config: switch to a Surface.Options-based approach

This introduces an ArenaAllocator that models the lifetime of the
Surface.Options structure from initial surface creation command to the
actual surface creation. This implementation is a little rough and
relies on an `anyopaque` pointer (because `extern struct`), but it
demonstrates a more apprt-centric approach.

Still only implemented for embedded apprt and macOS. The other apprts
will need their own plumbing to support this approach.

We can also chose to clean up newConfig() and call Config.shallowClone()
directly after this change.

include/ghostty.h

@@ -31,12 +31,6 @@ typedef void* ghostty_surface_t;
 typedef void* ghostty_inspector_t;
 
 // Enums are up top so we can reference them later.
-typedef enum {
-  GHOSTTY_SURFACE_KIND_SPLIT,
-  GHOSTTY_SURFACE_KIND_TAB,
-  GHOSTTY_SURFACE_KIND_WINDOW,
-} ghostty_surface_kind_e;
-
 typedef enum {
   GHOSTTY_PLATFORM_INVALID,
   GHOSTTY_PLATFORM_MACOS,
@@ -401,7 +395,6 @@ typedef union {
 } ghostty_platform_u;
 
 typedef struct {
-  ghostty_surface_kind_e kind;
   ghostty_platform_e platform_tag;
   ghostty_platform_u platform;
   void* userdata;
@@ -409,6 +402,7 @@ typedef struct {
   float font_size;
   const char* working_directory;
   const char* command;
+  void* _arena;
 } ghostty_surface_config_s;
 
 typedef void (*ghostty_runtime_wakeup_cb)(void*);

macos/Sources/Ghostty/SurfaceView.swift

@@ -291,8 +291,6 @@ extension Ghostty {
     /// The configuration for a surface. For any configuration not set, defaults will be chosen from
     /// libghostty, usually from the Ghostty configuration.
     struct SurfaceConfiguration {
-        var kind: ghostty_surface_kind_e? = nil;
-
         /// Explicit font size to use in points
         var fontSize: Float32? = nil
         
@@ -305,7 +303,6 @@ extension Ghostty {
         init() {}
         
         init(from config: ghostty_surface_config_s) {
-            self.kind = config.kind;
             self.fontSize = config.font_size
             self.workingDirectory = String.init(cString: config.working_directory, encoding: .utf8)
             self.command = String.init(cString: config.command, encoding: .utf8)
@@ -337,7 +334,6 @@ extension Ghostty {
             #error("unsupported target")
             #endif
             
-            if let kind = kind { config.kind = kind }
             if let fontSize = fontSize { config.font_size = fontSize }
             if let workingDirectory = workingDirectory {
                 config.working_directory = (workingDirectory as NSString).utf8String

src/Surface.zig

@@ -126,7 +126,7 @@ config: DerivedConfig,
 child_exited: bool = false,
 
 /// The kind of surface.
-pub const Kind = enum(c_int) {
+pub const Kind = enum {
     split,
     tab,
     window,

src/apprt/embedded.zig

@@ -8,6 +8,7 @@ const std = @import("std");
 const builtin = @import("builtin");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
+const ArenaAllocator = std.heap.ArenaAllocator;
 const objc = @import("objc");
 const apprt = @import("../apprt.zig");
 const font = @import("../font/main.zig");
@@ -308,9 +309,6 @@ pub const Surface = struct {
 
     /// Surface initialization options.
     pub const Options = extern struct {
-        /// The initial kind of surface.
-        kind: CoreSurface.Kind = .window,
-
         /// The platform that this surface is being initialized for and
         /// the associated platform-specific configuration.
         platform_tag: c_int = 0,
@@ -332,6 +330,17 @@ pub const Surface = struct {
         /// the "wait-after-command" option is also automatically set to true,
         /// since this is used for scripting.
         command: [*:0]const u8 = "",
+
+        _arena: ?*anyopaque = null,
+
+        pub fn deinit(self: *Options) void {
+            if (self._arena) |ptr| {
+                const arena: *ArenaAllocator = @ptrCast(@alignCast(ptr));
+                const alloc = arena.child_allocator;
+                arena.deinit();
+                alloc.destroy(arena);
+            }
+        }
     };
 
     /// This is the key event sent for ghostty_surface_key.
@@ -368,7 +377,7 @@ pub const Surface = struct {
         errdefer app.core_app.deleteSurface(self);
 
         // Shallow copy the config so that we can modify it.
-        var config = try apprt.surface.newConfig(app.core_app, app.config, opts.kind);
+        var config = try apprt.surface.newConfig(app.core_app, app.config);
         defer config.deinit();
 
         // If we have a working directory from the options then we set it.
@@ -476,7 +485,7 @@ pub const Surface = struct {
             return;
         };
 
-        const options = self.newSurfaceOptions(.split);
+        const options = try self.newSurfaceOptions(.split);
         func(self.userdata, direction, options);
     }
 
@@ -1027,7 +1036,7 @@ pub const Surface = struct {
             return;
         };
 
-        const options = self.newSurfaceOptions(.tab);
+        const options = try self.newSurfaceOptions(.tab);
         func(self.userdata, options);
     }
 
@@ -1037,7 +1046,7 @@ pub const Surface = struct {
             return;
         };
 
-        const options = self.newSurfaceOptions(.window);
+        const options = try self.newSurfaceOptions(.window);
         func(self.userdata, options);
     }
 
@@ -1068,15 +1077,44 @@ pub const Surface = struct {
         func(self.userdata, width, height);
     }
 
-    fn newSurfaceOptions(self: *const Surface, kind: CoreSurface.Kind) apprt.Surface.Options {
+    fn newSurfaceOptions(self: *const Surface, kind: CoreSurface.Kind) !apprt.Surface.Options {
         const font_size: f32 = font_size: {
             if (!self.app.config.@"window-inherit-font-size") break :font_size 0;
             break :font_size self.core_surface.font_size.points;
         };
 
+        const working_directory: [*:0]const u8, const arena: ?*ArenaAllocator = dir: {
+            const prev = self.app.core_app.focusedSurface();
+            if (prev) |p| {
+                const inherit_pwd: bool = switch (kind) {
+                    .split => self.app.config.@"window-inherit-working-directory".split,
+                    .tab => self.app.config.@"window-inherit-working-directory".tab,
+                    .window => self.app.config.@"window-inherit-working-directory".window,
+                };
+                if (inherit_pwd) {
+                    const app_alloc = self.app.core_app.alloc;
+
+                    var arena = try app_alloc.create(ArenaAllocator);
+                    errdefer app_alloc.destroy(arena);
+
+                    arena.* = ArenaAllocator.init(app_alloc);
+                    errdefer arena.deinit();
+
+                    const arena_alloc = arena.allocator();
+
+                    if (try p.pwd(app_alloc)) |pwd| {
+                        defer app_alloc.free(pwd);
+                        break :dir .{ try arena_alloc.dupeZ(u8, pwd), arena };
+                    }
+                }
+            }
+            break :dir .{ "", null };
+        };
+
         return .{
-            .kind = kind,
             .font_size = font_size,
+            .working_directory = working_directory,
+            ._arena = arena,
         };
     }
 
@@ -1503,6 +1541,7 @@ pub const CAPI = struct {
         app: *App,
         opts: *const apprt.Surface.Options,
     ) !*Surface {
+        defer @constCast(opts).deinit();
         return try app.newSurface(opts.*);
     }
 

src/apprt/glfw.zig

@@ -448,8 +448,7 @@ pub const Surface = struct {
         errdefer app.app.deleteSurface(self);
 
         // Get our new surface config
-        const kind: CoreSurface.Kind = .window; // TODO
-        var config = try apprt.surface.newConfig(app.app, &app.config, kind);
+        var config = try apprt.surface.newConfig(app.app, &app.config);
         defer config.deinit();
 
         // Initialize our surface now that we have the stable pointer.

src/apprt/gtk/Surface.zig

@@ -543,8 +543,7 @@ fn realize(self: *Surface) !void {
     errdefer self.app.core_app.deleteSurface(self);
 
     // Get our new surface config
-    const kind: CoreSurface.Kind = .window; // TODO
-    var config = try apprt.surface.newConfig(self.app.core_app, &self.app.config, kind);
+    var config = try apprt.surface.newConfig(self.app.core_app, &self.app.config);
     defer config.deinit();
     if (!self.parent_surface) {
         // A hack, see the "parent_surface" field for more information.

src/apprt/surface.zig

@@ -1,4 +1,3 @@
-const std = @import("std");
 const apprt = @import("../apprt.zig");
 const App = @import("../App.zig");
 const Surface = @import("../Surface.zig");
@@ -86,27 +85,7 @@ pub const Mailbox = struct {
 /// Returns a new config for a surface for the given app that should be
 /// used for any new surfaces. The resulting config should be deinitialized
 /// after the surface is initialized.
-pub fn newConfig(app: *const App, config: *const Config, kind: Surface.Kind) !Config {
+pub fn newConfig(app: *const App, config: *const Config) !Config {
     // Create a shallow clone
-    var copy = config.shallowClone(app.alloc);
-
-    // Our allocator is our config's arena
-    const alloc = copy._arena.?.allocator();
-
-    // Get our previously focused surface for some inherited values.
-    const prev = app.focusedSurface();
-    if (prev) |p| {
-        const inherit_pwd: bool = switch (kind) {
-            .split => config.@"window-inherit-working-directory".split,
-            .tab => config.@"window-inherit-working-directory".tab,
-            .window => config.@"window-inherit-working-directory".window,
-        };
-        if (inherit_pwd) {
-            if (try p.pwd(alloc)) |pwd| {
-                copy.@"working-directory" = pwd;
-            }
-        }
-    }
-
-    return copy;
+    return config.shallowClone(app.alloc);
 }