fix(renderer): rebuild font grid and reset shaper cache on hot reload

When hot reloading config with a new font, shaper cache data needs to be
invalidated and the font grid needs to be rebuilt. This change just
makes that happen on all config reloads since it's a rare action so it's
not a performance concern.

src/Surface.zig

@@ -757,6 +757,13 @@ fn changeConfig(self: *Surface, config: *const configpkg.Config) !void {
         self.showMouse();
     }
 
+    // Before sending any other config changes, we give the renderer a new font
+    // grid. We could check to see if there was an actual change to the font,
+    // but this is easier and pretty rare so it's not a performance concern.
+    //
+    // (Calling setFontSize builds and sends a new font grid to the renderer.)
+    try self.setFontSize(self.font_size);
+
     // We need to store our configs in a heap-allocated pointer so that
     // our messages aren't huge.
     var renderer_message = try renderer.Message.initChangeConfig(self.alloc, config);

src/renderer/Metal.zig

@@ -783,7 +783,7 @@ pub fn setVisible(self: *Metal, visible: bool) void {
     }
 }
 
-/// Set the new font size.
+/// Set the new font grid.
 ///
 /// Must be called on the render thread.
 pub fn setFontGrid(self: *Metal, grid: *font.SharedGrid) void {
@@ -812,6 +812,13 @@ pub fn setFontGrid(self: *Metal, grid: *font.SharedGrid) void {
         log.err("error resizing cells buffer err={}", .{err});
     };
 
+    // Reset our shaper cache. If our font changed (not just the size) then
+    // the data in the shaper cache may be invalid and cannot be used, so we
+    // always clear the cache just in case.
+    const font_shaper_cache = font.ShaperCache.init();
+    self.font_shaper_cache.deinit(self.alloc);
+    self.font_shaper_cache = font_shaper_cache;
+
     // Reset our viewport to force a rebuild
     self.cells_viewport = null;
 
@@ -1726,6 +1733,12 @@ pub fn changeConfig(self: *Metal, config: *DerivedConfig) !void {
         self.font_shaper = font_shaper;
     }
 
+    // We also need to reset the shaper cache so shaper info
+    // from the previous font isn't re-used for the new font.
+    const font_shaper_cache = font.ShaperCache.init();
+    self.font_shaper_cache.deinit(self.alloc);
+    self.font_shaper_cache = font_shaper_cache;
+
     // Set our new minimum contrast
     self.uniforms.min_contrast = config.min_contrast;
 
@@ -1736,6 +1749,9 @@ pub fn changeConfig(self: *Metal, config: *DerivedConfig) !void {
 
     self.config.deinit();
     self.config = config.*;
+
+    // Reset our viewport to force a rebuild, in case of a font change.
+    self.cells_viewport = null;
 }
 
 /// Resize the screen.

src/renderer/OpenGL.zig

@@ -595,7 +595,7 @@ pub fn setVisible(self: *OpenGL, visible: bool) void {
     _ = visible;
 }
 
-/// Set the new font size.
+/// Set the new font grid.
 ///
 /// Must be called on the render thread.
 pub fn setFontGrid(self: *OpenGL, grid: *font.SharedGrid) void {
@@ -610,6 +610,13 @@ pub fn setFontGrid(self: *OpenGL, grid: *font.SharedGrid) void {
     self.texture_color_modified = 0;
     self.texture_color_resized = 0;
 
+    // Reset our shaper cache. If our font changed (not just the size) then
+    // the data in the shaper cache may be invalid and cannot be used, so we
+    // always clear the cache just in case.
+    const font_shaper_cache = font.ShaperCache.init();
+    self.font_shaper_cache.deinit(self.alloc);
+    self.font_shaper_cache = font_shaper_cache;
+
     // Defer our GPU updates
     self.deferred_font_size = .{ .metrics = grid.metrics };
 }
@@ -1577,6 +1584,12 @@ pub fn changeConfig(self: *OpenGL, config: *DerivedConfig) !void {
         self.font_shaper = font_shaper;
     }
 
+    // We also need to reset the shaper cache so shaper info
+    // from the previous font isn't re-used for the new font.
+    const font_shaper_cache = font.ShaperCache.init();
+    self.font_shaper_cache.deinit(self.alloc);
+    self.font_shaper_cache = font_shaper_cache;
+
     // Set our new colors
     self.background_color = config.background;
     self.foreground_color = config.foreground;