gtk(wayland): implement server-side decorations

src/apprt/gtk/Window.zig

@@ -157,9 +157,6 @@ pub fn init(self: *Window, app: *App) !void {
     if (app.config.@"gtk-titlebar") {
         const header = HeaderBar.init(self);
 
-        // If we are not decorated then we hide the titlebar.
-        header.setVisible(app.config.@"window-decoration");
-
         {
             const btn = c.gtk_menu_button_new();
             c.gtk_widget_set_tooltip_text(btn, "Main Menu");
@@ -212,11 +209,6 @@ pub fn init(self: *Window, app: *App) !void {
 
     _ = c.g_signal_connect_data(gtk_window, "notify::decorated", c.G_CALLBACK(&gtkWindowNotifyDecorated), self, null, c.G_CONNECT_DEFAULT);
 
-    // If we are disabling decorations then disable them right away.
-    if (!app.config.@"window-decoration") {
-        c.gtk_window_set_decorated(gtk_window, 0);
-    }
-
     // If Adwaita is enabled and is older than 1.4.0 we don't have the tab overview and so we
     // need to stick the headerbar into the content box.
     if (!adwaita.versionAtLeast(1, 4, 0) and adwaita.enabled(&self.app.config)) {
@@ -390,14 +382,40 @@ pub fn init(self: *Window, app: *App) !void {
 /// TODO: Many of the initial style settings in `create` could possibly be made
 /// reactive by moving them here.
 pub fn syncAppearance(self: *Window, config: *const configpkg.Config) !void {
-    if (config.@"background-opacity" < 1) {
-        c.gtk_widget_remove_css_class(@ptrCast(self.window), "background");
-    } else {
-        c.gtk_widget_add_css_class(@ptrCast(self.window), "background");
-    }
-
     // Perform protocol-specific config updates
     try self.protocol.onConfigUpdate(config);
+
+    toggleCssClass(
+        @ptrCast(self.window),
+        "background",
+        config.@"background-opacity" >= 1,
+    );
+
+    // If we are disabling CSDs then disable them right away.
+    const csd_enabled = self.protocol.clientSideDecorationEnabled();
+    c.gtk_window_set_decorated(self.window, @intFromBool(csd_enabled));
+
+    // If we are not decorated then we hide the titlebar.
+    if (self.header) |header| {
+        header.setVisible(config.@"gtk-titlebar" and csd_enabled);
+    }
+
+    // Disable the title buttons (close, maximize, minimize, ...)
+    // *inside* the tab overview if CSDs are disabled.
+    // We do spare the search button, though.
+    // (...Why the heck is there a header bar inside the tab overview to begin with??)
+    if (self.tab_overview) |tab_overview| {
+        c.adw_tab_overview_set_show_start_title_buttons(@ptrCast(tab_overview), @intFromBool(csd_enabled));
+        c.adw_tab_overview_set_show_end_title_buttons(@ptrCast(tab_overview), @intFromBool(csd_enabled));
+    }
+}
+
+fn toggleCssClass(widget: *c.GtkWidget, class: [:0]const u8, v: bool) void {
+    if (v) {
+        c.gtk_widget_add_css_class(widget, class);
+    } else {
+        c.gtk_widget_remove_css_class(widget, class);
+    }
 }
 
 /// Sets up the GTK actions for the window scope. Actions are how GTK handles
@@ -526,17 +544,12 @@ pub fn toggleFullscreen(self: *Window) void {
 
 /// Toggle the window decorations for this window.
 pub fn toggleWindowDecorations(self: *Window) void {
-    const old_decorated = c.gtk_window_get_decorated(self.window) == 1;
-    const new_decorated = !old_decorated;
-    c.gtk_window_set_decorated(self.window, @intFromBool(new_decorated));
-
-    // If we have a titlebar, then we also show/hide it depending on the
-    // decorated state. GTK tends to consider the titlebar part of the frame
-    // and hides it with decorations, but libadwaita doesn't. This makes it
-    // explicit.
-    if (self.header) |headerbar| {
-        headerbar.setVisible(new_decorated);
-    }
+    self.app.config.@"window-decoration" = switch (self.app.config.@"window-decoration") {
+        .true => .server,
+        .server => .false,
+        .false => .true,
+    };
+    self.syncAppearance(&self.app.config) catch {};
 }
 
 /// Grabs focus on the currently selected tab.
@@ -576,17 +589,14 @@ fn gtkWindowNotifyDecorated(
     _: *c.GParamSpec,
     _: ?*anyopaque,
 ) callconv(.C) void {
-    if (c.gtk_window_get_decorated(@ptrCast(object)) == 1) {
-        c.gtk_widget_remove_css_class(@ptrCast(object), "ssd");
-        c.gtk_widget_remove_css_class(@ptrCast(object), "no-border-radius");
-    } else {
-        // Fix any artifacting that may occur in window corners. The .ssd CSS
-        // class is defined in the GtkWindow documentation:
-        // https://docs.gtk.org/gtk4/class.Window.html#css-nodes. A definition
-        // for .ssd is provided by GTK and Adwaita.
-        c.gtk_widget_add_css_class(@ptrCast(object), "ssd");
-        c.gtk_widget_add_css_class(@ptrCast(object), "no-border-radius");
-    }
+    const is_decorated = c.gtk_window_get_decorated(@ptrCast(object)) == 1;
+
+    // Fix any artifacting that may occur in window corners. The .ssd CSS
+    // class is defined in the GtkWindow documentation:
+    // https://docs.gtk.org/gtk4/class.Window.html#css-nodes. A definition
+    // for .ssd is provided by GTK and Adwaita.
+    toggleCssClass(@ptrCast(object), "ssd", !is_decorated);
+    toggleCssClass(@ptrCast(object), "no-border-radius", !is_decorated);
 }
 
 // Note: we MUST NOT use the GtkButton parameter because gtkActionNewTab

src/apprt/gtk/protocol.zig

@@ -99,11 +99,13 @@ pub const Surface = struct {
     pub const DerivedConfig = struct {
         blur: Config.BackgroundBlur,
         adw_enabled: bool,
+        window_decoration: Config.WindowDecoration,
 
         pub fn init(config: *const Config) DerivedConfig {
             return .{
                 .blur = config.@"background-blur-radius",
                 .adw_enabled = adwaita.enabled(config),
+                .window_decoration = config.@"window-decoration",
             };
         }
     };
@@ -130,6 +132,17 @@ pub const Surface = struct {
         }
     }
 
+    pub fn clientSideDecorationEnabled(self: Surface) bool {
+        return switch (self.inner) {
+            // We can't do SSD anyway if the compositor doesn't support it
+            .wayland => |wl| if (comptime build_options.x11)
+                self.derived_config.window_decoration == .true or wl.decoration == null
+            else
+                unreachable,
+            .x11, .none => self.derived_config.window_decoration != .false,
+        };
+    }
+
     pub fn onConfigUpdate(self: *Surface, config: *const Config) !void {
         self.derived_config = DerivedConfig.init(config);
 

src/apprt/gtk/protocol/wayland.zig

@@ -12,7 +12,10 @@ const log = std.log.scoped(.gtk_wayland);
 /// Wayland state that contains application-wide Wayland objects (e.g. wl_display).
 pub const App = struct {
     display: *wl.Display,
+
     blur_manager: ?*org.KdeKwinBlurManager = null,
+    // FIXME: replace with `zxdg_decoration_v1` once GTK merges https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/6398
+    decoration_manager: ?*org.KdeKwinServerDecorationManager = null,
 
     pub fn init(common: *protocol.App) !void {
         // Check if we're actually on Wayland
@@ -45,6 +48,7 @@ pub const Surface = struct {
 
     /// A token that, when present, indicates that the window is blurred.
     blur_token: ?*org.KdeKwinBlur = null,
+    decoration: ?*org.KdeKwinServerDecoration = null,
 
     pub fn init(common: *protocol.Surface) void {
         const surface = c.gtk_native_get_surface(@ptrCast(common.gtk_window)) orelse return;
@@ -56,21 +60,31 @@ pub const Surface = struct {
         ) == 0)
             return;
 
-        const self: Surface = .{
+        var self: Surface = .{
             .common = common,
             .app = &common.app.inner.wayland,
             .surface = @ptrCast(c.gdk_wayland_surface_get_wl_surface(surface) orelse return),
         };
 
+        if (self.app.decoration_manager) |mgr| {
+            if (mgr.create(self.surface)) |deco| {
+                self.decoration = deco;
+            } else |err| {
+                log.warn("could not create decoration object={}", .{err});
+            }
+        }
+
         common.inner = .{ .wayland = self };
     }
 
     pub fn deinit(self: Surface) void {
         if (self.blur_token) |blur| blur.release();
+        if (self.decoration) |deco| deco.release();
     }
 
     pub fn onConfigUpdate(self: *Surface) !void {
         try self.updateBlur();
+        try self.updateDecoration();
     }
 
     fn updateBlur(self: *Surface) !void {
@@ -98,6 +112,18 @@ pub const Surface = struct {
             }
         }
     }
+
+    fn updateDecoration(self: *Surface) !void {
+        if (self.decoration) |deco| {
+            const mode: org.KdeKwinServerDecoration.Mode = switch (self.common.derived_config.window_decoration) {
+                .true => .Client,
+                .server => .Server,
+                .false => .None,
+            };
+
+            deco.requestMode(@intCast(@intFromEnum(mode)));
+        }
+    }
 };
 
 fn registryListener(registry: *wl.Registry, event: wl.Registry.Event, state: *App) void {
@@ -108,6 +134,10 @@ fn registryListener(registry: *wl.Registry, event: wl.Registry.Event, state: *Ap
                 state.blur_manager = iface;
                 return;
             }
+            if (bindInterface(org.KdeKwinServerDecorationManager, registry, global, 1)) |iface| {
+                state.decoration_manager = iface;
+                return;
+            }
         },
         .global_remove => {},
     }

src/build/SharedDeps.zig

@@ -452,10 +452,14 @@ pub fn add(
                         .target = target,
                         .optimize = optimize,
                     });
+
+                    // FIXME: replace with `zxdg_decoration_v1` once GTK merges https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/6398
                     scanner.addCustomProtocol(plasma_wayland_protocols.path("src/protocols/blur.xml"));
+                    scanner.addCustomProtocol(plasma_wayland_protocols.path("src/protocols/server-decoration.xml"));
 
                     scanner.generate("wl_compositor", 1);
                     scanner.generate("org_kde_kwin_blur_manager", 1);
+                    scanner.generate("org_kde_kwin_server_decoration_manager", 1);
 
                     step.root_module.addImport("wayland", wayland);
                     step.linkSystemLibrary2("wayland-client", dynamic_link_opts);

src/config/Config.zig

@@ -1110,7 +1110,7 @@ keybind: Keybinds = .{},
 ///
 /// macOS: To hide the titlebar without removing the native window borders
 ///        or rounded corners, use `macos-titlebar-style = hidden` instead.
-@"window-decoration": bool = true,
+@"window-decoration": WindowDecoration = .true,
 
 /// The font that will be used for the application's window and tab titles.
 ///
@@ -5780,6 +5780,27 @@ pub const BackgroundBlur = union(enum) {
     }
 };
 
+/// See window-decoration
+pub const WindowDecoration = enum {
+    true,
+    server,
+    false,
+
+    pub fn parseCLI(input: ?[]const u8) !WindowDecoration {
+        const input_ = input orelse {
+            // Emulate behavior for bools
+            return .true;
+        };
+
+        return if (cli.args.parseBool(input_)) |b|
+            if (b) .true else .false
+        else |_| if (std.mem.eql(u8, input_, "server"))
+            .server
+        else
+            error.InvalidValue;
+    }
+};
+
 /// See theme
 pub const Theme = struct {
     light: []const u8,