[gtk+] gdk: Allow display subclasses to override the type used for windows

[Matthias Clasen <matthiasc src gnome org>]

commit af7afbbe06690281d9703aaab7d1b9522cede3cb
Author: Benjamin Otte <otte redhat com>
Date:   Tue Dec 21 03:13:55 2010 +0100

    gdk: Allow display subclasses to override the type used for windows
    
    We want to have different window types for different displays, so we can
    write code like this:
    
      #if GDK_WINDOWING_X11
        if (GDK_IS_X11_WINDOW (window))
          {
            /* do x11 stuff */
          }
        else
      #endif
      #if GDK_WINDOWING_WAYLAND
        if (GDK_IS_WAYLAND_WINDOW (window))
          {
            /* do wayland stuff */
          }
        else
      #endif
          {
            /* do stuff for unsupported system */
        }
    
    This requires different GdkWindow types and we currently don't have
    that, as only the GdkWindowImpl differs. With this method, every backend
    defines a custom type that's just a simple subclass of GdkWindow. This
    way GdkWindow behaves like all the other types (visuals, screens,
    displays) and we can write code like the above.

 gdk/gdkdisplay.c        |    3 ++-
 gdk/gdkdisplayprivate.h |    2 ++
 2 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkdisplay.c b/gdk/gdkdisplay.c
index ba912f2..117f906 100644
--- a/gdk/gdkdisplay.c
+++ b/gdk/gdkdisplay.c
@@ -186,6 +186,7 @@ gdk_display_class_init (GdkDisplayClass *class)
   object_class->dispose = gdk_display_dispose;
 
   class->get_app_launch_context = gdk_display_real_get_app_launch_context;
+  class->window_type = GDK_TYPE_WINDOW;
 
   /**
    * GdkDisplay::opened:
@@ -2501,7 +2502,7 @@ _gdk_display_create_window_impl (GdkDisplay       *display,
 GdkWindow *
 _gdk_display_create_window (GdkDisplay *display)
 {
-  return g_object_new (GDK_TYPE_WINDOW, NULL);
+  return g_object_new (GDK_DISPLAY_GET_CLASS (display)->window_type, NULL);
 }
 
 /**
diff --git a/gdk/gdkdisplayprivate.h b/gdk/gdkdisplayprivate.h
index 608e7b1..29ab846 100644
--- a/gdk/gdkdisplayprivate.h
+++ b/gdk/gdkdisplayprivate.h
@@ -115,6 +115,8 @@ struct _GdkDisplayClass
 {
   GObjectClass parent_class;
 
+  GType window_type;          /* type for native windows for this display, set in class_init */
+
   G_CONST_RETURN gchar *     (*get_name)           (GdkDisplay *display);
   gint                       (*get_n_screens)      (GdkDisplay *display);
   GdkScreen *                (*get_screen)         (GdkDisplay *display,