;
+    }
+
+    /// Tick the event loop. This should be called whenever the "wakeup"
+    /// callback is invoked for the runtime.
+    export fn ghostty_app_tick(v: *App) void {
+        _ = v.core_app.tick(v) catch |err| {
+            log.err("error app tick err={}", .{err});
+        };
+    }
+
+    /// Return the userdata associated with the app.
+    export fn ghostty_app_userdata(v: *App) ?*anyopaque {
+        return v.opts.userdata;
+    }
+
+    export fn ghostty_app_free(v: *App) void {
+        const core_app = v.core_app;
+        v.terminate();
+        global.alloc.destroy(v);
+        core_app.destroy();
+    }
+
+    /// Create a new surface as part of an app.
+    export fn ghostty_surface_new(
+        app: *App,
+        opts: *const apprt.Surface.Options,
+    ) ?*Surface {
+        return surface_new_(app, opts) catch |err| {
+            log.err("error initializing surface err={}", .{err});
+            return null;
+        };
+    }
+
+    fn surface_new_(
+        app: *App,
+        opts: *const apprt.Surface.Options,
+    ) !*Surface {
+        return try app.newSurface(opts.*);
+    }
+
+    export fn ghostty_surface_free(ptr: *Surface) void {
+        ptr.app.closeSurface(ptr);
+    }
+
+    /// Returns the app associated with a surface.
+    export fn ghostty_surface_app(surface: *Surface) *App {
+        return surface.app;
+    }
+
+    /// Tell the surface that it needs to schedule a render
+    export fn ghostty_surface_refresh(surface: *Surface) void {
+        surface.refresh();
+    }
+
+    /// Update the size of a surface. This will trigger resize notifications
+    /// to the pty and the renderer.
+    export fn ghostty_surface_set_size(surface: *Surface, w: u32, h: u32) void {
+        surface.updateSize(w, h);
+    }
+
+    /// Update the content scale of the surface.
+    export fn ghostty_surface_set_content_scale(surface: *Surface, x: f64, y: f64) void {
+        surface.updateContentScale(x, y);
+    }
+
+    /// Update the focused state of a surface.
+    export fn ghostty_surface_set_focus(surface: *Surface, focused: bool) void {
+        surface.focusCallback(focused);
+    }
+
+    /// Tell the surface that it needs to schedule a render
+    export fn ghostty_surface_key(
+        surface: *Surface,
+        action: input.Action,
+        key: input.Key,
+        mods: c_int,
+    ) void {
+        surface.keyCallback(
+            action,
+            key,
+            @bitCast(input.Mods, @truncate(u8, @bitCast(c_uint, mods))),
+        );
+    }
+
+    /// Tell the surface that it needs to schedule a render
+    export fn ghostty_surface_char(surface: *Surface, codepoint: u32) void {
+        surface.charCallback(codepoint);
+    }
+
+    /// Tell the surface that it needs to schedule a render
+    export fn ghostty_surface_mouse_button(
+        surface: *Surface,
+        action: input.MouseButtonState,
+        button: input.MouseButton,
+        mods: c_int,
+    ) void {
+        surface.mouseButtonCallback(
+            action,
+            button,
+            @bitCast(input.Mods, @truncate(u8, @bitCast(c_uint, mods))),
+        );
+    }
+
+    /// Update the mouse position within the view.
+    export fn ghostty_surface_mouse_pos(surface: *Surface, x: f64, y: f64) void {
+        surface.cursorPosCallback(x, y);
+    }
+
+    export fn ghostty_surface_mouse_scroll(surface: *Surface, x: f64, y: f64) void {
+        surface.scrollCallback(x, y);
+    }
+
+    export fn ghostty_surface_ime_point(surface: *Surface, x: *f64, y: *f64) void {
+        const pos = surface.core_surface.imePoint();
+        x.* = pos.x;
+        y.* = pos.y;
+    }
+};
diff --git a/src/apprt/glfw.zig b/src/apprt/glfw.zig
index 1e03f30e9..dbdb925d3 100644
--- a/src/apprt/glfw.zig
+++ b/src/apprt/glfw.zig
@@ -5,10 +5,12 @@
 
 const std = @import("std");
 const builtin = @import("builtin");
+const build_config = @import("../build_config.zig");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const trace = @import("tracy").trace;
 const glfw = @import("glfw");
+const macos = @import("macos");
 const objc = @import("objc");
 const input = @import("../input.zig");
 const internal_os = @import("../os/main.zig");
@@ -16,7 +18,7 @@ const renderer = @import("../renderer.zig");
 const Renderer = renderer.Renderer;
 const apprt = @import("../apprt.zig");
 const CoreApp = @import("../App.zig");
-const CoreWindow = @import("../Window.zig");
+const CoreSurface = @import("../Surface.zig");
 
 // Get native API access on certain platforms so we can do more customization.
 const glfwNative = glfw.Native(.{
@@ -26,11 +28,25 @@ const glfwNative = glfw.Native(.{
 const log = std.log.scoped(.glfw);
 
 pub const App = struct {
+    app: *CoreApp,
+
+    /// Mac-specific state.
+    darwin: if (Darwin.enabled) Darwin else void,
+
     pub const Options = struct {};
 
-    pub fn init(_: Options) !App {
+    pub fn init(core_app: *CoreApp, _: Options) !App {
         if (!glfw.init(.{})) return error.GlfwInitFailed;
-        return .{};
+        glfw.setErrorCallback(glfwErrorCallback);
+
+        // Mac-specific state. For example, on Mac we enable window tabbing.
+        var darwin = if (Darwin.enabled) try Darwin.init() else {};
+        errdefer if (Darwin.enabled) darwin.deinit();
+
+        return .{
+            .app = core_app,
+            .darwin = darwin,
+        };
     }
 
     pub fn terminate(self: App) void {
@@ -38,31 +54,170 @@ pub const App = struct {
         glfw.terminate();
     }
 
+    /// Run the event loop. This doesn't return until the app exits.
+    pub fn run(self: *App) !void {
+        while (true) {
+            // Wait for any events from the app event loop. wakeup will post
+            // an empty event so that this will return.
+            glfw.waitEvents();
+
+            // Tick the terminal app
+            const should_quit = try self.app.tick(self);
+            if (should_quit) return;
+        }
+    }
+
     /// Wakeup the event loop. This should be able to be called from any thread.
-    pub fn wakeup(self: App) !void {
+    pub fn wakeup(self: *const App) void {
         _ = self;
         glfw.postEmptyEvent();
     }
 
-    /// Wait for events in the event loop to process.
-    pub fn wait(self: App) !void {
-        _ = self;
-        glfw.waitEvents();
+    /// Create a new window for the app.
+    pub fn newWindow(self: *App, parent_: ?*CoreSurface) !void {
+        _ = try self.newSurface(parent_);
     }
+
+    /// Create a new tab in the parent surface.
+    pub fn newTab(self: *App, parent: *CoreSurface) !void {
+        if (!Darwin.enabled) {
+            log.warn("tabbing is not supported on this platform", .{});
+            return;
+        }
+
+        // Create the new window
+        const window = try self.newSurface(parent);
+
+        // Add the new window the parent window
+        const parent_win = glfwNative.getCocoaWindow(parent.rt_surface.window).?;
+        const other_win = glfwNative.getCocoaWindow(window.window).?;
+        const NSWindowOrderingMode = enum(isize) { below = -1, out = 0, above = 1 };
+        const nswindow = objc.Object.fromId(parent_win);
+        nswindow.msgSend(void, objc.sel("addTabbedWindow:ordered:"), .{
+            objc.Object.fromId(other_win),
+            NSWindowOrderingMode.above,
+        });
+
+        // Adding a new tab can cause the tab bar to appear which changes
+        // our viewport size. We need to call the size callback in order to
+        // update values. For example, we need this to set the proper mouse selection
+        // point in the grid.
+        const size = parent.rt_surface.getSize() catch |err| {
+            log.err("error querying window size for size callback on new tab err={}", .{err});
+            return;
+        };
+        parent.sizeCallback(size) catch |err| {
+            log.err("error in size callback from new tab err={}", .{err});
+            return;
+        };
+    }
+
+    fn newSurface(self: *App, parent_: ?*CoreSurface) !*Surface {
+        // Grab a surface allocation because we're going to need it.
+        var surface = try self.app.alloc.create(Surface);
+        errdefer self.app.alloc.destroy(surface);
+
+        // Create the surface -- because windows are surfaces for glfw.
+        try surface.init(self);
+        errdefer surface.deinit();
+
+        // If we have a parent, inherit some properties
+        if (self.app.config.@"window-inherit-font-size") {
+            if (parent_) |parent| {
+                surface.core_surface.setFontSize(parent.font_size);
+            }
+        }
+
+        return surface;
+    }
+
+    /// Close the given surface.
+    pub fn closeSurface(self: *App, surface: *Surface) void {
+        surface.deinit();
+        self.app.alloc.destroy(surface);
+    }
+
+    pub fn redrawSurface(self: *App, surface: *Surface) void {
+        _ = self;
+        _ = surface;
+
+        @panic("This should never be called for GLFW.");
+    }
+
+    fn glfwErrorCallback(code: glfw.ErrorCode, desc: [:0]const u8) void {
+        std.log.warn("glfw error={} message={s}", .{ code, desc });
+
+        // Workaround for: https://github.com/ocornut/imgui/issues/5908
+        // If we get an invalid value with "scancode" in the message we assume
+        // it is from the glfw key callback that imgui sets and we clear the
+        // error so that our future code doesn't crash.
+        if (code == glfw.ErrorCode.InvalidValue and
+            std.mem.indexOf(u8, desc, "scancode") != null)
+        {
+            _ = glfw.getError();
+        }
+    }
+
+    /// Mac-specific settings. This is only enabled when the target is
+    /// Mac and the artifact is a standalone exe. We don't target libs because
+    /// the embedded API doesn't do windowing.
+    const Darwin = struct {
+        const enabled = builtin.target.isDarwin() and build_config.artifact == .exe;
+
+        tabbing_id: *macos.foundation.String,
+
+        pub fn init() !Darwin {
+            const NSWindow = objc.Class.getClass("NSWindow").?;
+            NSWindow.msgSend(void, objc.sel("setAllowsAutomaticWindowTabbing:"), .{true});
+
+            // Our tabbing ID allows all of our windows to group together
+            const tabbing_id = try macos.foundation.String.createWithBytes(
+                "com.mitchellh.ghostty.window",
+                .utf8,
+                false,
+            );
+            errdefer tabbing_id.release();
+
+            // Setup our Mac settings
+            return .{ .tabbing_id = tabbing_id };
+        }
+
+        pub fn deinit(self: *Darwin) void {
+            self.tabbing_id.release();
+            self.* = undefined;
+        }
+    };
 };
 
-pub const Window = struct {
+/// Surface represents the drawable surface for glfw. In glfw, a surface
+/// is always a window because that is the only abstraction that glfw exposes.
+///
+/// This means that there is no way for the glfw runtime to support tabs,
+/// splits, etc. without considerable effort. In fact, on Darwin, we do
+/// support tabs because the minimal tabbing interface is a window abstraction,
+/// but this is a bit of a hack. The native Swift runtime should be used instead
+/// which uses real native tabbing.
+///
+/// Other runtimes a surface usually represents the equivalent of a "view"
+/// or "widget" level granularity.
+pub const Surface = struct {
     /// The glfw window handle
     window: glfw.Window,
 
     /// The glfw mouse cursor handle.
     cursor: glfw.Cursor,
 
+    /// The app we're part of
+    app: *App,
+
+    /// A core surface
+    core_surface: CoreSurface,
+
     pub const Options = struct {};
 
-    pub fn init(app: *const CoreApp, core_win: *CoreWindow, opts: Options) !Window {
-        _ = opts;
-
+    /// Initialize the surface into the given self pointer. This gives a
+    /// stable pointer to the destination that can be used for callbacks.
+    pub fn init(self: *Surface, app: *App) !void {
         // Create our window
         const win = glfw.Window.create(
             640,
@@ -74,9 +229,9 @@ pub const Window = struct {
         ) orelse return glfw.mustGetErrorCode();
         errdefer win.destroy();
 
+        // Get our physical DPI - debug only because we don't have a use for
+        // this but the logging of it may be useful
         if (builtin.mode == .Debug) {
-            // Get our physical DPI - debug only because we don't have a use for
-            // this but the logging of it may be useful
             const monitor = win.getMonitor() orelse monitor: {
                 log.warn("window had null monitor, getting primary monitor", .{});
                 break :monitor glfw.Monitor.getPrimary().?;
@@ -91,8 +246,8 @@ pub const Window = struct {
             });
         }
 
-        // On Mac, enable tabbing
-        if (comptime builtin.target.isDarwin()) {
+        // On Mac, enable window tabbing
+        if (App.Darwin.enabled) {
             const NSWindowTabbingMode = enum(usize) { automatic = 0, preferred = 1, disallowed = 2 };
             const nswindow = objc.Object.fromId(glfwNative.getCocoaWindow(win).?);
 
@@ -115,7 +270,7 @@ pub const Window = struct {
         }
 
         // Set our callbacks
-        win.setUserPointer(core_win);
+        win.setUserPointer(&self.core_surface);
         win.setSizeCallback(sizeCallback);
         win.setCharCallback(charCallback);
         win.setKeyCallback(keyCallback);
@@ -126,15 +281,37 @@ pub const Window = struct {
         win.setMouseButtonCallback(mouseButtonCallback);
 
         // Build our result
-        return Window{
+        self.* = .{
+            .app = app,
             .window = win,
             .cursor = cursor,
+            .core_surface = undefined,
         };
+        errdefer self.* = undefined;
+
+        // Add ourselves to the list of surfaces on the app.
+        try app.app.addSurface(self);
+        errdefer app.app.deleteSurface(self);
+
+        // Initialize our surface now that we have the stable pointer.
+        try self.core_surface.init(
+            app.app.alloc,
+            app.app.config,
+            .{ .rt_app = app, .mailbox = &app.app.mailbox },
+            self,
+        );
+        errdefer self.core_surface.deinit();
     }
 
-    pub fn deinit(self: *Window) void {
-        var tabgroup_opt: if (builtin.target.isDarwin()) ?objc.Object else void = undefined;
-        if (comptime builtin.target.isDarwin()) {
+    pub fn deinit(self: *Surface) void {
+        // Remove ourselves from the list of known surfaces in the app.
+        self.app.app.deleteSurface(self);
+
+        // Clean up our core surface so that all the rendering and IO stop.
+        self.core_surface.deinit();
+
+        var tabgroup_opt: if (App.Darwin.enabled) ?objc.Object else void = undefined;
+        if (App.Darwin.enabled) {
             const nswindow = objc.Object.fromId(glfwNative.getCocoaWindow(self.window).?);
             const tabgroup = nswindow.getProperty(objc.Object, "tabGroup");
 
@@ -171,7 +348,7 @@ pub const Window = struct {
 
         // If we have a tabgroup set, we want to manually focus the next window.
         // We should NOT have to do this usually, see the comments above.
-        if (comptime builtin.target.isDarwin()) {
+        if (App.Darwin.enabled) {
             if (tabgroup_opt) |tabgroup| {
                 const selected = tabgroup.getProperty(objc.Object, "selectedWindow");
                 selected.msgSend(void, objc.sel("makeKeyWindow"), .{});
@@ -183,7 +360,7 @@ pub const Window = struct {
     /// Note: this interface is not good, we should redo it if we plan
     /// to use this more. i.e. you can't set max width but no max height,
     /// or no mins.
-    pub fn setSizeLimits(self: *Window, min: apprt.WindowSize, max_: ?apprt.WindowSize) !void {
+    pub fn setSizeLimits(self: *Surface, min: apprt.SurfaceSize, max_: ?apprt.SurfaceSize) !void {
         self.window.setSizeLimits(.{
             .width = min.width,
             .height = min.height,
@@ -197,7 +374,7 @@ pub const Window = struct {
     }
 
     /// Returns the content scale for the created window.
-    pub fn getContentScale(self: *const Window) !apprt.ContentScale {
+    pub fn getContentScale(self: *const Surface) !apprt.ContentScale {
         const scale = self.window.getContentScale();
         return apprt.ContentScale{ .x = scale.x_scale, .y = scale.y_scale };
     }
@@ -205,14 +382,14 @@ pub const Window = struct {
     /// Returns the size of the window in pixels. The pixel size may
     /// not match screen coordinate size but we should be able to convert
     /// back and forth using getContentScale.
-    pub fn getSize(self: *const Window) !apprt.WindowSize {
+    pub fn getSize(self: *const Surface) !apprt.SurfaceSize {
         const size = self.window.getFramebufferSize();
-        return apprt.WindowSize{ .width = size.width, .height = size.height };
+        return apprt.SurfaceSize{ .width = size.width, .height = size.height };
     }
 
     /// Returns the cursor position in scaled pixels relative to the
     /// upper-left of the window.
-    pub fn getCursorPos(self: *const Window) !apprt.CursorPos {
+    pub fn getCursorPos(self: *const Surface) !apprt.CursorPos {
         const unscaled_pos = self.window.getCursorPos();
         const pos = try self.cursorPosToPixels(unscaled_pos);
         return apprt.CursorPos{
@@ -223,37 +400,37 @@ pub const Window = struct {
 
     /// Set the flag that notes this window should be closed for the next
     /// iteration of the event loop.
-    pub fn setShouldClose(self: *Window) void {
+    pub fn setShouldClose(self: *Surface) void {
         self.window.setShouldClose(true);
     }
 
     /// Returns true if the window is flagged to close.
-    pub fn shouldClose(self: *const Window) bool {
+    pub fn shouldClose(self: *const Surface) bool {
         return self.window.shouldClose();
     }
 
     /// Set the title of the window.
-    pub fn setTitle(self: *Window, slice: [:0]const u8) !void {
+    pub fn setTitle(self: *Surface, slice: [:0]const u8) !void {
         self.window.setTitle(slice.ptr);
     }
 
     /// Read the clipboard. The windowing system is responsible for allocating
     /// a buffer as necessary. This should be a stable pointer until the next
     /// time getClipboardString is called.
-    pub fn getClipboardString(self: *const Window) ![:0]const u8 {
+    pub fn getClipboardString(self: *const Surface) ![:0]const u8 {
         _ = self;
         return glfw.getClipboardString() orelse return glfw.mustGetErrorCode();
     }
 
     /// Set the clipboard.
-    pub fn setClipboardString(self: *const Window, val: [:0]const u8) !void {
+    pub fn setClipboardString(self: *const Surface, val: [:0]const u8) !void {
         _ = self;
         glfw.setClipboardString(val);
     }
 
     /// The cursor position from glfw directly is in screen coordinates but
     /// all our interface works in pixels.
-    fn cursorPosToPixels(self: *const Window, pos: glfw.Window.CursorPos) !glfw.Window.CursorPos {
+    fn cursorPosToPixels(self: *const Surface, pos: glfw.Window.CursorPos) !glfw.Window.CursorPos {
         // The cursor position is in screen coordinates but we
         // want it in pixels. we need to get both the size of the
         // window in both to get the ratio to make the conversion.
@@ -280,8 +457,8 @@ pub const Window = struct {
         // Get the size. We are given a width/height but this is in screen
         // coordinates and we want raw pixels. The core window uses the content
         // scale to scale appropriately.
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
-        const size = core_win.window.getSize() catch |err| {
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
+        const size = core_win.rt_surface.getSize() catch |err| {
             log.err("error querying window size for size callback err={}", .{err});
             return;
         };
@@ -297,7 +474,7 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
         core_win.charCallback(codepoint) catch |err| {
             log.err("error in char callback err={}", .{err});
             return;
@@ -449,7 +626,7 @@ pub const Window = struct {
             => .invalid,
         };
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
         core_win.keyCallback(action, key, mods) catch |err| {
             log.err("error in key callback err={}", .{err});
             return;
@@ -460,7 +637,7 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
         core_win.focusCallback(focused) catch |err| {
             log.err("error in focus callback err={}", .{err});
             return;
@@ -471,7 +648,7 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
         core_win.refreshCallback() catch |err| {
             log.err("error in refresh callback err={}", .{err});
             return;
@@ -482,7 +659,7 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
         core_win.scrollCallback(xoff, yoff) catch |err| {
             log.err("error in scroll callback err={}", .{err});
             return;
@@ -497,10 +674,10 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
 
         // Convert our unscaled x/y to scaled.
-        const pos = core_win.window.cursorPosToPixels(.{
+        const pos = core_win.rt_surface.cursorPosToPixels(.{
             .xpos = unscaled_xpos,
             .ypos = unscaled_ypos,
         }) catch |err| {
@@ -529,7 +706,7 @@ pub const Window = struct {
         const tracy = trace(@src());
         defer tracy.end();
 
-        const core_win = window.getUserPointer(CoreWindow) orelse return;
+        const core_win = window.getUserPointer(CoreSurface) orelse return;
 
         // Convert glfw button to input button
         const mods = @bitCast(input.Mods, glfw_mods);
diff --git a/src/apprt/gtk.zig b/src/apprt/gtk.zig
new file mode 100644
index 000000000..530dbbe8c
--- /dev/null
+++ b/src/apprt/gtk.zig
@@ -0,0 +1,801 @@
+//! Application runtime that uses GTK4.
+
+const std = @import("std");
+const builtin = @import("builtin");
+const assert = std.debug.assert;
+const Allocator = std.mem.Allocator;
+const glfw = @import("glfw");
+const apprt = @import("../apprt.zig");
+const input = @import("../input.zig");
+const CoreApp = @import("../App.zig");
+const CoreSurface = @import("../Surface.zig");
+
+pub const c = @cImport({
+    @cInclude("gtk/gtk.h");
+});
+
+const log = std.log.scoped(.gtk);
+
+/// App is the entrypoint for the application. This is called after all
+/// of the runtime-agnostic initialization is complete and we're ready
+/// to start.
+///
+/// There is only ever one App instance per process. This is because most
+/// application frameworks also have this restriction so it simplifies
+/// the assumptions.
+pub const App = struct {
+    pub const Options = struct {
+        /// GTK app ID
+        id: [:0]const u8 = "com.mitchellh.ghostty",
+    };
+
+    core_app: *CoreApp,
+
+    app: *c.GtkApplication,
+    ctx: *c.GMainContext,
+
+    cursor_default: *c.GdkCursor,
+    cursor_ibeam: *c.GdkCursor,
+
+    pub fn init(core_app: *CoreApp, opts: Options) !App {
+        // This is super weird, but we still use GLFW with GTK only so that
+        // we can tap into their folklore logic to get screen DPI. If we can
+        // figure out a reliable way to determine this ourselves, we can get
+        // rid of this dep.
+        if (!glfw.init(.{})) return error.GlfwInitFailed;
+
+        // Create our GTK Application which encapsulates our process.
+        const app = @ptrCast(?*c.GtkApplication, c.gtk_application_new(
+            opts.id.ptr,
+            c.G_APPLICATION_DEFAULT_FLAGS,
+        )) orelse return error.GtkInitFailed;
+        errdefer c.g_object_unref(app);
+        _ = c.g_signal_connect_data(
+            app,
+            "activate",
+            c.G_CALLBACK(&activate),
+            null,
+            null,
+            c.G_CONNECT_DEFAULT,
+        );
+
+        // We don't use g_application_run, we want to manually control the
+        // loop so we have to do the same things the run function does:
+        // https://github.com/GNOME/glib/blob/a8e8b742e7926e33eb635a8edceac74cf239d6ed/gio/gapplication.c#L2533
+        const ctx = c.g_main_context_default() orelse return error.GtkContextFailed;
+        if (c.g_main_context_acquire(ctx) == 0) return error.GtkContextAcquireFailed;
+        errdefer c.g_main_context_release(ctx);
+
+        const gapp = @ptrCast(*c.GApplication, app);
+        var err_: ?*c.GError = null;
+        if (c.g_application_register(
+            gapp,
+            null,
+            @ptrCast([*c][*c]c.GError, &err_),
+        ) == 0) {
+            if (err_) |err| {
+                log.warn("error registering application: {s}", .{err.message});
+                c.g_error_free(err);
+            }
+            return error.GtkApplicationRegisterFailed;
+        }
+
+        // This just calls the "activate" signal but its part of the normal
+        // startup routine so we just call it:
+        // https://gitlab.gnome.org/GNOME/glib/-/blob/bd2ccc2f69ecfd78ca3f34ab59e42e2b462bad65/gio/gapplication.c#L2302
+        c.g_application_activate(gapp);
+
+        // Get our cursors
+        const cursor_default = c.gdk_cursor_new_from_name("default", null).?;
+        errdefer c.g_object_unref(cursor_default);
+        const cursor_ibeam = c.gdk_cursor_new_from_name("text", cursor_default).?;
+        errdefer c.g_object_unref(cursor_ibeam);
+
+        return .{
+            .core_app = core_app,
+            .app = app,
+            .ctx = ctx,
+            .cursor_default = cursor_default,
+            .cursor_ibeam = cursor_ibeam,
+        };
+    }
+
+    // Terminate the application. The application will not be restarted after
+    // this so all global state can be cleaned up.
+    pub fn terminate(self: App) void {
+        c.g_settings_sync();
+        while (c.g_main_context_iteration(self.ctx, 0) != 0) {}
+        c.g_main_context_release(self.ctx);
+        c.g_object_unref(self.app);
+
+        c.g_object_unref(self.cursor_ibeam);
+        c.g_object_unref(self.cursor_default);
+
+        glfw.terminate();
+    }
+
+    pub fn wakeup(self: App) void {
+        _ = self;
+        c.g_main_context_wakeup(null);
+    }
+
+    /// Run the event loop. This doesn't return until the app exits.
+    pub fn run(self: *App) !void {
+        while (true) {
+            _ = c.g_main_context_iteration(self.ctx, 1);
+
+            // Tick the terminal app
+            const should_quit = try self.core_app.tick(self);
+            if (should_quit) return;
+        }
+    }
+
+    /// Close the given surface.
+    pub fn closeSurface(self: *App, surface: *Surface) void {
+        _ = self;
+        _ = surface;
+
+        // This shouldn't be called because we should be working within
+        // the GTK lifecycle and we can't just deallocate surfaces here.
+        @panic("This should not be called with GTK.");
+    }
+
+    pub fn redrawSurface(self: *App, surface: *Surface) void {
+        _ = self;
+        surface.invalidate();
+    }
+
+    pub fn newWindow(self: *App, parent_: ?*CoreSurface) !void {
+        _ = parent_;
+
+        // Grab a surface allocation we'll need it later.
+        var surface = try self.core_app.alloc.create(Surface);
+        errdefer self.core_app.alloc.destroy(surface);
+
+        const window = c.gtk_application_window_new(self.app);
+        const gtk_window = @ptrCast(*c.GtkWindow, window);
+        c.gtk_window_set_title(gtk_window, "Ghostty");
+        c.gtk_window_set_default_size(gtk_window, 200, 200);
+        c.gtk_widget_show(window);
+
+        // Initialize the GtkGLArea and attach it to our surface.
+        // The surface starts in the "unrealized" state because we have to
+        // wait for the "realize" callback from GTK to know that the OpenGL
+        // context is ready. See Surface docs for more info.
+        const gl_area = c.gtk_gl_area_new();
+        try surface.init(self, .{
+            .gl_area = @ptrCast(*c.GtkGLArea, gl_area),
+        });
+        errdefer surface.deinit();
+        c.gtk_window_set_child(gtk_window, gl_area);
+
+        // We need to grab focus after it is added to the window. When
+        // creating a window we want to always focus on the widget.
+        const widget = @ptrCast(*c.GtkWidget, gl_area);
+        _ = c.gtk_widget_grab_focus(widget);
+    }
+
+    fn activate(app: *c.GtkApplication, ud: ?*anyopaque) callconv(.C) void {
+        _ = app;
+        _ = ud;
+
+        // We purposely don't do anything on activation right now. We have
+        // this callback because if we don't then GTK emits a warning to
+        // stderr that we don't want. We emit a debug log just so that we know
+        // we reached this point.
+        log.debug("application activated", .{});
+    }
+};
+
+pub const Surface = struct {
+    /// This is detected by the OpenGL renderer to move to a single-threaded
+    /// draw operation. This basically puts locks around our draw path.
+    pub const opengl_single_threaded_draw = true;
+
+    pub const Options = struct {
+        gl_area: *c.GtkGLArea,
+    };
+
+    /// Whether the surface has been realized or not yet. When a surface is
+    /// "realized" it means that the OpenGL context is ready and the core
+    /// surface has been initialized.
+    realized: bool = false,
+
+    /// The app we're part of
+    app: *App,
+
+    /// Our GTK area
+    gl_area: *c.GtkGLArea,
+
+    /// The core surface backing this surface
+    core_surface: CoreSurface,
+
+    /// Cached metrics about the surface from GTK callbacks.
+    size: apprt.SurfaceSize,
+    cursor_pos: apprt.CursorPos,
+    clipboard: c.GValue,
+
+    pub fn init(self: *Surface, app: *App, opts: Options) !void {
+        const widget = @ptrCast(*c.GtkWidget, opts.gl_area);
+        c.gtk_gl_area_set_required_version(opts.gl_area, 3, 3);
+        c.gtk_gl_area_set_has_stencil_buffer(opts.gl_area, 0);
+        c.gtk_gl_area_set_has_depth_buffer(opts.gl_area, 0);
+        c.gtk_gl_area_set_use_es(opts.gl_area, 0);
+
+        // Key event controller will tell us about raw keypress events.
+        const ec_key = c.gtk_event_controller_key_new();
+        errdefer c.g_object_unref(ec_key);
+        c.gtk_widget_add_controller(widget, ec_key);
+        errdefer c.gtk_widget_remove_controller(widget, ec_key);
+
+        // Focus controller will tell us about focus enter/exit events
+        const ec_focus = c.gtk_event_controller_focus_new();
+        errdefer c.g_object_unref(ec_focus);
+        c.gtk_widget_add_controller(widget, ec_focus);
+        errdefer c.gtk_widget_remove_controller(widget, ec_focus);
+
+        // Tell the key controller that we're interested in getting a full
+        // input method so raw characters/strings are given too.
+        const im_context = c.gtk_im_multicontext_new();
+        errdefer c.g_object_unref(im_context);
+        c.gtk_event_controller_key_set_im_context(
+            @ptrCast(*c.GtkEventControllerKey, ec_key),
+            im_context,
+        );
+
+        // Create a second key controller so we can receive the raw
+        // key-press events BEFORE the input method gets them.
+        const ec_key_press = c.gtk_event_controller_key_new();
+        errdefer c.g_object_unref(ec_key_press);
+        c.gtk_widget_add_controller(widget, ec_key_press);
+        errdefer c.gtk_widget_remove_controller(widget, ec_key_press);
+
+        // Clicks
+        const gesture_click = c.gtk_gesture_click_new();
+        errdefer c.g_object_unref(gesture_click);
+        c.gtk_gesture_single_set_button(@ptrCast(
+            *c.GtkGestureSingle,
+            gesture_click,
+        ), 0);
+        c.gtk_widget_add_controller(widget, @ptrCast(
+            *c.GtkEventController,
+            gesture_click,
+        ));
+
+        // Mouse movement
+        const ec_motion = c.gtk_event_controller_motion_new();
+        errdefer c.g_object_unref(ec_motion);
+        c.gtk_widget_add_controller(widget, ec_motion);
+
+        // Scroll events
+        const ec_scroll = c.gtk_event_controller_scroll_new(
+            c.GTK_EVENT_CONTROLLER_SCROLL_BOTH_AXES |
+                c.GTK_EVENT_CONTROLLER_SCROLL_DISCRETE,
+        );
+        errdefer c.g_object_unref(ec_scroll);
+        c.gtk_widget_add_controller(widget, ec_scroll);
+
+        // The GL area has to be focusable so that it can receive events
+        c.gtk_widget_set_focusable(widget, 1);
+        c.gtk_widget_set_focus_on_click(widget, 1);
+
+        // When we're over the widget, set the cursor to the ibeam
+        c.gtk_widget_set_cursor(widget, app.cursor_ibeam);
+
+        // Build our result
+        self.* = .{
+            .app = app,
+            .gl_area = opts.gl_area,
+            .core_surface = undefined,
+            .size = .{ .width = 800, .height = 600 },
+            .cursor_pos = .{ .x = 0, .y = 0 },
+            .clipboard = std.mem.zeroes(c.GValue),
+        };
+        errdefer self.* = undefined;
+
+        // GL events
+        _ = c.g_signal_connect_data(opts.gl_area, "realize", c.G_CALLBACK(&gtkRealize), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(opts.gl_area, "destroy", c.G_CALLBACK(&gtkDestroy), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(opts.gl_area, "render", c.G_CALLBACK(&gtkRender), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(opts.gl_area, "resize", c.G_CALLBACK(&gtkResize), self, null, c.G_CONNECT_DEFAULT);
+
+        _ = c.g_signal_connect_data(ec_key_press, "key-pressed", c.G_CALLBACK(&gtkKeyPressed), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(ec_key_press, "key-released", c.G_CALLBACK(&gtkKeyReleased), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(ec_focus, "enter", c.G_CALLBACK(&gtkFocusEnter), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(ec_focus, "leave", c.G_CALLBACK(&gtkFocusLeave), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(im_context, "commit", c.G_CALLBACK(&gtkInputCommit), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(gesture_click, "pressed", c.G_CALLBACK(&gtkMouseDown), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(gesture_click, "released", c.G_CALLBACK(&gtkMouseUp), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(ec_motion, "motion", c.G_CALLBACK(&gtkMouseMotion), self, null, c.G_CONNECT_DEFAULT);
+        _ = c.g_signal_connect_data(ec_scroll, "scroll", c.G_CALLBACK(&gtkMouseScroll), self, null, c.G_CONNECT_DEFAULT);
+    }
+
+    fn realize(self: *Surface) !void {
+        // Add ourselves to the list of surfaces on the app.
+        try self.app.core_app.addSurface(self);
+        errdefer self.app.core_app.deleteSurface(self);
+
+        // Initialize our surface now that we have the stable pointer.
+        try self.core_surface.init(
+            self.app.core_app.alloc,
+            self.app.core_app.config,
+            .{ .rt_app = self.app, .mailbox = &self.app.core_app.mailbox },
+            self,
+        );
+        errdefer self.core_surface.deinit();
+
+        // Note we're realized
+        self.realized = true;
+    }
+
+    pub fn deinit(self: *Surface) void {
+        c.g_value_unset(&self.clipboard);
+
+        // We don't allocate anything if we aren't realized.
+        if (!self.realized) return;
+
+        // Remove ourselves from the list of known surfaces in the app.
+        self.app.core_app.deleteSurface(self);
+
+        // Clean up our core surface so that all the rendering and IO stop.
+        self.core_surface.deinit();
+        self.core_surface = undefined;
+    }
+
+    fn render(self: *Surface) !void {
+        try self.core_surface.renderer.draw();
+    }
+
+    /// Invalidate the surface so that it forces a redraw on the next tick.
+    fn invalidate(self: *Surface) void {
+        c.gtk_gl_area_queue_render(self.gl_area);
+    }
+
+    pub fn setShouldClose(self: *Surface) void {
+        _ = self;
+    }
+
+    pub fn shouldClose(self: *const Surface) bool {
+        _ = self;
+        return false;
+    }
+
+    pub fn getContentScale(self: *const Surface) !apprt.ContentScale {
+        _ = self;
+        const monitor = glfw.Monitor.getPrimary() orelse return error.NoMonitor;
+        const scale = monitor.getContentScale();
+        return apprt.ContentScale{ .x = scale.x_scale, .y = scale.y_scale };
+    }
+
+    pub fn getSize(self: *const Surface) !apprt.SurfaceSize {
+        return self.size;
+    }
+
+    pub fn setSizeLimits(self: *Surface, min: apprt.SurfaceSize, max_: ?apprt.SurfaceSize) !void {
+        _ = self;
+        _ = min;
+        _ = max_;
+    }
+
+    pub fn setTitle(self: *Surface, slice: [:0]const u8) !void {
+        const root = c.gtk_widget_get_root(@ptrCast(
+            *c.GtkWidget,
+            self.gl_area,
+        ));
+
+        // TODO: we need a way to check if the type is a window
+        _ = root;
+        _ = slice;
+    }
+
+    pub fn getClipboardString(self: *Surface) ![:0]const u8 {
+        const clipboard = c.gtk_widget_get_clipboard(@ptrCast(
+            *c.GtkWidget,
+            self.gl_area,
+        ));
+
+        const content = c.gdk_clipboard_get_content(clipboard) orelse {
+            // On my machine, this NEVER works, so we fallback to glfw's
+            // implementation...
+            log.debug("no GTK clipboard contents, falling back to glfw", .{});
+            return glfw.getClipboardString() orelse return glfw.mustGetErrorCode();
+        };
+
+        c.g_value_unset(&self.clipboard);
+        _ = c.g_value_init(&self.clipboard, c.G_TYPE_STRING);
+        if (c.gdk_content_provider_get_value(content, &self.clipboard, null) == 0) {
+            return "";
+        }
+
+        const ptr = c.g_value_get_string(&self.clipboard);
+        return std.mem.sliceTo(ptr, 0);
+    }
+
+    pub fn setClipboardString(self: *const Surface, val: [:0]const u8) !void {
+        const clipboard = c.gtk_widget_get_clipboard(@ptrCast(
+            *c.GtkWidget,
+            self.gl_area,
+        ));
+
+        c.gdk_clipboard_set_text(clipboard, val.ptr);
+    }
+
+    pub fn getCursorPos(self: *const Surface) !apprt.CursorPos {
+        return self.cursor_pos;
+    }
+
+    fn gtkRealize(area: *c.GtkGLArea, ud: ?*anyopaque) callconv(.C) void {
+        log.debug("gl surface realized", .{});
+
+        // We need to make the context current so we can call GL functions.
+        c.gtk_gl_area_make_current(area);
+        if (c.gtk_gl_area_get_error(area)) |err| {
+            log.err("surface failed to realize: {s}", .{err.*.message});
+            return;
+        }
+
+        // realize means that our OpenGL context is ready, so we can now
+        // initialize the core surface which will setup the renderer.
+        const self = userdataSelf(ud.?);
+        self.realize() catch |err| {
+            // TODO: we need to destroy the GL area here.
+            log.err("surface failed to realize: {}", .{err});
+            return;
+        };
+    }
+
+    /// render singal
+    fn gtkRender(area: *c.GtkGLArea, ctx: *c.GdkGLContext, ud: ?*anyopaque) callconv(.C) c.gboolean {
+        _ = area;
+        _ = ctx;
+
+        const self = userdataSelf(ud.?);
+        self.render() catch |err| {
+            log.err("surface failed to render: {}", .{err});
+            return 0;
+        };
+
+        return 1;
+    }
+
+    /// render singal
+    fn gtkResize(area: *c.GtkGLArea, width: c.gint, height: c.gint, ud: ?*anyopaque) callconv(.C) void {
+        _ = area;
+        log.debug("gl resize {} {}", .{ width, height });
+
+        const self = userdataSelf(ud.?);
+        self.size = .{
+            .width = @intCast(u32, width),
+            .height = @intCast(u32, height),
+        };
+
+        // Call the primary callback.
+        if (self.realized) {
+            self.core_surface.sizeCallback(self.size) catch |err| {
+                log.err("error in size callback err={}", .{err});
+                return;
+            };
+        }
+    }
+
+    /// "destroy" signal for surface
+    fn gtkDestroy(v: *c.GtkWidget, ud: ?*anyopaque) callconv(.C) void {
+        _ = v;
+        log.debug("gl destroy", .{});
+
+        const self = userdataSelf(ud.?);
+        const alloc = self.app.core_app.alloc;
+        self.deinit();
+        alloc.destroy(self);
+    }
+
+    fn gtkMouseDown(
+        gesture: *c.GtkGestureClick,
+        _: c.gint,
+        _: c.gdouble,
+        _: c.gdouble,
+        ud: ?*anyopaque,
+    ) callconv(.C) void {
+        const button = translateMouseButton(c.gtk_gesture_single_get_current_button(@ptrCast(
+            *c.GtkGestureSingle,
+            gesture,
+        )));
+
+        const self = userdataSelf(ud.?);
+        self.core_surface.mouseButtonCallback(.press, button, .{}) catch |err| {
+            log.err("error in key callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn gtkMouseUp(
+        gesture: *c.GtkGestureClick,
+        _: c.gint,
+        _: c.gdouble,
+        _: c.gdouble,
+        ud: ?*anyopaque,
+    ) callconv(.C) void {
+        const button = translateMouseButton(c.gtk_gesture_single_get_current_button(@ptrCast(
+            *c.GtkGestureSingle,
+            gesture,
+        )));
+
+        const self = userdataSelf(ud.?);
+        self.core_surface.mouseButtonCallback(.release, button, .{}) catch |err| {
+            log.err("error in key callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn gtkMouseMotion(
+        _: *c.GtkEventControllerMotion,
+        x: c.gdouble,
+        y: c.gdouble,
+        ud: ?*anyopaque,
+    ) callconv(.C) void {
+        const self = userdataSelf(ud.?);
+        self.cursor_pos = .{
+            .x = @max(0, @floatCast(f32, x)),
+            .y = @floatCast(f32, y),
+        };
+
+        self.core_surface.cursorPosCallback(self.cursor_pos) catch |err| {
+            log.err("error in cursor pos callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn gtkMouseScroll(
+        _: *c.GtkEventControllerScroll,
+        x: c.gdouble,
+        y: c.gdouble,
+        ud: ?*anyopaque,
+    ) callconv(.C) void {
+        const self = userdataSelf(ud.?);
+        self.core_surface.scrollCallback(x, y * -1) catch |err| {
+            log.err("error in scroll callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn gtkKeyPressed(
+        _: *c.GtkEventControllerKey,
+        keyval: c.guint,
+        keycode: c.guint,
+        state: c.GdkModifierType,
+        ud: ?*anyopaque,
+    ) callconv(.C) c.gboolean {
+        _ = keycode;
+
+        const key = translateKey(keyval);
+        const mods = translateMods(state);
+        const self = userdataSelf(ud.?);
+        log.debug("key-press key={} mods={}", .{ key, mods });
+        self.core_surface.keyCallback(.press, key, mods) catch |err| {
+            log.err("error in key callback err={}", .{err});
+            return 0;
+        };
+
+        return 0;
+    }
+
+    fn gtkKeyReleased(
+        _: *c.GtkEventControllerKey,
+        keyval: c.guint,
+        keycode: c.guint,
+        state: c.GdkModifierType,
+        ud: ?*anyopaque,
+    ) callconv(.C) c.gboolean {
+        _ = keycode;
+
+        const key = translateKey(keyval);
+        const mods = translateMods(state);
+        const self = userdataSelf(ud.?);
+        self.core_surface.keyCallback(.release, key, mods) catch |err| {
+            log.err("error in key callback err={}", .{err});
+            return 0;
+        };
+
+        return 0;
+    }
+
+    fn gtkInputCommit(
+        _: *c.GtkIMContext,
+        bytes: [*:0]u8,
+        ud: ?*anyopaque,
+    ) callconv(.C) void {
+        const str = std.mem.sliceTo(bytes, 0);
+        const view = std.unicode.Utf8View.init(str) catch |err| {
+            log.warn("cannot build utf8 view over input: {}", .{err});
+            return;
+        };
+
+        const self = userdataSelf(ud.?);
+        var it = view.iterator();
+        while (it.nextCodepoint()) |cp| {
+            self.core_surface.charCallback(cp) catch |err| {
+                log.err("error in char callback err={}", .{err});
+                return;
+            };
+        }
+    }
+
+    fn gtkFocusEnter(_: *c.GtkEventControllerFocus, ud: ?*anyopaque) callconv(.C) void {
+        const self = userdataSelf(ud.?);
+        self.core_surface.focusCallback(true) catch |err| {
+            log.err("error in focus callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn gtkFocusLeave(_: *c.GtkEventControllerFocus, ud: ?*anyopaque) callconv(.C) void {
+        const self = userdataSelf(ud.?);
+        self.core_surface.focusCallback(false) catch |err| {
+            log.err("error in focus callback err={}", .{err});
+            return;
+        };
+    }
+
+    fn userdataSelf(ud: *anyopaque) *Surface {
+        return @ptrCast(*Surface, @alignCast(@alignOf(Surface), ud));
+    }
+};
+
+fn translateMouseButton(button: c.guint) input.MouseButton {
+    return switch (button) {
+        1 => .left,
+        2 => .middle,
+        3 => .right,
+        4 => .four,
+        5 => .five,
+        6 => .six,
+        7 => .seven,
+        8 => .eight,
+        9 => .nine,
+        10 => .ten,
+        11 => .eleven,
+        else => .unknown,
+    };
+}
+
+fn translateMods(state: c.GdkModifierType) input.Mods {
+    var mods: input.Mods = .{};
+    if (state & c.GDK_SHIFT_MASK != 0) mods.shift = true;
+    if (state & c.GDK_CONTROL_MASK != 0) mods.ctrl = true;
+    if (state & c.GDK_ALT_MASK != 0) mods.alt = true;
+    if (state & c.GDK_SUPER_MASK != 0) mods.super = true;
+
+    // Lock is dependent on the X settings but we just assume caps lock.
+    if (state & c.GDK_LOCK_MASK != 0) mods.caps_lock = true;
+    return mods;
+}
+
+fn translateKey(keyval: c.guint) input.Key {
+    return switch (keyval) {
+        c.GDK_KEY_a => .a,
+        c.GDK_KEY_b => .b,
+        c.GDK_KEY_c => .c,
+        c.GDK_KEY_d => .d,
+        c.GDK_KEY_e => .e,
+        c.GDK_KEY_f => .f,
+        c.GDK_KEY_g => .g,
+        c.GDK_KEY_h => .h,
+        c.GDK_KEY_i => .i,
+        c.GDK_KEY_j => .j,
+        c.GDK_KEY_k => .k,
+        c.GDK_KEY_l => .l,
+        c.GDK_KEY_m => .m,
+        c.GDK_KEY_n => .n,
+        c.GDK_KEY_o => .o,
+        c.GDK_KEY_p => .p,
+        c.GDK_KEY_q => .q,
+        c.GDK_KEY_r => .r,
+        c.GDK_KEY_s => .s,
+        c.GDK_KEY_t => .t,
+        c.GDK_KEY_u => .u,
+        c.GDK_KEY_v => .v,
+        c.GDK_KEY_w => .w,
+        c.GDK_KEY_x => .x,
+        c.GDK_KEY_y => .y,
+        c.GDK_KEY_z => .z,
+
+        c.GDK_KEY_0 => .zero,
+        c.GDK_KEY_1 => .one,
+        c.GDK_KEY_2 => .two,
+        c.GDK_KEY_3 => .three,
+        c.GDK_KEY_4 => .four,
+        c.GDK_KEY_5 => .five,
+        c.GDK_KEY_6 => .six,
+        c.GDK_KEY_7 => .seven,
+        c.GDK_KEY_8 => .eight,
+        c.GDK_KEY_9 => .nine,
+
+        c.GDK_KEY_semicolon => .semicolon,
+        c.GDK_KEY_space => .space,
+        c.GDK_KEY_apostrophe => .apostrophe,
+        c.GDK_KEY_comma => .comma,
+        c.GDK_KEY_grave => .grave_accent, // `
+        c.GDK_KEY_period => .period,
+        c.GDK_KEY_slash => .slash,
+        c.GDK_KEY_minus => .minus,
+        c.GDK_KEY_equal => .equal,
+        c.GDK_KEY_bracketleft => .left_bracket, // [
+        c.GDK_KEY_bracketright => .right_bracket, // ]
+        c.GDK_KEY_backslash => .backslash, // /
+
+        c.GDK_KEY_Up => .up,
+        c.GDK_KEY_Down => .down,
+        c.GDK_KEY_Right => .right,
+        c.GDK_KEY_Left => .left,
+        c.GDK_KEY_Home => .home,
+        c.GDK_KEY_End => .end,
+        c.GDK_KEY_Insert => .insert,
+        c.GDK_KEY_Delete => .delete,
+        c.GDK_KEY_Caps_Lock => .caps_lock,
+        c.GDK_KEY_Scroll_Lock => .scroll_lock,
+        c.GDK_KEY_Num_Lock => .num_lock,
+        c.GDK_KEY_Page_Up => .page_up,
+        c.GDK_KEY_Page_Down => .page_down,
+        c.GDK_KEY_Escape => .escape,
+        c.GDK_KEY_Return => .enter,
+        c.GDK_KEY_Tab => .tab,
+        c.GDK_KEY_BackSpace => .backspace,
+        c.GDK_KEY_Print => .print_screen,
+        c.GDK_KEY_Pause => .pause,
+
+        c.GDK_KEY_F1 => .f1,
+        c.GDK_KEY_F2 => .f2,
+        c.GDK_KEY_F3 => .f3,
+        c.GDK_KEY_F4 => .f4,
+        c.GDK_KEY_F5 => .f5,
+        c.GDK_KEY_F6 => .f6,
+        c.GDK_KEY_F7 => .f7,
+        c.GDK_KEY_F8 => .f8,
+        c.GDK_KEY_F9 => .f9,
+        c.GDK_KEY_F10 => .f10,
+        c.GDK_KEY_F11 => .f11,
+        c.GDK_KEY_F12 => .f12,
+        c.GDK_KEY_F13 => .f13,
+        c.GDK_KEY_F14 => .f14,
+        c.GDK_KEY_F15 => .f15,
+        c.GDK_KEY_F16 => .f16,
+        c.GDK_KEY_F17 => .f17,
+        c.GDK_KEY_F18 => .f18,
+        c.GDK_KEY_F19 => .f19,
+        c.GDK_KEY_F20 => .f20,
+        c.GDK_KEY_F21 => .f21,
+        c.GDK_KEY_F22 => .f22,
+        c.GDK_KEY_F23 => .f23,
+        c.GDK_KEY_F24 => .f24,
+        c.GDK_KEY_F25 => .f25,
+
+        c.GDK_KEY_KP_0 => .kp_0,
+        c.GDK_KEY_KP_1 => .kp_1,
+        c.GDK_KEY_KP_2 => .kp_2,
+        c.GDK_KEY_KP_3 => .kp_3,
+        c.GDK_KEY_KP_4 => .kp_4,
+        c.GDK_KEY_KP_5 => .kp_5,
+        c.GDK_KEY_KP_6 => .kp_6,
+        c.GDK_KEY_KP_7 => .kp_7,
+        c.GDK_KEY_KP_8 => .kp_8,
+        c.GDK_KEY_KP_9 => .kp_9,
+        c.GDK_KEY_KP_Decimal => .kp_decimal,
+        c.GDK_KEY_KP_Divide => .kp_divide,
+        c.GDK_KEY_KP_Multiply => .kp_multiply,
+        c.GDK_KEY_KP_Subtract => .kp_subtract,
+        c.GDK_KEY_KP_Add => .kp_add,
+        c.GDK_KEY_KP_Enter => .kp_enter,
+        c.GDK_KEY_KP_Equal => .kp_equal,
+
+        c.GDK_KEY_Shift_L => .left_shift,
+        c.GDK_KEY_Control_L => .left_control,
+        c.GDK_KEY_Alt_L => .left_alt,
+        c.GDK_KEY_Super_L => .left_super,
+        c.GDK_KEY_Shift_R => .right_shift,
+        c.GDK_KEY_Control_R => .right_control,
+        c.GDK_KEY_Alt_R => .right_alt,
+        c.GDK_KEY_Super_R => .right_super,
+
+        else => .invalid,
+    };
+}
diff --git a/src/apprt/structs.zig b/src/apprt/structs.zig
index 2cdb8be9e..9ca2434d4 100644
--- a/src/apprt/structs.zig
+++ b/src/apprt/structs.zig
@@ -6,8 +6,8 @@ pub const ContentScale = struct {
     y: f32,
 };
 
-/// The size of the window in pixels.
-pub const WindowSize = struct {
+/// The size of the surface in pixels.
+pub const SurfaceSize = struct {
     width: u32,
     height: u32,
 };
diff --git a/src/apprt/Window.zig b/src/apprt/surface.zig
similarity index 56%
rename from src/apprt/Window.zig
rename to src/apprt/surface.zig
index 159b6e92a..0e6439a41 100644
--- a/src/apprt/Window.zig
+++ b/src/apprt/surface.zig
@@ -1,15 +1,15 @@
 const App = @import("../App.zig");
-const Window = @import("../Window.zig");
+const Surface = @import("../Surface.zig");
 const renderer = @import("../renderer.zig");
 const termio = @import("../termio.zig");
 
-/// The message types that can be sent to a single window.
+/// The message types that can be sent to a single surface.
 pub const Message = union(enum) {
     /// Represents a write request. Magic number comes from the max size
     /// we want this union to be.
     pub const WriteReq = termio.MessageData(u8, 256);
 
-    /// Set the title of the window.
+    /// Set the title of the surface.
     /// TODO: we should change this to a "WriteReq" style structure in
     /// the termio message so that we can more efficiently send strings
     /// of any length
@@ -25,26 +25,25 @@ pub const Message = union(enum) {
     clipboard_write: WriteReq,
 };
 
-/// A window mailbox.
+/// A surface mailbox.
 pub const Mailbox = struct {
-    window: *Window,
-    app: *App.Mailbox,
+    surface: *Surface,
+    app: App.Mailbox,
 
-    /// Send a message to the window.
-    pub fn push(self: Mailbox, msg: Message, timeout: App.Mailbox.Timeout) App.Mailbox.Size {
-        // Window message sending is actually implemented on the app
-        // thread, so we have to rewrap the message with our window
+    /// Send a message to the surface.
+    pub fn push(
+        self: Mailbox,
+        msg: Message,
+        timeout: App.Mailbox.Queue.Timeout,
+    ) App.Mailbox.Queue.Size {
+        // Surface message sending is actually implemented on the app
+        // thread, so we have to rewrap the message with our surface
         // pointer and send it to the app thread.
-        const result = self.app.push(.{
-            .window_message = .{
-                .window = self.window,
+        return self.app.push(.{
+            .surface_message = .{
+                .surface = self.surface,
                 .message = msg,
             },
         }, timeout);
-
-        // Wake up our app loop
-        self.window.app.wakeup();
-
-        return result;
     }
 };
diff --git a/src/build_config.zig b/src/build_config.zig
index 2baaa48b8..ddaf9c14c 100644
--- a/src/build_config.zig
+++ b/src/build_config.zig
@@ -4,15 +4,19 @@
 //! to shim logic and values into them later.
 const std = @import("std");
 const builtin = @import("builtin");
+const options = @import("build_options");
 const assert = std.debug.assert;
 
 /// The artifact we're producing. This can be used to determine if we're
 /// building a standalone exe, an embedded lib, etc.
 pub const artifact = Artifact.detect();
 
+/// The runtime to back exe artifacts with.
+pub const app_runtime = options.app_runtime;
+
 /// Whether our devmode UI is enabled or not. This requires imgui to be
 /// compiled.
-pub const devmode_enabled = artifact == .exe;
+pub const devmode_enabled = artifact == .exe and app_runtime == .glfw;
 
 pub const Artifact = enum {
     /// Standalone executable
diff --git a/src/input/mouse.zig b/src/input/mouse.zig
index e1059e4c0..224abef35 100644
--- a/src/input/mouse.zig
+++ b/src/input/mouse.zig
@@ -32,6 +32,7 @@ pub const MouseButton = enum(c_int) {
         break :max cur;
     };
 
+    unknown = 0,
     left = 1,
     right = 2,
     middle = 3,
diff --git a/src/main.zig b/src/main.zig
index 48c4d2a71..7489d69fd 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const builtin = @import("builtin");
+const build_config = @import("build_config.zig");
 const options = @import("build_options");
 const glfw = @import("glfw");
 const macos = @import("macos");
@@ -10,6 +11,7 @@ const fontconfig = @import("fontconfig");
 const harfbuzz = @import("harfbuzz");
 const renderer = @import("renderer.zig");
 const xdg = @import("xdg.zig");
+const apprt = @import("apprt.zig");
 
 const App = @import("App.zig");
 const cli_args = @import("cli_args.zig");
@@ -86,16 +88,21 @@ pub fn main() !void {
         }
     }
     try config.finalize();
-    std.log.debug("config={}", .{config});
+    //std.log.debug("config={}", .{config});
 
-    // We want to log all our errors
-    glfw.setErrorCallback(glfwErrorCallback);
-
-    // Run our app with a single initial window to start.
-    var app = try App.create(alloc, .{}, &config);
+    // Create our app state
+    var app = try App.create(alloc, &config);
     defer app.destroy();
-    _ = try app.newWindow(.{});
-    try app.run();
+
+    // Create our runtime app
+    var app_runtime = try apprt.App.init(app, .{});
+    defer app_runtime.terminate();
+
+    // Create an initial window
+    try app_runtime.newWindow(null);
+
+    // Run the GUI event loop
+    try app_runtime.run();
 }
 
 // Required by tracy/tracy.zig to enable/disable tracy support.
@@ -151,20 +158,6 @@ pub const std_options = struct {
     }
 };
 
-fn glfwErrorCallback(code: glfw.ErrorCode, desc: [:0]const u8) void {
-    std.log.warn("glfw error={} message={s}", .{ code, desc });
-
-    // Workaround for: https://github.com/ocornut/imgui/issues/5908
-    // If we get an invalid value with "scancode" in the message we assume
-    // it is from the glfw key callback that imgui sets and we clear the
-    // error so that our future code doesn't crash.
-    if (code == glfw.ErrorCode.InvalidValue and
-        std.mem.indexOf(u8, desc, "scancode") != null)
-    {
-        _ = glfw.getError();
-    }
-}
-
 /// This represents the global process state. There should only
 /// be one of these at any given moment. This is extracted into a dedicated
 /// struct because it is reused by main and the static C lib.
diff --git a/src/main_c.zig b/src/main_c.zig
index 344d477bb..05cf43897 100644
--- a/src/main_c.zig
+++ b/src/main_c.zig
@@ -10,10 +10,10 @@ const std = @import("std");
 const assert = std.debug.assert;
 const builtin = @import("builtin");
 const main = @import("main.zig");
+const apprt = @import("apprt.zig");
 
 // Some comptime assertions that our C API depends on.
 comptime {
-    const apprt = @import("apprt.zig");
     assert(apprt.runtime == apprt.embedded);
 }
 
@@ -21,7 +21,7 @@ comptime {
 pub const std_options = main.std_options;
 
 pub usingnamespace @import("config.zig").CAPI;
-pub usingnamespace @import("App.zig").CAPI;
+pub usingnamespace apprt.runtime.CAPI;
 
 /// Initialize ghostty global state. It is possible to have more than
 /// one global state but it has zero practical benefit.
diff --git a/src/renderer/Metal.zig b/src/renderer/Metal.zig
index 5157befc9..5e8fcff18 100644
--- a/src/renderer/Metal.zig
+++ b/src/renderer/Metal.zig
@@ -16,7 +16,7 @@ const terminal = @import("../terminal/main.zig");
 const renderer = @import("../renderer.zig");
 const math = @import("../math.zig");
 const DevMode = @import("../DevMode.zig");
-const Window = @import("../Window.zig");
+const Surface = @import("../Surface.zig");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const Terminal = terminal.Terminal;
@@ -32,7 +32,7 @@ const log = std.log.scoped(.metal);
 alloc: std.mem.Allocator,
 
 /// The mailbox for communicating with the window.
-window_mailbox: Window.Mailbox,
+surface_mailbox: apprt.surface.Mailbox,
 
 /// Current cell dimensions for this grid.
 cell_size: renderer.CellSize,
@@ -135,8 +135,8 @@ pub fn glfwWindowHints() glfw.Window.Hints {
 
 /// This is called early right after window creation to setup our
 /// window surface as necessary.
-pub fn windowInit(win: apprt.runtime.Window) !void {
-    _ = win;
+pub fn surfaceInit(surface: *apprt.Surface) !void {
+    _ = surface;
 
     // We don't do anything else here because we want to set everything
     // else up during actual initialization.
@@ -240,7 +240,7 @@ pub fn init(alloc: Allocator, options: renderer.Options) !Metal {
 
     return Metal{
         .alloc = alloc,
-        .window_mailbox = options.window_mailbox,
+        .surface_mailbox = options.surface_mailbox,
         .cell_size = .{ .width = metrics.cell_width, .height = metrics.cell_height },
         .padding = options.padding,
         .focused = true,
@@ -304,7 +304,7 @@ pub fn deinit(self: *Metal) void {
 
 /// This is called just prior to spinning up the renderer thread for
 /// final main thread setup requirements.
-pub fn finalizeWindowInit(self: *const Metal, win: apprt.runtime.Window) !void {
+pub fn finalizeSurfaceInit(self: *const Metal, surface: *apprt.Surface) !void {
     const Info = struct {
         view: objc.Object,
         scaleFactor: f64,
@@ -315,7 +315,7 @@ pub fn finalizeWindowInit(self: *const Metal, win: apprt.runtime.Window) !void {
         apprt.glfw => info: {
             // Everything in glfw is window-oriented so we grab the backing
             // window, then derive everything from that.
-            const nswindow = objc.Object.fromId(glfwNative.getCocoaWindow(win.window).?);
+            const nswindow = objc.Object.fromId(glfwNative.getCocoaWindow(surface.window).?);
             const contentView = objc.Object.fromId(nswindow.getProperty(?*anyopaque, "contentView").?);
             const scaleFactor = nswindow.getProperty(macos.graphics.c.CGFloat, "backingScaleFactor");
             break :info .{
@@ -325,8 +325,8 @@ pub fn finalizeWindowInit(self: *const Metal, win: apprt.runtime.Window) !void {
         },
 
         apprt.embedded => .{
-            .view = win.nsview,
-            .scaleFactor = @floatCast(f64, win.content_scale.x),
+            .view = surface.nsview,
+            .scaleFactor = @floatCast(f64, surface.content_scale.x),
         },
 
         else => @compileError("unsupported apprt for metal"),
@@ -344,11 +344,11 @@ pub fn finalizeWindowInit(self: *const Metal, win: apprt.runtime.Window) !void {
 }
 
 /// This is called if this renderer runs DevMode.
-pub fn initDevMode(self: *const Metal, win: apprt.runtime.Window) !void {
+pub fn initDevMode(self: *const Metal, surface: *apprt.Surface) !void {
     if (DevMode.enabled) {
         // Initialize for our window
         assert(imgui.ImplGlfw.initForOther(
-            @ptrCast(*imgui.ImplGlfw.GLFWWindow, win.window.handle),
+            @ptrCast(*imgui.ImplGlfw.GLFWWindow, surface.window.handle),
             true,
         ));
         assert(imgui.ImplMetal.init(self.device.value));
@@ -366,9 +366,9 @@ pub fn deinitDevMode(self: *const Metal) void {
 }
 
 /// Callback called by renderer.Thread when it begins.
-pub fn threadEnter(self: *const Metal, win: apprt.runtime.Window) !void {
+pub fn threadEnter(self: *const Metal, surface: *apprt.Surface) !void {
     _ = self;
-    _ = win;
+    _ = surface;
 
     // Metal requires no per-thread state.
 }
@@ -442,7 +442,7 @@ pub fn setFontSize(self: *Metal, size: font.face.DesiredSize) !void {
     };
 
     // Notify the window that the cell size changed.
-    _ = self.window_mailbox.push(.{
+    _ = self.surface_mailbox.push(.{
         .cell_size = new_cell_size,
     }, .{ .forever = {} });
 }
@@ -450,10 +450,10 @@ pub fn setFontSize(self: *Metal, size: font.face.DesiredSize) !void {
 /// The primary render callback that is completely thread-safe.
 pub fn render(
     self: *Metal,
-    win: apprt.runtime.Window,
+    surface: *apprt.Surface,
     state: *renderer.State,
 ) !void {
-    _ = win;
+    _ = surface;
 
     // Data we extract out of the critical area.
     const Critical = struct {
@@ -533,8 +533,8 @@ pub fn render(
         critical.draw_cursor,
     );
 
-    // Get our surface (CAMetalDrawable)
-    const surface = self.swapchain.msgSend(objc.Object, objc.sel("nextDrawable"), .{});
+    // Get our drawable (CAMetalDrawable)
+    const drawable = self.swapchain.msgSend(objc.Object, objc.sel("nextDrawable"), .{});
 
     // If our font atlas changed, sync the texture data
     if (self.font_group.atlas_greyscale.modified) {
@@ -572,7 +572,7 @@ pub fn render(
                 // Ghostty in XCode in debug mode it returns a CaptureMTLDrawable
                 // which ironically doesn't implement CAMetalDrawable as a
                 // property so we just send a message.
-                const texture = surface.msgSend(objc.c.id, objc.sel("texture"), .{});
+                const texture = drawable.msgSend(objc.c.id, objc.sel("texture"), .{});
                 attachment.setProperty("loadAction", @enumToInt(MTLLoadAction.clear));
                 attachment.setProperty("storeAction", @enumToInt(MTLStoreAction.store));
                 attachment.setProperty("texture", texture);
@@ -656,7 +656,7 @@ pub fn render(
         }
     }
 
-    buffer.msgSend(void, objc.sel("presentDrawable:"), .{surface.value});
+    buffer.msgSend(void, objc.sel("presentDrawable:"), .{drawable.value});
     buffer.msgSend(void, objc.sel("commit"), .{});
 }
 
diff --git a/src/renderer/OpenGL.zig b/src/renderer/OpenGL.zig
index c8cdf6a26..8f8005b00 100644
--- a/src/renderer/OpenGL.zig
+++ b/src/renderer/OpenGL.zig
@@ -18,19 +18,29 @@ const trace = @import("tracy").trace;
 const math = @import("../math.zig");
 const lru = @import("../lru.zig");
 const DevMode = @import("../DevMode.zig");
-const Window = @import("../Window.zig");
+const Surface = @import("../Surface.zig");
 
 const log = std.log.scoped(.grid);
 
-// The LRU is keyed by (screen, row_id) since we need to cache rows
-// separately for alt screens. By storing that in the key, we very likely
-// have the cache already for when the primary screen is reactivated.
+/// The LRU is keyed by (screen, row_id) since we need to cache rows
+/// separately for alt screens. By storing that in the key, we very likely
+/// have the cache already for when the primary screen is reactivated.
 const CellsLRU = lru.AutoHashMap(struct {
     selection: ?terminal.Selection,
     screen: terminal.Terminal.ScreenType,
     row_id: terminal.Screen.RowHeader.Id,
 }, std.ArrayListUnmanaged(GPUCell));
 
+/// The runtime can request a single-threaded draw by setting this boolean
+/// to true. In this case, the renderer.draw() call is expected to be called
+/// from the runtime.
+pub const single_threaded_draw = if (@hasDecl(apprt.Surface, "opengl_single_threaded_draw"))
+    apprt.Surface.opengl_single_threaded_draw
+else
+    false;
+const DrawMutex = if (single_threaded_draw) std.Thread.Mutex else void;
+const drawMutexZero = if (DrawMutex == void) void{} else .{};
+
 alloc: std.mem.Allocator,
 
 /// Current cell dimensions for this grid.
@@ -89,7 +99,77 @@ focused: bool,
 padding: renderer.Options.Padding,
 
 /// The mailbox for communicating with the window.
-window_mailbox: Window.Mailbox,
+surface_mailbox: apprt.surface.Mailbox,
+
+/// Deferred operations. This is used to apply changes to the OpenGL context.
+/// Some runtimes (GTK) do not support multi-threading so to keep our logic
+/// simple we apply all OpenGL context changes in the render() call.
+deferred_screen_size: ?SetScreenSize = null,
+deferred_font_size: ?SetFontSize = null,
+
+/// If we're drawing with single threaded operations
+draw_mutex: DrawMutex = drawMutexZero,
+
+/// Current background to draw. This may not match self.background if the
+/// terminal is in reversed mode.
+draw_background: terminal.color.RGB,
+
+/// Defererred OpenGL operation to update the screen size.
+const SetScreenSize = struct {
+    size: renderer.ScreenSize,
+
+    fn apply(self: SetScreenSize, r: *const OpenGL) !void {
+        // Apply our padding
+        const padding = r.padding.explicit.add(if (r.padding.balance)
+            renderer.Padding.balanced(self.size, r.gridSize(self.size), r.cell_size)
+        else
+            .{});
+        const padded_size = self.size.subPadding(padding);
+
+        log.debug("GL api: screen size padded={} screen={} grid={} cell={} padding={}", .{
+            padded_size,
+            self.size,
+            r.gridSize(self.size),
+            r.cell_size,
+            r.padding.explicit,
+        });
+
+        // Update our viewport for this context to be the entire window.
+        // OpenGL works in pixels, so we have to use the pixel size.
+        try gl.viewport(
+            0,
+            0,
+            @intCast(i32, self.size.width),
+            @intCast(i32, self.size.height),
+        );
+
+        // Update the projection uniform within our shader
+        try r.program.setUniform(
+            "projection",
+
+            // 2D orthographic projection with the full w/h
+            math.ortho2d(
+                -1 * padding.left,
+                @intToFloat(f32, padded_size.width) + padding.right,
+                @intToFloat(f32, padded_size.height) + padding.bottom,
+                -1 * padding.top,
+            ),
+        );
+    }
+};
+
+const SetFontSize = struct {
+    metrics: font.face.Metrics,
+
+    fn apply(self: SetFontSize, r: *const OpenGL) !void {
+        try r.program.setUniform(
+            "cell_size",
+            @Vector(2, f32){ self.metrics.cell_width, self.metrics.cell_height },
+        );
+        try r.program.setUniform("strikethrough_position", self.metrics.strikethrough_position);
+        try r.program.setUniform("strikethrough_thickness", self.metrics.strikethrough_thickness);
+    }
+};
 
 /// The raw structure that maps directly to the buffer sent to the vertex shader.
 /// This must be "extern" so that the field order is not reordered by the
@@ -173,14 +253,11 @@ pub fn init(alloc: Allocator, options: renderer.Options) !OpenGL {
     );
 
     // Setup our font metrics uniform
-    const metrics = try resetFontMetrics(alloc, program, options.font_group);
+    const metrics = try resetFontMetrics(alloc, options.font_group);
 
     // Set our cell dimensions
     const pbind = try program.use();
     defer pbind.unbind();
-    try program.setUniform("cell_size", @Vector(2, f32){ metrics.cell_width, metrics.cell_height });
-    try program.setUniform("strikethrough_position", metrics.strikethrough_position);
-    try program.setUniform("strikethrough_thickness", metrics.strikethrough_thickness);
 
     // Set all of our texture indexes
     try program.setUniform("text", 0);
@@ -301,6 +378,7 @@ pub fn init(alloc: Allocator, options: renderer.Options) !OpenGL {
         .cursor_color = if (options.config.@"cursor-color") |col| col.toTerminalRGB() else null,
         .background = options.config.background.toTerminalRGB(),
         .foreground = options.config.foreground.toTerminalRGB(),
+        .draw_background = options.config.background.toTerminalRGB(),
         .selection_background = if (options.config.@"selection-background") |bg|
             bg.toTerminalRGB()
         else
@@ -311,7 +389,8 @@ pub fn init(alloc: Allocator, options: renderer.Options) !OpenGL {
             null,
         .focused = true,
         .padding = options.padding,
-        .window_mailbox = options.window_mailbox,
+        .surface_mailbox = options.surface_mailbox,
+        .deferred_font_size = .{ .metrics = metrics },
     };
 }
 
@@ -362,12 +441,26 @@ pub fn glfwWindowHints() glfw.Window.Hints {
     };
 }
 
-/// This is called early right after window creation to setup our
-/// window surface as necessary.
-pub fn windowInit(win: apprt.runtime.Window) !void {
+/// This is called early right after surface creation.
+pub fn surfaceInit(surface: *apprt.Surface) !void {
     // Treat this like a thread entry
     const self: OpenGL = undefined;
-    try self.threadEnter(win);
+
+    switch (apprt.runtime) {
+        else => @compileError("unsupported app runtime for OpenGL"),
+
+        apprt.gtk => {
+            // GTK uses global OpenGL context so we load from null.
+            const version = try gl.glad.load(null);
+            errdefer gl.glad.unload();
+            log.info("loaded OpenGL {}.{}", .{
+                gl.glad.versionMajor(@intCast(c_uint, version)),
+                gl.glad.versionMinor(@intCast(c_uint, version)),
+            });
+        },
+
+        apprt.glfw => try self.threadEnter(surface),
+    }
 
     // Blending for text. We use GL_ONE here because we should be using
     // premultiplied alpha for all our colors in our fragment shaders.
@@ -388,19 +481,19 @@ pub fn windowInit(win: apprt.runtime.Window) !void {
 
 /// This is called just prior to spinning up the renderer thread for
 /// final main thread setup requirements.
-pub fn finalizeWindowInit(self: *const OpenGL, win: apprt.runtime.Window) !void {
+pub fn finalizeSurfaceInit(self: *const OpenGL, surface: *apprt.Surface) !void {
     _ = self;
-    _ = win;
+    _ = surface;
 }
 
 /// This is called if this renderer runs DevMode.
-pub fn initDevMode(self: *const OpenGL, win: apprt.runtime.Window) !void {
+pub fn initDevMode(self: *const OpenGL, surface: *apprt.Surface) !void {
     _ = self;
 
     if (DevMode.enabled) {
         // Initialize for our window
         assert(imgui.ImplGlfw.initForOpenGL(
-            @ptrCast(*imgui.ImplGlfw.GLFWWindow, win.window.handle),
+            @ptrCast(*imgui.ImplGlfw.GLFWWindow, surface.window.handle),
             true,
         ));
         assert(imgui.ImplOpenGL3.init("#version 330 core"));
@@ -418,34 +511,58 @@ pub fn deinitDevMode(self: *const OpenGL) void {
 }
 
 /// Callback called by renderer.Thread when it begins.
-pub fn threadEnter(self: *const OpenGL, win: apprt.runtime.Window) !void {
+pub fn threadEnter(self: *const OpenGL, surface: *apprt.Surface) !void {
     _ = self;
 
-    // We need to make the OpenGL context current. OpenGL requires
-    // that a single thread own the a single OpenGL context (if any). This
-    // ensures that the context switches over to our thread. Important:
-    // the prior thread MUST have detached the context prior to calling
-    // this entrypoint.
-    glfw.makeContextCurrent(win.window);
-    errdefer glfw.makeContextCurrent(null);
-    glfw.swapInterval(1);
+    switch (apprt.runtime) {
+        else => @compileError("unsupported app runtime for OpenGL"),
 
-    // Load OpenGL bindings. This API is context-aware so this sets
-    // a threadlocal context for these pointers.
-    const version = try gl.glad.load(&glfw.getProcAddress);
-    errdefer gl.glad.unload();
-    log.info("loaded OpenGL {}.{}", .{
-        gl.glad.versionMajor(@intCast(c_uint, version)),
-        gl.glad.versionMinor(@intCast(c_uint, version)),
-    });
+        apprt.gtk => {
+            // GTK doesn't support threaded OpenGL operations as far as I can
+            // tell, so we use the renderer thread to setup all the state
+            // but then do the actual draws and texture syncs and all that
+            // on the main thread. As such, we don't do anything here.
+        },
+
+        apprt.glfw => {
+            // We need to make the OpenGL context current. OpenGL requires
+            // that a single thread own the a single OpenGL context (if any). This
+            // ensures that the context switches over to our thread. Important:
+            // the prior thread MUST have detached the context prior to calling
+            // this entrypoint.
+            glfw.makeContextCurrent(surface.window);
+            errdefer glfw.makeContextCurrent(null);
+            glfw.swapInterval(1);
+
+            // Load OpenGL bindings. This API is context-aware so this sets
+            // a threadlocal context for these pointers.
+            const version = try gl.glad.load(&glfw.getProcAddress);
+            errdefer gl.glad.unload();
+            log.info("loaded OpenGL {}.{}", .{
+                gl.glad.versionMajor(@intCast(c_uint, version)),
+                gl.glad.versionMinor(@intCast(c_uint, version)),
+            });
+        },
+    }
 }
 
 /// Callback called by renderer.Thread when it exits.
 pub fn threadExit(self: *const OpenGL) void {
     _ = self;
 
-    gl.glad.unload();
-    glfw.makeContextCurrent(null);
+    switch (apprt.runtime) {
+        else => @compileError("unsupported app runtime for OpenGL"),
+
+        apprt.gtk => {
+            // We don't need to do any unloading for GTK because we may
+            // be sharing the global bindings with other windows.
+        },
+
+        apprt.glfw => {
+            gl.glad.unload();
+            glfw.makeContextCurrent(null);
+        },
+    }
 }
 
 /// Callback when the focus changes for the terminal this is rendering.
@@ -466,6 +583,9 @@ pub fn blinkCursor(self: *OpenGL, reset: bool) void {
 ///
 /// Must be called on the render thread.
 pub fn setFontSize(self: *OpenGL, size: font.face.DesiredSize) !void {
+    if (single_threaded_draw) self.draw_mutex.lock();
+    defer if (single_threaded_draw) self.draw_mutex.unlock();
+
     log.info("set font size={}", .{size});
 
     // Set our new size, this will also reset our font atlas.
@@ -475,7 +595,10 @@ pub fn setFontSize(self: *OpenGL, size: font.face.DesiredSize) !void {
     self.resetCellsLRU();
 
     // Reset our GPU uniforms
-    const metrics = try resetFontMetrics(self.alloc, self.program, self.font_group);
+    const metrics = try resetFontMetrics(self.alloc, self.font_group);
+
+    // Defer our GPU updates
+    self.deferred_font_size = .{ .metrics = metrics };
 
     // Recalculate our cell size. If it is the same as before, then we do
     // nothing since the grid size couldn't have possibly changed.
@@ -484,7 +607,7 @@ pub fn setFontSize(self: *OpenGL, size: font.face.DesiredSize) !void {
     self.cell_size = new_cell_size;
 
     // Notify the window that the cell size changed.
-    _ = self.window_mailbox.push(.{
+    _ = self.surface_mailbox.push(.{
         .cell_size = new_cell_size,
     }, .{ .forever = {} });
 }
@@ -493,7 +616,6 @@ pub fn setFontSize(self: *OpenGL, size: font.face.DesiredSize) !void {
 /// down to the GPU.
 fn resetFontMetrics(
     alloc: Allocator,
-    program: gl.Program,
     font_group: *font.GroupCache,
 ) !font.face.Metrics {
     // Get our cell metrics based on a regular font ascii 'M'. Why 'M'?
@@ -514,20 +636,13 @@ fn resetFontMetrics(
         .underline_position = @floatToInt(u32, metrics.underline_position),
     };
 
-    // Set our uniforms that rely on metrics
-    const pbind = try program.use();
-    defer pbind.unbind();
-    try program.setUniform("cell_size", @Vector(2, f32){ metrics.cell_width, metrics.cell_height });
-    try program.setUniform("strikethrough_position", metrics.strikethrough_position);
-    try program.setUniform("strikethrough_thickness", metrics.strikethrough_thickness);
-
     return metrics;
 }
 
 /// The primary render callback that is completely thread-safe.
 pub fn render(
     self: *OpenGL,
-    win: apprt.runtime.Window,
+    surface: *apprt.Surface,
     state: *renderer.State,
 ) !void {
     // Data we extract out of the critical area.
@@ -568,12 +683,14 @@ pub fn render(
 
         // Build our devmode draw data
         const devmode_data = devmode_data: {
-            if (state.devmode) |dm| {
-                if (dm.visible) {
-                    imgui.ImplOpenGL3.newFrame();
-                    imgui.ImplGlfw.newFrame();
-                    try dm.update();
-                    break :devmode_data try dm.render();
+            if (DevMode.enabled) {
+                if (state.devmode) |dm| {
+                    if (dm.visible) {
+                        imgui.ImplOpenGL3.newFrame();
+                        imgui.ImplGlfw.newFrame();
+                        try dm.update();
+                        break :devmode_data try dm.render();
+                    }
                 }
             }
 
@@ -613,37 +730,42 @@ pub fn render(
     };
     defer critical.screen.deinit();
 
-    // Build our GPU cells
-    try self.rebuildCells(
-        critical.active_screen,
-        critical.selection,
-        &critical.screen,
-        critical.draw_cursor,
-    );
+    // Grab our draw mutex if we have it and update our data
+    {
+        if (single_threaded_draw) self.draw_mutex.lock();
+        defer if (single_threaded_draw) self.draw_mutex.unlock();
 
-    // Try to flush our atlas, this will only do something if there
-    // are changes to the atlas.
-    try self.flushAtlas();
+        // Set our draw data
+        self.draw_background = critical.gl_bg;
 
-    // Clear the surface
-    gl.clearColor(
-        @intToFloat(f32, critical.gl_bg.r) / 255,
-        @intToFloat(f32, critical.gl_bg.g) / 255,
-        @intToFloat(f32, critical.gl_bg.b) / 255,
-        1.0,
-    );
-    gl.clear(gl.c.GL_COLOR_BUFFER_BIT);
+        // Build our GPU cells
+        try self.rebuildCells(
+            critical.active_screen,
+            critical.selection,
+            &critical.screen,
+            critical.draw_cursor,
+        );
+    }
+
+    // We're out of the critical path now. Let's render. We only render if
+    // we're not single threaded. If we're single threaded we expect the
+    // runtime to call draw.
+    if (single_threaded_draw) return;
 
-    // We're out of the critical path now. Let's first render our terminal.
     try self.draw();
 
     // If we have devmode, then render that
-    if (critical.devmode_data) |data| {
-        imgui.ImplOpenGL3.renderDrawData(data);
+    if (DevMode.enabled) {
+        if (critical.devmode_data) |data| {
+            imgui.ImplOpenGL3.renderDrawData(data);
+        }
     }
 
     // Swap our window buffers
-    win.window.swapBuffers();
+    switch (apprt.runtime) {
+        else => @compileError("unsupported runtime"),
+        apprt.glfw => surface.window.swapBuffers(),
+    }
 }
 
 /// rebuildCells rebuilds all the GPU cells from our CPU state. This is a
@@ -1050,7 +1172,7 @@ pub fn updateCell(
 
 /// Returns the grid size for a given screen size. This is safe to call
 /// on any thread.
-fn gridSize(self: *OpenGL, screen_size: renderer.ScreenSize) renderer.GridSize {
+fn gridSize(self: *const OpenGL, screen_size: renderer.ScreenSize) renderer.GridSize {
     return renderer.GridSize.init(
         screen_size.subPadding(self.padding.explicit),
         self.cell_size,
@@ -1060,17 +1182,13 @@ fn gridSize(self: *OpenGL, screen_size: renderer.ScreenSize) renderer.GridSize {
 /// Set the screen size for rendering. This will update the projection
 /// used for the shader so that the scaling of the grid is correct.
 pub fn setScreenSize(self: *OpenGL, dim: renderer.ScreenSize) !void {
+    if (single_threaded_draw) self.draw_mutex.lock();
+    defer if (single_threaded_draw) self.draw_mutex.unlock();
+
     // Recalculate the rows/columns.
     const grid_size = self.gridSize(dim);
 
-    // Apply our padding
-    const padding = self.padding.explicit.add(if (self.padding.balance)
-        renderer.Padding.balanced(dim, grid_size, self.cell_size)
-    else .{});
-    const padded_dim = dim.subPadding(padding);
-
-    log.debug("screen size padded={} screen={} grid={} cell={} padding={}", .{
-        padded_dim,
+    log.debug("screen size screen={} grid={} cell={} padding={}", .{
         dim,
         grid_size,
         self.cell_size,
@@ -1092,31 +1210,8 @@ pub fn setScreenSize(self: *OpenGL, dim: renderer.ScreenSize) !void {
     self.alloc.free(self.font_shaper.cell_buf);
     self.font_shaper.cell_buf = shape_buf;
 
-    // Update our viewport for this context to be the entire window.
-    // OpenGL works in pixels, so we have to use the pixel size.
-    try gl.viewport(
-        0,
-        0,
-        @intCast(i32, dim.width),
-        @intCast(i32, dim.height),
-    );
-
-    // Update the projection uniform within our shader
-    {
-        const bind = try self.program.use();
-        defer bind.unbind();
-        try self.program.setUniform(
-            "projection",
-
-            // 2D orthographic projection with the full w/h
-            math.ortho2d(
-                -1 * padding.left,
-                @intToFloat(f32, padded_dim.width) + padding.right,
-                @intToFloat(f32, padded_dim.height) + padding.bottom,
-                -1 * padding.top,
-            ),
-        );
-    }
+    // Defer our OpenGL updates
+    self.deferred_screen_size = .{ .size = dim };
 }
 
 /// Updates the font texture atlas if it is dirty.
@@ -1196,9 +1291,26 @@ pub fn draw(self: *OpenGL) !void {
     const t = trace(@src());
     defer t.end();
 
+    // If we're in single-threaded more we grab a lock since we use shared data.
+    if (single_threaded_draw) self.draw_mutex.lock();
+    defer if (single_threaded_draw) self.draw_mutex.unlock();
+
     // If we have no cells to render, then we render nothing.
     if (self.cells.items.len == 0) return;
 
+    // Try to flush our atlas, this will only do something if there
+    // are changes to the atlas.
+    try self.flushAtlas();
+
+    // Clear the surface
+    gl.clearColor(
+        @intToFloat(f32, self.draw_background.r) / 255,
+        @intToFloat(f32, self.draw_background.g) / 255,
+        @intToFloat(f32, self.draw_background.b) / 255,
+        1.0,
+    );
+    gl.clear(gl.c.GL_COLOR_BUFFER_BIT);
+
     // Setup our VAO
     try self.vao.bind();
     defer gl.VertexArray.unbind() catch null;
@@ -1224,6 +1336,16 @@ pub fn draw(self: *OpenGL) !void {
     const pbind = try self.program.use();
     defer pbind.unbind();
 
+    // If we have deferred operations, run them.
+    if (self.deferred_screen_size) |v| {
+        try v.apply(self);
+        self.deferred_screen_size = null;
+    }
+    if (self.deferred_font_size) |v| {
+        try v.apply(self);
+        self.deferred_font_size = null;
+    }
+
     try self.drawCells(binding, self.cells_bg);
     try self.drawCells(binding, self.cells);
 }
diff --git a/src/renderer/Options.zig b/src/renderer/Options.zig
index c456c287d..c8b58c8c7 100644
--- a/src/renderer/Options.zig
+++ b/src/renderer/Options.zig
@@ -1,8 +1,8 @@
 //! The options that are used to configure a renderer.
 
+const apprt = @import("../apprt.zig");
 const font = @import("../font/main.zig");
 const renderer = @import("../renderer.zig");
-const Window = @import("../Window.zig");
 const Config = @import("../config.zig").Config;
 
 /// The app configuration.
@@ -14,12 +14,12 @@ font_group: *font.GroupCache,
 /// Padding options for the viewport.
 padding: Padding,
 
-/// The mailbox for sending the window messages. This is only valid
+/// The mailbox for sending the surface messages. This is only valid
 /// once the thread has started and should not be used outside of the thread.
-window_mailbox: Window.Mailbox,
+surface_mailbox: apprt.surface.Mailbox,
 
 pub const Padding = struct {
-    // Explicit padding options, in pixels. The windowing thread is
+    // Explicit padding options, in pixels. The surface thread is
     // expected to convert points to pixels for a given DPI.
     explicit: renderer.Padding,
 
diff --git a/src/renderer/Thread.zig b/src/renderer/Thread.zig
index 534561fa1..12424272d 100644
--- a/src/renderer/Thread.zig
+++ b/src/renderer/Thread.zig
@@ -10,6 +10,7 @@ const apprt = @import("../apprt.zig");
 const BlockingQueue = @import("../blocking_queue.zig").BlockingQueue;
 const tracy = @import("tracy");
 const trace = tracy.trace;
+const App = @import("../App.zig");
 
 const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.renderer_thread);
@@ -47,8 +48,8 @@ cursor_h: xev.Timer,
 cursor_c: xev.Completion = .{},
 cursor_c_cancel: xev.Completion = .{},
 
-/// The window  we're rendering to.
-window: apprt.runtime.Window,
+/// The surface we're rendering to.
+surface: *apprt.Surface,
 
 /// The underlying renderer implementation.
 renderer: *renderer.Renderer,
@@ -60,14 +61,18 @@ state: *renderer.State,
 /// this is a blocking queue so if it is full you will get errors (or block).
 mailbox: *Mailbox,
 
+/// Mailbox to send messages to the app thread
+app_mailbox: App.Mailbox,
+
 /// Initialize the thread. This does not START the thread. This only sets
 /// up all the internal state necessary prior to starting the thread. It
 /// is up to the caller to start the thread with the threadMain entrypoint.
 pub fn init(
     alloc: Allocator,
-    win: apprt.runtime.Window,
+    surface: *apprt.Surface,
     renderer_impl: *renderer.Renderer,
     state: *renderer.State,
+    app_mailbox: App.Mailbox,
 ) !Thread {
     // Create our event loop.
     var loop = try xev.Loop.init(.{});
@@ -100,10 +105,11 @@ pub fn init(
         .stop = stop_h,
         .render_h = render_h,
         .cursor_h = cursor_timer,
-        .window = win,
+        .surface = surface,
         .renderer = renderer_impl,
         .state = state,
         .mailbox = mailbox,
+        .app_mailbox = app_mailbox,
     };
 }
 
@@ -135,7 +141,7 @@ fn threadMain_(self: *Thread) !void {
     // Run our thread start/end callbacks. This is important because some
     // renderers have to do per-thread setup. For example, OpenGL has to set
     // some thread-local state since that is how it works.
-    try self.renderer.threadEnter(self.window);
+    try self.renderer.threadEnter(self.surface);
     defer self.renderer.threadExit();
 
     // Start the async handlers
@@ -305,8 +311,17 @@ fn renderCallback(
         return .disarm;
     };
 
-    t.renderer.render(t.window, t.state) catch |err|
+    t.renderer.render(t.surface, t.state) catch |err|
         log.warn("error rendering err={}", .{err});
+
+    // If we're doing single-threaded GPU calls then we also wake up the
+    // app thread to redraw at this point.
+    if (renderer.Renderer == renderer.OpenGL and
+        renderer.OpenGL.single_threaded_draw)
+    {
+        _ = t.app_mailbox.push(.{ .redraw_surface = t.surface }, .{ .instant = {} });
+    }
+
     return .disarm;
 }
 
diff --git a/src/renderer/opengl/Program.zig b/src/renderer/opengl/Program.zig
index 5140b7517..2e2978363 100644
--- a/src/renderer/opengl/Program.zig
+++ b/src/renderer/opengl/Program.zig
@@ -69,6 +69,7 @@ pub inline fn link(p: Program) !void {
 
 pub inline fn use(p: Program) !Binding {
     glad.context.UseProgram.?(p.id);
+    try errors.getError();
     return Binding{};
 }
 
diff --git a/src/renderer/opengl/Texture.zig b/src/renderer/opengl/Texture.zig
index 446f0a9ad..f52d12859 100644
--- a/src/renderer/opengl/Texture.zig
+++ b/src/renderer/opengl/Texture.zig
@@ -9,6 +9,7 @@ id: c.GLuint,
 
 pub inline fn active(target: c.GLenum) !void {
     glad.context.ActiveTexture.?(target);
+    try errors.getError();
 }
 
 /// Enun for possible texture binding targets.
@@ -153,6 +154,7 @@ pub inline fn create() !Texture {
 /// glBindTexture
 pub inline fn bind(v: Texture, target: Target) !Binding {
     glad.context.BindTexture.?(@enumToInt(target), v.id);
+    try errors.getError();
     return Binding{ .target = target };
 }
 
diff --git a/src/renderer/opengl/VertexArray.zig b/src/renderer/opengl/VertexArray.zig
index 6222a2b68..b86794042 100644
--- a/src/renderer/opengl/VertexArray.zig
+++ b/src/renderer/opengl/VertexArray.zig
@@ -2,6 +2,7 @@ const VertexArray = @This();
 
 const c = @import("c.zig");
 const glad = @import("glad.zig");
+const errors = @import("errors.zig");
 
 id: c.GLuint,
 
@@ -20,6 +21,7 @@ pub inline fn unbind() !void {
 /// glBindVertexArray
 pub inline fn bind(v: VertexArray) !void {
     glad.context.BindVertexArray.?(v.id);
+    try errors.getError();
 }
 
 pub inline fn destroy(v: VertexArray) void {
diff --git a/src/renderer/opengl/glad.zig b/src/renderer/opengl/glad.zig
index 3ee52431e..e1e763da6 100644
--- a/src/renderer/opengl/glad.zig
+++ b/src/renderer/opengl/glad.zig
@@ -23,6 +23,10 @@ pub fn load(getProcAddress: anytype) !c_int {
             getProcAddress,
         )),
 
+        // null proc address means that we are just loading the globally
+        // pointed gl functions
+        @TypeOf(null) => c.gladLoaderLoadGLContext(&context),
+
         // try as-is. If this introduces a compiler error, then add a new case.
         else => c.gladLoadGLContext(&context, getProcAddress),
     };
diff --git a/src/termio/Exec.zig b/src/termio/Exec.zig
index 01e0d300a..86dcf71e8 100644
--- a/src/termio/Exec.zig
+++ b/src/termio/Exec.zig
@@ -8,7 +8,6 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const termio = @import("../termio.zig");
 const Command = @import("../Command.zig");
-const Window = @import("../Window.zig");
 const Pty = @import("../Pty.zig");
 const SegmentedPool = @import("../segmented_pool.zig").SegmentedPool;
 const terminal = @import("../terminal/main.zig");
@@ -16,6 +15,7 @@ const xev = @import("xev");
 const renderer = @import("../renderer.zig");
 const tracy = @import("tracy");
 const trace = tracy.trace;
+const apprt = @import("../apprt.zig");
 const fastmem = @import("../fastmem.zig");
 
 const log = std.log.scoped(.io_exec);
@@ -51,8 +51,8 @@ renderer_wakeup: xev.Async,
 /// The mailbox for notifying the renderer of things.
 renderer_mailbox: *renderer.Thread.Mailbox,
 
-/// The mailbox for communicating with the window.
-window_mailbox: Window.Mailbox,
+/// The mailbox for communicating with the surface.
+surface_mailbox: apprt.surface.Mailbox,
 
 /// The cached grid size whenever a resize is called.
 grid_size: renderer.GridSize,
@@ -83,7 +83,7 @@ pub fn init(alloc: Allocator, opts: termio.Options) !Exec {
         .renderer_state = opts.renderer_state,
         .renderer_wakeup = opts.renderer_wakeup,
         .renderer_mailbox = opts.renderer_mailbox,
-        .window_mailbox = opts.window_mailbox,
+        .surface_mailbox = opts.surface_mailbox,
         .grid_size = opts.grid_size,
         .data = null,
     };
@@ -131,7 +131,7 @@ pub fn threadEnter(self: *Exec, thread: *termio.Thread) !ThreadData {
                 .ev = ev_data_ptr,
                 .terminal = &self.terminal,
                 .grid_size = &self.grid_size,
-                .window_mailbox = self.window_mailbox,
+                .surface_mailbox = self.surface_mailbox,
             },
         },
     };
@@ -638,7 +638,7 @@ const StreamHandler = struct {
     alloc: Allocator,
     grid_size: *renderer.GridSize,
     terminal: *terminal.Terminal,
-    window_mailbox: Window.Mailbox,
+    surface_mailbox: apprt.surface.Mailbox,
 
     /// This is set to true when a message was written to the writer
     /// mailbox. This can be used by callers to determine if they need
@@ -983,7 +983,7 @@ const StreamHandler = struct {
         std.mem.copy(u8, &buf, title);
         buf[title.len] = 0;
 
-        _ = self.window_mailbox.push(.{
+        _ = self.surface_mailbox.push(.{
             .set_title = buf,
         }, .{ .forever = {} });
     }
@@ -995,15 +995,15 @@ const StreamHandler = struct {
 
         // Get clipboard contents
         if (data.len == 1 and data[0] == '?') {
-            _ = self.window_mailbox.push(.{
+            _ = self.surface_mailbox.push(.{
                 .clipboard_read = kind,
             }, .{ .forever = {} });
             return;
         }
 
         // Write clipboard contents
-        _ = self.window_mailbox.push(.{
-            .clipboard_write = try Window.Message.WriteReq.init(
+        _ = self.surface_mailbox.push(.{
+            .clipboard_write = try apprt.surface.Message.WriteReq.init(
                 self.alloc,
                 data,
             ),
diff --git a/src/termio/Options.zig b/src/termio/Options.zig
index d571d0fac..06af6b4d0 100644
--- a/src/termio/Options.zig
+++ b/src/termio/Options.zig
@@ -1,9 +1,9 @@
 //! The options that are used to configure a terminal IO implementation.
 
 const xev = @import("xev");
+const apprt = @import("../apprt.zig");
 const renderer = @import("../renderer.zig");
 const Config = @import("../config.zig").Config;
-const Window = @import("../Window.zig");
 
 /// The size of the terminal grid.
 grid_size: renderer.GridSize,
@@ -15,7 +15,7 @@ screen_size: renderer.ScreenSize,
 config: *const Config,
 
 /// The render state. The IO implementation can modify anything here. The
-/// window thread will setup the initial "terminal" pointer but the IO impl
+/// surface thread will setup the initial "terminal" pointer but the IO impl
 /// is free to change that if that is useful (i.e. doing some sort of dual
 /// terminal implementation.)
 renderer_state: *renderer.State,
@@ -27,5 +27,5 @@ renderer_wakeup: xev.Async,
 /// The mailbox for renderer messages.
 renderer_mailbox: *renderer.Thread.Mailbox,
 
-/// The mailbox for sending the window messages.
-window_mailbox: Window.Mailbox,
+/// The mailbox for sending the surface messages.
+surface_mailbox: apprt.surface.Mailbox,