feat(apprt-gtk): port the GTK4/libadwaita app runtime

Ports ZIG/src/apprt/gtk into ghostty-apprt-gtk: every GObject class
(application, window, tab, split tree, surface + scrolled window,
child-exited banner, search/key-state/resize overlays, command palette,
global shortcuts, all dialogs, config wrapper) as glib subclasses with
the same GType names, properties, signals and template children; GDK
key translation; X11 and Wayland window-protocol helpers (blur, CSD,
quick terminal via gtk4-layer-shell); single-instance D-Bus IPC;
gsettings; cgroup scope creation.

build.rs compiles Ghostty's blueprints with blueprint-compiler and
bundles UI, CSS and icons into a gresource, as Ghostty's build does.

The core is not ported yet, so the crate defines the boundary it needs
in src/core.rs (CoreApp, CoreSurface, RtApp, RtSurface, Waker); the
spec is in docs/rewrite/notes/ghostty-apprt-gtk.md. ghostty-core will
implement these traits (the crate no longer depends on core to avoid a
cycle). examples/demo.rs runs the app with a dummy core that clears the
GLArea; it launches on Wayland without GTK criticals.

Stubs/open items: toggle_visibility, float_window, secure_input and
close_all_windows return false; inspector is a no-op; X11/Wayland
protocol code is untested against real compositors; gtk4-rs doesn't
expose the GLArea framebuffer id, so the renderer must query it.

Also registers ghostty-apprt and ghostty-cli in workspace.dependencies.

Test Plan:
- cargo test -p ghostty-apprt-gtk (36 tests)
- DEMO_QUIT_AFTER_MS=3000 cargo run -p ghostty-apprt-gtk --example demo

crates/ghostty-apprt-gtk/resources/ui/1.5/command-palette.blp

@@ -0,0 +1,110 @@
+using Gtk 4.0;
+using Gio 2.0;
+using Adw 1;
+
+Adw.Dialog dialog {
+  content-width: 700;
+  closed => $closed();
+
+  Adw.ToolbarView {
+    top-bar-style: flat;
+
+    [top]
+    Adw.HeaderBar {
+      [title]
+      Gtk.SearchEntry search {
+        hexpand: true;
+        placeholder-text: _("Execute a command…");
+        stop-search => $search_stopped();
+        activate => $search_activated();
+
+        styles [
+          "command-palette-search",
+        ]
+      }
+    }
+
+    Gtk.ScrolledWindow {
+      min-content-height: 300;
+
+      Gtk.ListView view {
+        show-separators: true;
+        single-click-activate: true;
+        activate => $row_activated();
+
+        model: Gtk.SingleSelection model {
+          model: Gtk.FilterListModel {
+            incremental: true;
+
+            filter: Gtk.AnyFilter {
+              Gtk.StringFilter {
+                expression: expr item as <$GhosttyCommand>.title;
+                search: bind search.text;
+              }
+
+              Gtk.StringFilter {
+                expression: expr item as <$GhosttyCommand>.action-key;
+                search: bind search.text;
+              }
+            };
+
+            model: Gio.ListStore source {
+              item-type: typeof<$GhosttyCommand>;
+            };
+          };
+        };
+
+        styles [
+          "rich-list",
+        ]
+
+        factory: Gtk.BuilderListItemFactory {
+          template Gtk.ListItem {
+            child: Gtk.Box {
+              orientation: horizontal;
+              spacing: 10;
+              tooltip-text: bind template.item as <$GhosttyCommand>.description;
+
+              Gtk.Box {
+                orientation: vertical;
+                hexpand: true;
+
+                Gtk.Label {
+                  ellipsize: end;
+                  halign: start;
+                  wrap: false;
+                  single-line-mode: true;
+
+                  styles [
+                    "title",
+                  ]
+
+                  label: bind template.item as <$GhosttyCommand>.title;
+                }
+
+                Gtk.Label {
+                  ellipsize: end;
+                  halign: start;
+                  wrap: false;
+                  single-line-mode: true;
+
+                  styles [
+                    "subtitle",
+                    "monospace",
+                  ]
+
+                  label: bind template.item as <$GhosttyCommand>.action-key;
+                }
+              }
+
+              Gtk.ShortcutLabel {
+                accelerator: bind template.item as <$GhosttyCommand>.action;
+                valign: center;
+              }
+            };
+          }
+        };
+      }
+    }
+  }
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/split-tree-split.blp

@@ -0,0 +1,20 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GhosttySplitTreeSplit: Adw.Bin {
+  styles [
+    "split",
+  ]
+
+  // The double-nesting is required due to a GTK bug where you can't
+  // bind the first child of a builder layout. If you do, you get a double
+  // dispose. Easiest way to see that is simply remove this and see the
+  // GTK critical errors (and sometimes crashes).
+  Adw.Bin {
+    Paned paned {
+      notify::max-position => $notify_max_position();
+      notify::min-position => $notify_min_position();
+      notify::position => $notify_position();
+    }
+  }
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/split-tree.blp

@@ -0,0 +1,25 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GhosttySplitTree: Box {
+  notify::tree => $notify_tree();
+  orientation: vertical;
+
+  Adw.Bin tree_bin {
+    visible: bind template.has-surfaces;
+    hexpand: true;
+    vexpand: true;
+  }
+
+  // This could be a lot more visually pleasing but in practice this doesn't
+  // ever happen at the time of writing this comment. A surface-less split
+  // tree always closes its parent.
+  Label {
+    visible: bind template.has-surfaces inverted;
+    // Purposely not localized currently because this shouldn't really
+    // ever appear. When we have a situation it does appear, we may want
+    // to change the styling and text so I don't want to burden localizers
+    // to handle this yet.
+    label: "No surfaces.";
+  }
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/surface-scrolled-window.blp

@@ -0,0 +1,11 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GhostttySurfaceScrolledWindow: Adw.Bin {
+  notify::surface => $notify_surface();
+
+  Gtk.ScrolledWindow {
+    hscrollbar-policy: never;
+    vscrollbar-policy: bind $scrollbar_policy(template.config) as <Gtk.PolicyType>;
+  }
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/tab.blp

@@ -0,0 +1,18 @@
+using Gtk 4.0;
+
+template $GhosttyTab: Box {
+  styles [
+    "tab",
+  ]
+
+  orientation: vertical;
+  hexpand: true;
+  vexpand: true;
+  title: bind $computed_title(template.config, split_tree.active-surface as <$GhosttySurface>.title, split_tree.active-surface as <$GhosttySurface>.title-override, template.title-override, split_tree.is-zoomed, split_tree.active-surface as <$GhosttySurface>.bell-ringing) as <string>;
+  tooltip: bind split_tree.active-surface as <$GhosttySurface>.pwd;
+
+  $GhosttySplitTree split_tree {
+    notify::active-surface => $notify_active_surface();
+    notify::tree => $notify_tree();
+  }
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/title-dialog.blp

@@ -0,0 +1,18 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GhosttyTitleDialog: Adw.AlertDialog {
+  body: _("Leave blank to restore the default title.");
+
+  responses [
+    cancel: _("Cancel"),
+    ok: _("OK") suggested,
+  ]
+
+  default-response: "ok";
+  focus-widget: entry;
+
+  extra-child: Entry entry {
+    activates-default: true;
+  };
+}

crates/ghostty-apprt-gtk/resources/ui/1.5/window.blp

@@ -0,0 +1,323 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GhosttyWindow: Adw.ApplicationWindow {
+  styles [
+    "window",
+  ]
+
+  close-request => $close_request();
+  realize => $realize();
+  notify::config => $notify_config();
+  notify::fullscreened => $notify_fullscreened();
+  notify::is-active => $notify_is_active();
+  notify::maximized => $notify_maximized();
+  notify::quick-terminal => $notify_quick_terminal();
+  notify::scale-factor => $notify_scale_factor();
+  default-width: 800;
+  default-height: 600;
+  // GTK4 grabs F10 input by default to focus the menubar icon. We want
+  // to disable this so that terminal programs can capture F10 (such as htop)
+  handle-menubar-accel: false;
+
+  content: Adw.TabOverview tab_overview {
+    create-tab => $overview_create_tab();
+    notify::open => $overview_notify_open();
+    view: tab_view;
+    enable-new-tab: true;
+    // Disable the title buttons (close, maximize, minimize, ...)
+    // *inside* the tab overview if CSDs are disabled.
+    // We do spare the search button, though.
+    show-start-title-buttons: bind template.decorated;
+    show-end-title-buttons: bind template.decorated;
+
+    Adw.ToolbarView toolbar {
+      top-bar-style: bind template.toolbar-style;
+      bottom-bar-style: bind template.toolbar-style;
+
+      [top]
+      Adw.HeaderBar {
+        visible: bind template.headerbar-visible;
+
+        title-widget: Adw.WindowTitle {
+          title: bind template.title;
+          // Blueprint auto-formatter won't let me split this into multiple
+          // lines. Let me explain myself. All parameters to a closure are used
+          // as notifications to recompute the value of the closure. All
+          // elements of a property chain are also subscribed to for changes.
+          // This one long, ugly line saves us from manually building up this
+          // massive notify chain in code.
+          subtitle: bind $computed_subtitle(template.config, tab_view.selected-page.child as <$GhosttyTab>.active-surface as <$GhosttySurface>.pwd) as <string>;
+        };
+
+        [start]
+        Adw.SplitButton {
+          clicked => $new_tab();
+          icon-name: "tab-new-symbolic";
+          tooltip-text: _("New Tab");
+          dropdown-tooltip: _("New Split");
+          menu-model: split_menu;
+          can-focus: false;
+          focus-on-click: false;
+        }
+
+        [end]
+        Gtk.Box {
+          Gtk.ToggleButton {
+            icon-name: "view-grid-symbolic";
+            tooltip-text: _("View Open Tabs");
+            active: bind tab_overview.open bidirectional;
+            can-focus: false;
+            focus-on-click: false;
+          }
+
+          Gtk.MenuButton {
+            notify::active => $notify_menu_active();
+            icon-name: "open-menu-symbolic";
+            menu-model: main_menu;
+            tooltip-text: _("Main Menu");
+            can-focus: false;
+          }
+        }
+      }
+
+      [top]
+      Adw.TabBar tab_bar {
+        autohide: bind template.tabs-autohide;
+        expand-tabs: bind template.tabs-wide;
+        view: tab_view;
+        visible: bind template.tabs-visible;
+
+        [start]
+        Gtk.Box {
+          orientation: horizontal;
+          visible: bind $titlebar_style_is_tabs(template.titlebar-style) as <bool>;
+
+          Gtk.WindowControls {
+            side: start;
+          }
+
+          Adw.SplitButton {
+            styles [
+              "flat",
+            ]
+
+            clicked => $new_tab();
+            icon-name: "tab-new-symbolic";
+            tooltip-text: _("New Tab");
+            dropdown-tooltip: _("New Split");
+            menu-model: split_menu;
+            can-focus: false;
+            focus-on-click: false;
+          }
+        }
+
+        [end]
+        Gtk.Box {
+          orientation: horizontal;
+          visible: bind $titlebar_style_is_tabs(template.titlebar-style) as <bool>;
+
+          Gtk.ToggleButton {
+            styles [
+              "flat",
+            ]
+
+            icon-name: "view-grid-symbolic";
+            tooltip-text: _("View Open Tabs");
+            active: bind tab_overview.open bidirectional;
+            can-focus: false;
+            focus-on-click: false;
+          }
+
+          Gtk.MenuButton {
+            styles [
+              "flat",
+            ]
+
+            notify::active => $notify_menu_active();
+            icon-name: "open-menu-symbolic";
+            menu-model: main_menu;
+            tooltip-text: _("Main Menu");
+            can-focus: false;
+          }
+
+          Gtk.WindowControls {
+            side: end;
+          }
+        }
+      }
+
+      Box {
+        orientation: vertical;
+
+        $GhosttyDebugWarning {
+          visible: bind template.debug;
+        }
+
+        Adw.ToastOverlay toast_overlay {
+          Adw.TabView tab_view {
+            notify::n-pages => $notify_n_pages();
+            notify::selected-page => $notify_selected_page();
+            close-page => $close_page();
+            page-attached => $page_attached();
+            page-detached => $page_detached();
+            create-window => $tab_create_window();
+            setup-menu => $setup_tab_menu();
+            menu-model: tab_context_menu;
+            shortcuts: none;
+          }
+        }
+      }
+    }
+  };
+}
+
+menu split_menu {
+  item {
+    label: _("Split Up");
+    action: "win.split-up";
+  }
+
+  item {
+    label: _("Split Down");
+    action: "win.split-down";
+  }
+
+  item {
+    label: _("Split Left");
+    action: "win.split-left";
+  }
+
+  item {
+    label: _("Split Right");
+    action: "win.split-right";
+  }
+}
+
+menu main_menu {
+  section {
+    item {
+      label: _("Copy");
+      action: "win.copy";
+    }
+
+    item {
+      label: _("Paste");
+      action: "win.paste";
+    }
+  }
+
+  section {
+    item {
+      label: _("New Window");
+      action: "win.new-window";
+    }
+
+    item {
+      label: _("Close Window");
+      action: "win.close";
+    }
+  }
+
+  section {
+    item {
+      label: _("Change Tab Title…");
+      action: "win.prompt-tab-title";
+    }
+
+    item {
+      label: _("New Tab");
+      action: "win.new-tab";
+    }
+
+    item {
+      label: _("Close Tab");
+      action: "win.close-tab";
+      target: "this";
+    }
+  }
+
+  section {
+    submenu {
+      label: _("Split");
+
+      item {
+        label: _("Change Title…");
+        action: "win.prompt-surface-title";
+      }
+
+      item {
+        label: _("Split Up");
+        action: "win.split-up";
+      }
+
+      item {
+        label: _("Split Down");
+        action: "win.split-down";
+      }
+
+      item {
+        label: _("Split Left");
+        action: "win.split-left";
+      }
+
+      item {
+        label: _("Split Right");
+        action: "win.split-right";
+      }
+    }
+  }
+
+  section {
+    item {
+      label: _("Clear");
+      action: "win.clear";
+    }
+
+    item {
+      label: _("Reset");
+      action: "win.reset";
+    }
+  }
+
+  section {
+    item {
+      label: _("Command Palette");
+      action: "win.toggle-command-palette";
+    }
+
+    item {
+      label: _("Terminal Inspector");
+      action: "win.toggle-inspector";
+    }
+
+    item {
+      label: _("Open Configuration");
+      action: "app.open-config";
+    }
+
+    item {
+      label: _("Reload Configuration");
+      action: "app.reload-config";
+    }
+  }
+
+  section {
+    item {
+      label: _("About Ghostty");
+      action: "win.about";
+    }
+
+    item {
+      label: _("Quit");
+      action: "app.quit";
+    }
+  }
+}
+
+menu tab_context_menu {
+  item {
+    label: _("Change Tab Title…");
+    action: "win.prompt-context-tab-title";
+  }
+}