apprt/gtk: style gtk titlebar to match running terminal app

src/apprt/gtk/App.zig

@@ -473,6 +473,7 @@ pub fn performAction(
         .toggle_tab_overview => self.toggleTabOverview(target),
         .toggle_window_decorations => self.toggleWindowDecorations(target),
         .quit_timer => self.quitTimer(value),
+        .color_change => try self.colorChange(target, value),
 
         // Unimplemented
         .close_all_windows,
@@ -485,7 +486,6 @@ pub fn performAction(
         .key_sequence,
         .render_inspector,
         .renderer_health,
-        .color_change,
         => log.warn("unimplemented action={}", .{action}),
     }
 }
@@ -797,6 +797,17 @@ fn showDesktopNotification(
     c.g_application_send_notification(g_app, n.body.ptr, notification);
 }
 
+fn colorChange(
+    _: *App,
+    target: apprt.Target,
+    value: apprt.action.ColorChange,
+) !void {
+    switch (target) {
+        .app => {},
+        .surface => |v| try v.rt_surface.colorChange(value),
+    }
+}
+
 /// Reload the configuration. This should return the new configuration.
 /// The old value can be freed immediately at this point assuming a
 /// successful return.
@@ -898,6 +909,25 @@ fn loadRuntimeCss(
     alloc: Allocator,
     config: *const Config,
     provider: *c.GtkCssProvider,
+) Allocator.Error!void {
+    const headerbar_background = config.background;
+    const headerbar_foreground = config.foreground;
+
+    return loadRuntimeCssRGB(
+        alloc,
+        config,
+        provider,
+        headerbar_background,
+        headerbar_foreground,
+    );
+}
+
+fn loadRuntimeCssRGB(
+    alloc: Allocator,
+    config: *const Config,
+    provider: *c.GtkCssProvider,
+    background_color: Config.Color,
+    foreground_color: Config.Color,
 ) Allocator.Error!void {
     var stack_alloc = std.heap.stackFallback(4096, alloc);
     var buf = std.ArrayList(u8).init(stack_alloc.get());
@@ -906,8 +936,8 @@ fn loadRuntimeCss(
 
     const window_theme = config.@"window-theme";
     const unfocused_fill: Config.Color = config.@"unfocused-split-fill" orelse config.background;
-    const headerbar_background = config.background;
-    const headerbar_foreground = config.foreground;
+    const headerbar_background = background_color;
+    const headerbar_foreground = foreground_color;
 
     try writer.print(
         \\widget.unfocused-split {{
@@ -972,6 +1002,28 @@ fn loadRuntimeCss(
     );
 }
 
+/// Call this anytime the color scheme changes.
+pub fn syncColorChanges(
+    self: *App,
+    background_color: ?Config.Color,
+    foreground_color: ?Config.Color,
+) !void {
+    // Load our runtime CSS. If this fails then our window is just stuck
+    // with the old CSS but we don't want to fail the entire sync operation.
+    loadRuntimeCssRGB(
+        self.core_app.alloc,
+        &self.config,
+        self.css_provider,
+        background_color orelse self.config.background,
+        foreground_color orelse self.config.foreground,
+    ) catch |err| switch (err) {
+        error.OutOfMemory => log.warn(
+            "out of memory loading runtime CSS, no runtime CSS applied",
+            .{},
+        ),
+    };
+}
+
 /// Called by CoreApp to wake up the event loop.
 pub fn wakeup(self: App) void {
     _ = self;

src/apprt/gtk/Surface.zig

@@ -5,7 +5,7 @@ const Surface = @This();
 
 const std = @import("std");
 const Allocator = std.mem.Allocator;
-const configpkg = @import("../../config.zig");
+const Config = @import("../../config.zig").Config;
 const apprt = @import("../../apprt.zig");
 const font = @import("../../font/main.zig");
 const input = @import("../../input.zig");
@@ -342,6 +342,12 @@ cursor: ?*c.GdkCursor = null,
 /// pass it to GTK.
 title_text: ?[:0]const u8 = null,
 
+/// Local background color override.
+background_color: ?Config.Color = null,
+
+/// Local foreground color override.
+foreground_color: ?Config.Color = null,
+
 /// The core surface backing this surface
 core_surface: CoreSurface,
 
@@ -837,6 +843,32 @@ pub fn getTitle(self: *Surface) ?[:0]const u8 {
     return self.title_text;
 }
 
+fn updateStyle(self: *Surface) !void {
+    // If we have no style, then we have nothing to update.
+    if (self.background_color == null and self.foreground_color == null) return;
+
+    try self.app.syncColorChanges(self.background_color, self.foreground_color);
+}
+
+pub fn colorChange(self: *Surface, value: apprt.action.ColorChange) !void {
+    const color: Config.Color = .{
+        .r = value.r,
+        .g = value.g,
+        .b = value.b,
+    };
+    switch (value.kind) {
+        .background => {
+            self.background_color = color;
+            try self.updateStyle();
+        },
+        .foreground => {
+            self.foreground_color = color;
+            try self.updateStyle();
+        },
+        else => {},
+    }
+}
+
 pub fn setMouseShape(
     self: *Surface,
     shape: terminal.MouseShape,