gtk(wayland): implement server-sided decorations (#4724)

Fixes #4630 fully unless there exists an X11 API I haven't found yet :p 

~~Depends on first commit of #4723, which is duplicated here for now~~

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -165,11 +165,14 @@ extension Ghostty {
         }
 
         var windowDecorations: Bool {
-            guard let config = self.config else { return true }
-            var v = false;
+            let defaultValue = true
+            guard let config = self.config else { return defaultValue }
+            var v: UnsafePointer<Int8>? = nil
             let key = "window-decoration"
-            _ = ghostty_config_get(config, &v, key, UInt(key.count))
-            return v;
+            guard ghostty_config_get(config, &v, key, UInt(key.count)) else { return defaultValue }
+            guard let ptr = v else { return defaultValue }
+            let str = String(cString: ptr)
+            return WindowDecoration(rawValue: str)?.enabled() ?? defaultValue
         }
 
         var windowTheme: String? {
@@ -554,4 +557,17 @@ extension Ghostty.Config {
             }
         }
     }
+
+    enum WindowDecoration: String {
+        case none
+        case client
+        case server
+
+        func enabled() -> Bool {
+            switch self {
+            case .client, .server: return true
+            case .none: return false
+            }
+        }
+    }
 }

src/apprt/gtk/App.zig

@@ -1881,7 +1881,7 @@ fn initContextMenu(self: *App) void {
         c.g_menu_append(section, "Terminal Inspector", "win.toggle_inspector");
     }
 
-    if (!self.config.@"window-decoration") {
+    if (!self.config.@"window-decoration".isCSD()) {
         const section = c.g_menu_new();
         defer c.g_object_unref(section);
         const submenu = c.g_menu_new();

src/apprt/gtk/Surface.zig

@@ -1384,11 +1384,9 @@ fn gtkResize(area: *c.GtkGLArea, width: c.gint, height: c.gint, ud: ?*anyopaque)
         };
 
         if (self.container.window()) |window| {
-            if (window.winproto) |*winproto| {
-                winproto.resizeEvent() catch |err| {
-                    log.warn("failed to notify window protocol of resize={}", .{err});
-                };
-            }
+            window.winproto.resizeEvent() catch |err| {
+                log.warn("failed to notify window protocol of resize={}", .{err});
+            };
         }
 
         self.resize_overlay.maybeShow();

src/apprt/gtk/Window.zig

@@ -57,7 +57,7 @@ toast_overlay: ?*c.GtkWidget,
 adw_tab_overview_focus_timer: ?c.guint = null,
 
 /// State and logic for windowing protocol for a window.
-winproto: ?winproto.Window,
+winproto: winproto.Window,
 
 pub fn create(alloc: Allocator, app: *App) !*Window {
     // Allocate a fixed pointer for our window. We try to minimize
@@ -83,7 +83,7 @@ pub fn init(self: *Window, app: *App) !void {
         .notebook = undefined,
         .context_menu = undefined,
         .toast_overlay = undefined,
-        .winproto = null,
+        .winproto = .none,
     };
 
     // Create the window
@@ -207,11 +207,6 @@ pub fn init(self: *Window, app: *App) !void {
     _ = c.g_signal_connect_data(gtk_window, "notify::maximized", c.G_CALLBACK(&gtkWindowNotifyMaximized), self, null, c.G_CONNECT_DEFAULT);
     _ = c.g_signal_connect_data(gtk_window, "notify::fullscreened", c.G_CALLBACK(&gtkWindowNotifyFullscreened), 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)) {
@@ -379,7 +374,11 @@ pub fn updateConfig(
     self: *Window,
     config: *const configpkg.Config,
 ) !void {
-    if (self.winproto) |*v| try v.updateConfigEvent(config);
+    self.winproto.updateConfigEvent(config) catch |err| {
+        // We want to continue attempting to make the other config
+        // changes necessary so we just log the error and continue.
+        log.warn("failed to update window protocol config error={}", .{err});
+    };
 
     // We always resync our appearance whenever the config changes.
     try self.syncAppearance(config);
@@ -391,16 +390,52 @@ pub fn updateConfig(
 /// 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");
+    self.winproto.syncAppearance() catch |err| {
+        log.warn("failed to sync winproto appearance error={}", .{err});
+    };
+
+    toggleCssClass(
+        @ptrCast(self.window),
+        "background",
+        config.@"background-opacity" >= 1,
+    );
+
+    // If we are disabling CSDs then disable them right away.
+    const csd_enabled = self.winproto.clientSideDecorationEnabled();
+    c.gtk_window_set_decorated(self.window, @intFromBool(csd_enabled));
+
+    // If we are not decorated then we hide the titlebar.
+    self.headerbar.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.
+    if ((comptime adwaita.versionAtLeast(0, 0, 0)) and
+        adwaita.enabled(&self.app.config))
+    {
+        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),
+            );
+        }
     }
+}
 
-    // Window protocol specific appearance updates
-    if (self.winproto) |*v| v.syncAppearance() catch |err| {
-        log.warn("failed to sync window protocol appearance error={}", .{err});
-    };
+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
@@ -440,7 +475,7 @@ fn initActions(self: *Window) void {
 pub fn deinit(self: *Window) void {
     c.gtk_widget_unparent(@ptrCast(self.context_menu));
 
-    if (self.winproto) |*v| v.deinit(self.app.core_app.alloc);
+    self.winproto.deinit(self.app.core_app.alloc);
 
     if (self.adw_tab_overview_focus_timer) |timer| {
         _ = c.g_source_remove(timer);
@@ -548,15 +583,11 @@ 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.
-    self.headerbar.setVisible(new_decorated);
+    self.app.config.@"window-decoration" = switch (self.app.config.@"window-decoration") {
+        .client, .server => .none,
+        .none => .server,
+    };
+    self.updateConfig(&self.app.config) catch {};
 }
 
 /// Grabs focus on the currently selected tab.
@@ -623,17 +654,14 @@ 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);
 }
 
 fn gtkWindowNotifyFullscreened(

src/apprt/gtk/headerbar.zig

@@ -18,9 +18,6 @@ pub const HeaderBar = union(enum) {
         } else {
             HeaderBarGtk.init(self);
         }
-
-        if (!window.app.config.@"gtk-titlebar" or !window.app.config.@"window-decoration")
-            self.setVisible(false);
     }
 
     pub fn setVisible(self: HeaderBar, visible: bool) void {

src/apprt/gtk/winproto.zig

@@ -62,7 +62,7 @@ pub const App = union(Protocol) {
 
 /// Per-Window state for the underlying windowing protocol.
 ///
-/// In both X and Wayland, the terminology used is "Surface" and this is
+/// In Wayland, the terminology used is "Surface" and for it, this is
 /// really "Surface"-specific state. But Ghostty uses the term "Surface"
 /// heavily to mean something completely different, so we use "Window" here
 /// to better match what it generally maps to in the Ghostty codebase.
@@ -125,4 +125,10 @@ pub const Window = union(Protocol) {
             inline else => |*v| try v.syncAppearance(),
         }
     }
+
+    pub fn clientSideDecorationEnabled(self: Window) bool {
+        return switch (self) {
+            inline else => |v| v.clientSideDecorationEnabled(),
+        };
+    }
 };

src/apprt/gtk/winproto/noop.zig

@@ -53,4 +53,12 @@ pub const Window = struct {
     pub fn resizeEvent(_: *Window) !void {}
 
     pub fn syncAppearance(_: *Window) !void {}
+
+    /// This returns true if CSD is enabled for this window. This
+    /// should be the actual present state of the window, not the
+    /// desired state.
+    pub fn clientSideDecorationEnabled(self: Window) bool {
+        _ = self;
+        return true;
+    }
 };