pass around the event loop, setup a timer to prove it works

src/App.zig

@@ -18,21 +18,30 @@ alloc: Allocator,
 /// single window operations.
 window: *Window,
 
-// The main event loop for the application.
+// The main event loop for the application. The user data of this loop
+// is always the allocator used to create the loop. This is a convenience
+// so that users of the loop always have an allocator.
 loop: libuv.Loop,
 
 /// 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 init(alloc: Allocator) !App {
-    // Create the window
-    var window = try Window.create(alloc);
-    errdefer window.destroy();
-
     // Create the event loop
     var loop = try libuv.Loop.init(alloc);
     errdefer loop.deinit(alloc);
 
+    // We always store allocator pointer on the loop data so that
+    // handles can use our global allocator.
+    const allocPtr = try alloc.create(Allocator);
+    errdefer alloc.destroy(allocPtr);
+    allocPtr.* = alloc;
+    loop.setData(allocPtr);
+
+    // Create the window
+    var window = try Window.create(alloc, loop);
+    errdefer window.destroy();
+
     return App{
         .alloc = alloc,
         .window = window,
@@ -42,6 +51,15 @@ pub fn init(alloc: Allocator) !App {
 
 pub fn deinit(self: *App) void {
     self.window.destroy();
+
+    // Run the loop one more time, because destroying our other things
+    // like windows usually cancel all our event loop stuff and we need
+    // one more run through to finalize all the closes.
+    _ = self.loop.run(.default) catch unreachable;
+
+    // Dealloc our allocator copy
+    self.alloc.destroy(self.loop.getData(Allocator).?);
+
     self.loop.deinit(self.alloc);
     self.* = undefined;
 }

src/Grid.zig

@@ -10,6 +10,7 @@ const FontAtlas = @import("FontAtlas.zig");
 const Terminal = @import("terminal/Terminal.zig");
 const gl = @import("opengl.zig");
 const gb = @import("gb_math.zig");
+const libuv = @import("libuv/main.zig");
 
 const log = std.log.scoped(.grid);
 
@@ -34,6 +35,9 @@ texture: gl.Texture,
 /// The font atlas.
 font_atlas: FontAtlas,
 
+/// The timer for cursor blining.
+cursor_timer: libuv.Timer,
+
 /// The raw structure that maps directly to the buffer sent to the vertex shader.
 const GPUCell = struct {
     /// vec2 grid_coord
@@ -68,7 +72,11 @@ const GPUCell = struct {
     mode: u8,
 };
 
-pub fn init(alloc: Allocator) !Grid {
+pub fn init(alloc: Allocator, loop: libuv.Loop) !Grid {
+    // Setup the timer for our cursor.
+    var timer = try libuv.Timer.init(alloc, loop);
+    errdefer timer.deinit(alloc);
+
     // Initialize our font atlas. We will initially populate the
     // font atlas with all the visible ASCII characters since they are common.
     var atlas = try Atlas.init(alloc, 512);
@@ -206,10 +214,17 @@ pub fn init(alloc: Allocator) !Grid {
         .vbo = vbo,
         .texture = tex,
         .font_atlas = font,
+        .cursor_timer = timer,
     };
 }
 
 pub fn deinit(self: *Grid) void {
+    self.cursor_timer.close((struct {
+        fn callback(t: *libuv.Timer) void {
+            const alloc = t.loop().getData(Allocator).?;
+            t.deinit(alloc.*);
+        }
+    }).callback);
     self.font_atlas.atlas.deinit(self.alloc);
     self.font_atlas.deinit(self.alloc);
     self.texture.destroy();

src/Window.zig

@@ -11,6 +11,7 @@ const Allocator = std.mem.Allocator;
 const Grid = @import("Grid.zig");
 const glfw = @import("glfw");
 const gl = @import("opengl.zig");
+const libuv = @import("libuv/main.zig");
 const Pty = @import("Pty.zig");
 const Terminal = @import("terminal/Terminal.zig");
 
@@ -37,7 +38,7 @@ terminal: Terminal,
 /// 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(alloc: Allocator) !*Window {
+pub fn create(alloc: Allocator, loop: libuv.Loop) !*Window {
     var self = try alloc.create(Window);
     errdefer alloc.destroy(self);
 
@@ -77,7 +78,7 @@ pub fn create(alloc: Allocator) !*Window {
 
     // Create our terminal grid with the initial window size
     const window_size = try window.getSize();
-    var grid = try Grid.init(alloc);
+    var grid = try Grid.init(alloc, loop);
     try grid.setScreenSize(.{ .width = window_size.width, .height = window_size.height });
 
     // Create our pty

src/libuv/Loop.zig

@@ -70,6 +70,19 @@ pub fn backendTimeout(self: Loop) c_int {
     return c.uv_backend_timeout(self.loop);
 }
 
+/// Sets loop->data to data.
+pub fn setData(self: Loop, pointer: ?*anyopaque) void {
+    c.uv_loop_set_data(self.loop, pointer);
+}
+
+/// Returns loop->data.
+pub fn getData(self: Loop, comptime DT: type) ?*DT {
+    return if (c.uv_loop_get_data(self.loop)) |ptr|
+        @ptrCast(?*DT, @alignCast(@alignOf(DT), ptr))
+    else
+        null;
+}
+
 /// Mode used to run the loop with uv_run().
 pub const RunMode = enum(c.uv_run_mode) {
     default = c.UV_RUN_DEFAULT,
@@ -81,6 +94,10 @@ test {
     var loop = try init(testing.allocator);
     defer loop.deinit(testing.allocator);
 
+    var data: u8 = 42;
+    loop.setData(&data);
+    try testing.expect(loop.getData(u8).?.* == 42);
+
     try testing.expect((try loop.backendFd()) > 0);
     try testing.expectEqual(@as(u32, 0), try loop.run(.nowait));
 }

src/libuv/Timer.zig

@@ -85,7 +85,7 @@ test "Timer: close callback" {
     var data: u8 = 42;
     timer.setData(&data);
     timer.close((struct {
-        fn callback(v: Timer) void {
+        fn callback(v: *Timer) void {
             var dataPtr = v.getData(u8).?;
             dataPtr.* = 24;
         }

src/libuv/handle.zig

@@ -27,15 +27,15 @@ pub fn Handle(comptime T: type) type {
         //
         // In-progress requests, like uv_connect_t or uv_write_t, are cancelled
         // and have their callbacks called asynchronously with status=UV_ECANCELED.
-        pub fn close(self: T, comptime cb: ?fn (T) void) void {
+        pub fn close(self: T, comptime cb: ?fn (*T) void) void {
             const cbParam = if (cb) |f|
                 (struct {
                     pub fn callback(handle: [*c]c.uv_handle_t) callconv(.C) void {
                         // We get the raw handle, so we need to reconstruct
                         // the T. This is mutable because a lot of the libuv APIs
                         // are non-const but modifying it makes no sense.
-                        const param: T = .{ .handle = @ptrCast(HandleType, handle) };
-                        @call(.{ .modifier = .always_inline }, f, .{param});
+                        var param: T = .{ .handle = @ptrCast(HandleType, handle) };
+                        @call(.{ .modifier = .always_inline }, f, .{&param});
                     }
                 }).callback
             else