Merge pull request #222 from mitchellh/size

only send resize messages to renderer/io thread if changes happen

src/Surface.zig

@@ -444,8 +444,8 @@ pub fn init(
         .io = io,
         .io_thread = io_thread,
         .io_thr = undefined,
-        .screen_size = screen_size,
+        .screen_size = .{ .width = 0, .height = 0 },
-        .grid_size = grid_size,
+        .grid_size = .{},
         .cell_size = cell_size,
         .padding = padding,
         .config = try DerivedConfig.init(alloc, config),
@@ -827,20 +827,35 @@ pub fn sizeCallback(self: *Surface, size: apprt.SurfaceSize) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    // TODO: if our screen size didn't change, then we should avoid the
+    const new_screen_size: renderer.ScreenSize = .{
-    // overhead of inter-thread communication
-
-    // Save our screen size
-    self.screen_size = .{
         .width = size.width,
         .height = size.height,
     };
 
-    // Recalculate our grid size
+    // Update our screen size, but only if it actually changed. And if
-    self.grid_size = renderer.GridSize.init(
+    // the screen size didn't change, then our grid size could not have
+    // changed, so we just return.
+    if (self.screen_size.equals(new_screen_size)) return;
+
+    // Save our screen size
+    self.screen_size = new_screen_size;
+
+    // Mail the renderer so that it can update the GPU and re-render
+    _ = self.renderer_thread.mailbox.push(.{
+        .screen_size = self.screen_size,
+    }, .{ .forever = {} });
+    try self.queueRender();
+
+    // Recalculate our grid size. Because Ghostty supports fluid resizing,
+    // its possible the grid doesn't change at all even if the screen size changes.
+    const new_grid_size = renderer.GridSize.init(
         self.screen_size.subPadding(self.padding),
         self.cell_size,
     );
+    if (self.grid_size.equals(new_grid_size)) return;
+
+    // Grid size changed, update our grid size and notify the terminal
+    self.grid_size = new_grid_size;
     if (self.grid_size.columns < 5 and (self.padding.left > 0 or self.padding.right > 0)) {
         log.warn("WARNING: very small terminal grid detected with padding " ++
             "set. Is your padding reasonable?", .{});
@@ -850,12 +865,6 @@ pub fn sizeCallback(self: *Surface, size: apprt.SurfaceSize) !void {
             "set. Is your padding reasonable?", .{});
     }
 
-    // Mail the renderer
-    _ = self.renderer_thread.mailbox.push(.{
-        .screen_size = self.screen_size,
-    }, .{ .forever = {} });
-    try self.queueRender();
-
     // Mail the IO thread
     _ = self.io_thread.mailbox.push(.{
         .resize = .{

src/renderer/size.zig

@@ -52,6 +52,11 @@ pub const ScreenSize = struct {
             .height = self.height -| (padding.top + padding.bottom),
         };
     }
+
+    /// Returns true if two sizes are equal.
+    pub fn equals(self: ScreenSize, other: ScreenSize) bool {
+        return self.width == other.width and self.height == other.height;
+    }
 };
 
 /// The dimensions of the grid itself, in rows/columns units.
@@ -80,6 +85,11 @@ pub const GridSize = struct {
         self.columns = @max(1, calc_cols);
         self.rows = @max(1, calc_rows);
     }
+
+    /// Returns true if two sizes are equal.
+    pub fn equals(self: GridSize, other: GridSize) bool {
+        return self.columns == other.columns and self.rows == other.rows;
+    }
 };
 
 /// The padding to add to a screen.