window: Improve detection of edge constraint support

Instead of relying on special values of edge constraints, this
patch adds an internal-only gdk_window_supports_edge_constraints()
function that by default returns FALSE, and is implemented by
GdkWindowWayland and GdkWindowX11.

This way, we can properly detect server-side support for this
feature and adapt accordingly.

https://bugzilla.gnome.org/show_bug.cgi?id=783669

gdk/gdk-private.h

@@ -21,6 +21,8 @@ void            gdk_gl_set_flags                (GdkGLFlags flags);
 void            gdk_window_freeze_toplevel_updates      (GdkWindow *window);
 void            gdk_window_thaw_toplevel_updates        (GdkWindow *window);
 
+gboolean        gdk_window_supports_edge_constraints    (GdkWindow *window);
+
 GdkRenderingMode gdk_display_get_rendering_mode (GdkDisplay       *display);
 void             gdk_display_set_rendering_mode (GdkDisplay       *display,
                                                  GdkRenderingMode  mode);

gdk/gdkwindow.c

@@ -8234,3 +8234,19 @@ gdk_window_show_window_menu (GdkWindow *window,
   else
     return FALSE;
 }
+
+gboolean
+gdk_window_supports_edge_constraints (GdkWindow *window)
+{
+  GdkWindowImplClass *impl_class;
+
+  g_return_val_if_fail (GDK_IS_WINDOW (window), FALSE);
+  g_return_val_if_fail (!GDK_WINDOW_DESTROYED (window), FALSE);
+
+  impl_class = GDK_WINDOW_IMPL_GET_CLASS (window->impl);
+
+  if (impl_class->supports_edge_constraints)
+    return impl_class->supports_edge_constraints (window);
+  else
+    return FALSE;
+}

gdk/gdkwindowimpl.h

@@ -269,6 +269,7 @@ struct _GdkWindowImplClass
 					   gboolean        attached,
                                            GdkGLContext   *share,
                                            GError        **error);
+  gboolean     (* supports_edge_constraints)(GdkWindow    *window);
 };
 
 /* Interface Functions */

gdk/wayland/gdkwindow-wayland.c

@@ -3637,6 +3637,14 @@ gdk_wayland_window_show_window_menu (GdkWindow *window,
   return TRUE;
 }
 
+static gboolean
+gdk_wayland_window_supports_edge_constraints (GdkWindow *window)
+{
+  GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
+
+  return gtk_surface1_get_version (impl->display_server.gtk_surface) > GTK_SURFACE1_CONFIGURE_EDGES_SINCE_VERSION;
+}
+
 static void
 _gdk_window_impl_wayland_class_init (GdkWindowImplWaylandClass *klass)
 {
@@ -3716,6 +3724,7 @@ _gdk_window_impl_wayland_class_init (GdkWindowImplWaylandClass *klass)
   impl_class->set_shadow_width = gdk_wayland_window_set_shadow_width;
   impl_class->show_window_menu = gdk_wayland_window_show_window_menu;
   impl_class->create_gl_context = gdk_wayland_window_create_gl_context;
+  impl_class->supports_edge_constraints = gdk_wayland_window_supports_edge_constraints;
 
   signals[COMMITTED] = g_signal_new ("committed",
                                      G_TYPE_FROM_CLASS (object_class),

gdk/x11/gdkdisplay-x11.c

@@ -199,7 +199,6 @@ do_edge_constraint_state_check (GdkWindow      *window,
 {
   GdkToplevelX11 *toplevel = _gdk_x11_window_get_toplevel (window);
   GdkWindowState local_set, local_unset;
-  GdkScreen *screen = GDK_WINDOW_SCREEN (window);
   guint edge_constraints;
 
   local_set = *set;
@@ -210,8 +209,7 @@ do_edge_constraint_state_check (GdkWindow      *window,
    * implementation. If it supports _GTK_EDGE_CONSTRAINTS, however, remove
    * the GDK_WINDOW_STATE_TILED flag explicitly.
    */
-  if (!gdk_x11_screen_supports_net_wm_hint (screen,
+  if (!gdk_window_supports_edge_constraints (window))
-                                            gdk_atom_intern_static_string ("_GTK_EDGE_CONSTRAINTS")))
     {
       /* FIXME: we rely on implementation details of mutter here:
        * mutter only tiles horizontally, and sets maxvert when it does

gdk/x11/gdkwindow-x11.c

@@ -210,6 +210,13 @@ gdk_x11_window_get_unscaled_size (GdkWindow *window,
     *unscaled_height = impl->unscaled_height;
 }
 
+static gboolean
+gdk_x11_window_supports_edge_constraints (GdkWindow *window)
+{
+  return gdk_x11_screen_supports_net_wm_hint (GDK_WINDOW_SCREEN (window),
+                                              gdk_atom_intern_static_string ("_GTK_EDGE_CONSTRAINTS"));
+}
+
 static void
 set_sync_counter(Display     *display,
 		 XSyncCounter counter,
@@ -5071,4 +5078,5 @@ gdk_window_impl_x11_class_init (GdkWindowImplX11Class *klass)
   impl_class->show_window_menu = gdk_x11_window_show_window_menu;
   impl_class->create_gl_context = gdk_x11_window_create_gl_context;
   impl_class->get_unscaled_size = gdk_x11_window_get_unscaled_size;
+  impl_class->supports_edge_constraints = gdk_x11_window_supports_edge_constraints;
 }

gtk/gtkwindow.c

@@ -1699,6 +1699,7 @@ edge_under_coordinates (GtkWindow     *window,
   GtkStyleContext *context;
   gint handle_v, handle_h;
   GtkBorder border;
+  gboolean supports_edge_constraints;
 
   if (priv->type != GTK_WINDOW_TOPLEVEL ||
       !priv->client_decorated ||
@@ -1707,7 +1708,16 @@ edge_under_coordinates (GtkWindow     *window,
       priv->maximized)
     return FALSE;
 
-  if (priv->tiled && !priv->edge_constraints)
+  supports_edge_constraints = gdk_window_supports_edge_constraints (_gtk_widget_get_window (GTK_WIDGET (window)));
+
+  if (!supports_edge_constraints && priv->tiled)
+    return FALSE;
+
+  if (supports_edge_constraints &&
+      !(priv->edge_constraints & GDK_WINDOW_STATE_TOP_RESIZABLE) &&
+      !(priv->edge_constraints & GDK_WINDOW_STATE_RIGHT_RESIZABLE) &&
+      !(priv->edge_constraints & GDK_WINDOW_STATE_BOTTOM_RESIZABLE) &&
+      !(priv->edge_constraints & GDK_WINDOW_STATE_LEFT_RESIZABLE))
     return FALSE;
 
   _gtk_widget_get_allocation (GTK_WIDGET (window), &allocation);
@@ -1744,7 +1754,8 @@ edge_under_coordinates (GtkWindow     *window,
           edge != GDK_WINDOW_EDGE_SOUTH_WEST)
         return FALSE;
 
-      if (!(priv->edge_constraints & GDK_WINDOW_STATE_LEFT_RESIZABLE))
+      if (supports_edge_constraints &&
+          !(priv->edge_constraints & GDK_WINDOW_STATE_LEFT_RESIZABLE))
         return FALSE;
     }
   else if (x >= allocation.x + allocation.width - border.right - handle_h)
@@ -1754,7 +1765,8 @@ edge_under_coordinates (GtkWindow     *window,
           edge != GDK_WINDOW_EDGE_SOUTH_EAST)
         return FALSE;
 
-      if (!(priv->edge_constraints & GDK_WINDOW_STATE_RIGHT_RESIZABLE))
+      if (supports_edge_constraints &&
+          !(priv->edge_constraints & GDK_WINDOW_STATE_RIGHT_RESIZABLE))
         return FALSE;
     }
   else if (edge != GDK_WINDOW_EDGE_NORTH &&
@@ -1769,7 +1781,8 @@ edge_under_coordinates (GtkWindow     *window,
           edge != GDK_WINDOW_EDGE_NORTH_EAST)
         return FALSE;
 
-      if (!(priv->edge_constraints & GDK_WINDOW_STATE_TOP_RESIZABLE))
+      if (supports_edge_constraints &&
+          !(priv->edge_constraints & GDK_WINDOW_STATE_TOP_RESIZABLE))
         return FALSE;
     }
   else if (y > allocation.y + allocation.height - border.bottom - handle_v)
@@ -1779,7 +1792,8 @@ edge_under_coordinates (GtkWindow     *window,
           edge != GDK_WINDOW_EDGE_SOUTH_EAST)
         return FALSE;
 
-      if (!(priv->edge_constraints & GDK_WINDOW_STATE_BOTTOM_RESIZABLE))
+      if (supports_edge_constraints &&
+          !(priv->edge_constraints & GDK_WINDOW_STATE_BOTTOM_RESIZABLE))
         return FALSE;
     }
   else if (edge != GDK_WINDOW_EDGE_WEST &&