wayland/gtk-shell: Add titlebar_gesture request

This allows client to delegate titlebar gestures to the compositor,
which allows for better consistency with server-side decorations,
and a wider range of actions (including lower-on-middle-click).

The protocol addition is based on a suggestion from Carlos Garnacho
and Jonas Ådahl.

https://gitlab.gnome.org/GNOME/mutter/-/issues/602

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1944>

src/wayland/meta-wayland-gtk-shell.c

@@ -208,6 +208,96 @@ gtk_surface_request_focus (struct wl_client   *client,
     }
 }
 
+static void
+gtk_surface_titlebar_gesture (struct wl_client   *client,
+                              struct wl_resource *resource,
+                              uint32_t            serial,
+                              struct wl_resource *seat_resource,
+                              uint32_t            gesture)
+{
+  MetaWaylandGtkSurface *gtk_surface = wl_resource_get_user_data (resource);
+  MetaWaylandSurface *surface = gtk_surface->surface;
+  MetaWaylandSeat *seat = wl_resource_get_user_data (seat_resource);
+  GDesktopTitlebarAction action = G_DESKTOP_TITLEBAR_ACTION_NONE;
+  MetaWindow *window;
+  float x, y;
+
+  if (!surface)
+    return;
+
+  window = meta_wayland_surface_get_window (surface);
+  if (!window)
+    return;
+
+  if (!meta_wayland_seat_get_grab_info (seat, surface, serial, FALSE, &x, &y))
+    return;
+
+  switch (gesture)
+    {
+    case GTK_SURFACE1_GESTURE_DOUBLE_CLICK:
+      action = meta_prefs_get_action_double_click_titlebar ();
+      break;
+    case GTK_SURFACE1_GESTURE_RIGHT_CLICK:
+      action = meta_prefs_get_action_right_click_titlebar ();
+      break;
+    case GTK_SURFACE1_GESTURE_MIDDLE_CLICK:
+      action = meta_prefs_get_action_middle_click_titlebar ();
+      break;
+    default:
+      wl_resource_post_error (resource,
+                              GTK_SURFACE1_ERROR_INVALID_GESTURE,
+                              "Invalid gesture passed");
+      break;
+    }
+
+  switch (action)
+    {
+    case G_DESKTOP_TITLEBAR_ACTION_TOGGLE_MAXIMIZE:
+      if (META_WINDOW_MAXIMIZED (window))
+        meta_window_unmaximize (window, META_MAXIMIZE_BOTH);
+      else
+        meta_window_maximize (window, META_MAXIMIZE_BOTH);
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_TOGGLE_MAXIMIZE_HORIZONTALLY:
+      if (META_WINDOW_MAXIMIZED_HORIZONTALLY (window))
+        meta_window_unmaximize (window, META_MAXIMIZE_HORIZONTAL);
+      else
+        meta_window_maximize (window, META_MAXIMIZE_HORIZONTAL);
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_TOGGLE_MAXIMIZE_VERTICALLY:
+      if (META_WINDOW_MAXIMIZED_VERTICALLY (window))
+        meta_window_unmaximize (window, META_MAXIMIZE_VERTICAL);
+      else
+        meta_window_maximize (window, META_MAXIMIZE_VERTICAL);
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_MINIMIZE:
+      meta_window_minimize (window);
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_LOWER:
+      {
+        uint32_t timestamp;
+
+        timestamp = meta_display_get_current_time_roundtrip (window->display);
+        meta_window_lower_with_transients (window, timestamp);
+      }
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_MENU:
+      meta_window_show_menu (window, META_WINDOW_MENU_WM, x, y);
+      break;
+
+    case G_DESKTOP_TITLEBAR_ACTION_TOGGLE_SHADE:
+      g_warning ("No shade! The library is closed.");
+      G_GNUC_FALLTHROUGH;
+    default:
+      return;
+    }
+}
+
 static void
 gtk_surface_release (struct wl_client   *client,
                      struct wl_resource *resource)
@@ -221,7 +311,8 @@ static const struct gtk_surface1_interface meta_wayland_gtk_surface_interface =
   gtk_surface_unset_modal,
   gtk_surface_present,
   gtk_surface_request_focus,
-  gtk_surface_release
+  gtk_surface_release,
+  gtk_surface_titlebar_gesture
 };
 
 static void

src/wayland/meta-wayland-versions.h

@@ -43,7 +43,7 @@
 #define META_WL_SEAT_VERSION                5
 #define META_WL_OUTPUT_VERSION              2
 #define META_XSERVER_VERSION                1
-#define META_GTK_SHELL1_VERSION             4
+#define META_GTK_SHELL1_VERSION             5
 #define META_WL_SUBCOMPOSITOR_VERSION       1
 #define META_ZWP_POINTER_GESTURES_V1_VERSION    1
 #define META_ZXDG_EXPORTER_V1_VERSION       1

src/wayland/protocol/gtk-shell.xml

@@ -1,6 +1,6 @@
 <protocol name="gtk">
 
-  <interface name="gtk_shell1" version="4">
+  <interface name="gtk_shell1" version="5">
     <description summary="gtk specific extensions">
       gtk_shell is a protocol extension providing additional features for
       clients implementing it.
@@ -35,7 +35,7 @@
     </request>
   </interface>
 
-  <interface name="gtk_surface1" version="4">
+  <interface name="gtk_surface1" version="5">
     <request name="set_dbus_properties">
       <arg name="application_id" type="string" allow-null="true"/>
       <arg name="app_menu_path" type="string" allow-null="true"/>
@@ -85,6 +85,23 @@
 
     <!-- Version 4 additions -->
     <request name="release" type="destructor" since="4"/>
+
+    <!-- Version 5 additions -->
+    <enum name="gesture" since="5">
+      <entry name="double_click" value="1"/>
+      <entry name="right_click" value="2"/>
+      <entry name="middle_click" value="3"/>
+    </enum>
+
+    <enum name="error" since="5">
+      <entry name="invalid_gesture" value="0"/>
+    </enum>
+
+    <request name="titlebar_gesture" since="5">
+      <arg name="serial" type="uint"/>
+      <arg name="seat" type="object" interface="wl_seat"/>
+      <arg name="gesture" type="uint" enum="gesture"/>
+    </request>
   </interface>
 
 </protocol>