apprt/gtk: add toggle_background_opacity option

include/ghostty.h

@@ -570,6 +570,7 @@ typedef enum {
   GHOSTTY_ACTION_TOGGLE_FULLSCREEN,
   GHOSTTY_ACTION_TOGGLE_TAB_OVERVIEW,
   GHOSTTY_ACTION_TOGGLE_WINDOW_DECORATIONS,
+  GHOSTTY_ACTION_TOGGLE_BACKGROUND_OPACITY,
   GHOSTTY_ACTION_TOGGLE_QUICK_TERMINAL,
   GHOSTTY_ACTION_TOGGLE_VISIBILITY,
   GHOSTTY_ACTION_MOVE_TAB,

src/Surface.zig

@@ -4257,6 +4257,12 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !bool
             {},
         ),
 
+        .toggle_background_opacity => return try self.rt_app.performAction(
+            .{ .surface = self },
+            .toggle_background_opacity,
+            {},
+        ),
+
         .toggle_tab_overview => return try self.rt_app.performAction(
             .{ .surface = self },
             .toggle_tab_overview,

src/apprt/action.zig

@@ -104,6 +104,9 @@ pub const Action = union(Key) {
     /// Toggle whether window directions are shown.
     toggle_window_decorations,
 
+    /// Toggle the background opacity of the target terminal.
+    toggle_background_opacity,
+
     /// Toggle the quick terminal in or out.
     toggle_quick_terminal,
 
@@ -253,6 +256,7 @@ pub const Action = union(Key) {
         toggle_fullscreen,
         toggle_tab_overview,
         toggle_window_decorations,
+        toggle_background_opacity,
         toggle_quick_terminal,
         toggle_visibility,
         move_tab,

src/apprt/glfw.zig

@@ -222,6 +222,7 @@ pub const App = struct {
             .close_tab,
             .toggle_tab_overview,
             .toggle_window_decorations,
+            .toggle_background_opacity,
             .toggle_quick_terminal,
             .toggle_visibility,
             .goto_tab,

src/apprt/gtk/App.zig

@@ -499,6 +499,7 @@ pub fn performAction(
         .toggle_tab_overview => self.toggleTabOverview(target),
         .toggle_split_zoom => self.toggleSplitZoom(target),
         .toggle_window_decorations => self.toggleWindowDecorations(target),
+        .toggle_background_opacity => self.toggleBackgroundOpacity(target),
         .quit_timer => self.quitTimer(value),
         .prompt_title => try self.promptTitle(target),
         .toggle_quick_terminal => return try self.toggleQuickTerminal(),
@@ -796,6 +797,25 @@ fn toggleQuickTerminal(self: *App) !bool {
     return true;
 }
 
+fn toggleBackgroundOpacity(
+    _: *App,
+    target: apprt.Target,
+) void {
+    switch (target) {
+        .app => {},
+        .surface => |v| {
+            const window = v.rt_surface.container.window() orelse {
+                log.info(
+                    "toggleBackgroundOpacity invalid for container={s}",
+                    .{@tagName(v.rt_surface.container)},
+                );
+                return;
+            };
+            window.toggleBackgroundOpacity();
+        },
+    }
+}
+
 fn quitTimer(self: *App, mode: apprt.action.QuitTimer) void {
     switch (mode) {
         .start => self.startQuitTimer(),

src/apprt/gtk/Window.zig

@@ -661,6 +661,17 @@ pub fn toggleWindowDecorations(self: *Window) void {
     };
 }
 
+/// Toggle the background opacity for this window.
+pub fn toggleBackgroundOpacity(self: *Window) void {
+    if (self.app.config.@"background-opacity" >= 1) return;
+
+    if (c.gtk_widget_has_css_class(@ptrCast(self.window), "background") == 1) {
+        c.gtk_widget_remove_css_class(@ptrCast(self.window), "background");
+    } else {
+        c.gtk_widget_add_css_class(@ptrCast(self.window), "background");
+    }
+}
+
 /// Grabs focus on the currently selected tab.
 pub fn focusCurrentTab(self: *Window) void {
     const tab = self.notebook.currentTab() orelse return;

src/input/Binding.zig

@@ -431,6 +431,9 @@ pub const Action = union(enum) {
     /// Toggle window decorations on and off. This only works on Linux.
     toggle_window_decorations: void,
 
+    /// Toggle background opacity of window.
+    toggle_background_opacity: void,
+
     /// Toggle secure input mode on or off. This is used to prevent apps
     /// that monitor input from seeing what you type. This is useful for
     /// entering passwords or other sensitive information.
@@ -776,6 +779,7 @@ pub const Action = union(enum) {
             .toggle_maximize,
             .toggle_fullscreen,
             .toggle_window_decorations,
+            .toggle_background_opacity,
             .toggle_secure_input,
             .reset_window_size,
             .crash,