gtk(bell): add `bell-features` config option

Co-authored-by: Jeffrey C. Ollie <jeff@ocjtech.us>

src/apprt/gtk/Surface.zig

@@ -2441,13 +2441,15 @@ pub fn setSecureInput(self: *Surface, value: apprt.action.SecureInput) void {
 }
 
 pub fn ringBell(self: *Surface) !void {
+    const features = self.app.config.@"bell-features";
     const window = self.container.window() orelse {
         log.warn("failed to ring bell: surface is not attached to any window", .{});
         return;
     };
 
     // System beep
-    if (window.window.as(gtk.Native).getSurface()) |surface| {
+    if (features.system) system: {
+        const surface = window.window.as(gtk.Native).getSurface() orelse break :system;
         surface.beep();
     }
 

src/config/Config.zig

@@ -1848,6 +1848,22 @@ keybind: Keybinds = .{},
 /// open terminals.
 @"custom-shader-animation": CustomShaderAnimation = .true,
 
+/// The list of enabled features that are activated after encountering
+/// a bell character.
+///
+/// Valid values are:
+///
+///  * `system` (default)
+///
+///    Instructs the system to notify the user using built-in system functions.
+///    This could result in an audiovisual effect, a notification, or something
+///    else entirely. Changing these effects require altering system settings:
+///    for instance under the "Sound > Alert Sound" setting in GNOME,
+///    or the "Accessibility > System Bell" settings in KDE Plasma.
+///
+/// Currently only implemented on Linux.
+@"bell-features": BellFeatures = .{},
+
 /// Control the in-app notifications that Ghostty shows.
 ///
 /// On Linux (GTK), in-app notifications show up as toasts. Toasts appear
@@ -5669,6 +5685,11 @@ pub const AppNotifications = packed struct {
     @"clipboard-copy": bool = true,
 };
 
+/// See bell-features
+pub const BellFeatures = packed struct {
+    system: bool = false,
+};
+
 /// See mouse-shift-capture
 pub const MouseShiftCapture = enum {
     false,