[gdk] Add gdk_window_has_native() function

https://bugzilla.gnome.org/show_bug.cgi?id=622677

docs/reference/gdk/gdk3-sections.txt

@@ -595,6 +595,7 @@ gdk_window_move_resize
 gdk_window_scroll
 gdk_window_move_region
 gdk_window_flush
+gdk_window_has_native
 gdk_window_ensure_native
 gdk_window_reparent
 gdk_window_clear

gdk/gdk.symbols

@@ -661,6 +661,7 @@ gdk_window_get_root_coords
 gdk_window_get_deskrelative_origin
 gdk_window_set_support_multidevice
 gdk_window_get_support_multidevice
+gdk_window_has_native
 gdk_window_set_background
 gdk_window_set_back_pixmap
 gdk_window_set_cursor

gdk/gdkwindow.c

@@ -2399,6 +2399,29 @@ from_embedder (GdkWindowObject *window,
                  offscreen_x, offscreen_y);
 }
 
+/**
+ * gdk_window_has_native:
+ * @window: a #GdkWindow
+ *
+ * Checks whether the window has a native window or not. Note that
+ * you can use gdk_window_ensure_native() if a native window is needed.
+ *
+ * Returns: %TRUE if the %window has a native window, %FALSE otherwise.
+ *
+ * Since: 2.22
+ */
+gboolean
+gdk_window_has_native (GdkWindow *window)
+{
+  GdkWindowObject *w;
+
+  g_return_val_if_fail (GDK_IS_WINDOW (window), FALSE);
+
+  w = GDK_WINDOW_OBJECT (window);
+
+  return w->parent == NULL || w->parent->impl != w->impl;
+}
+
 /**
  * gdk_window_get_position:
  * @window: a #GdkWindow

gdk/gdkwindow.h

@@ -716,6 +716,7 @@ GdkWindow*    gdk_window_lookup_for_display (GdkDisplay      *display,
 
 /* GdkWindow */
 
+gboolean      gdk_window_has_native         (GdkWindow       *window);
 void              gdk_window_set_type_hint (GdkWindow        *window,
                                             GdkWindowTypeHint hint);
 GdkWindowTypeHint gdk_window_get_type_hint (GdkWindow        *window);