[gtk+] gtkwindow: Add private API to mark as subsurface

[Carlos Garnacho <carlosg src gnome org>]

commit c38651cac468f92c8dfdbc3ed1c9eb3d67a93828
Author: Carlos Garnacho <carlosg gnome org>
Date:   Thu Aug 21 17:34:09 2014 +0200

    gtkwindow: Add private API to mark as subsurface
    
    This is a rather hackish way to let GTK+ widgets declare popup windows
    as subsurfaces, so they may work on wayland without the need of xdg_popup,
    and without many changes yet on the GTK+ side.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=695504

 gtk/gtkwindow.c        |   20 ++++++++++++++++++++
 gtk/gtkwindowprivate.h |    3 +++
 2 files changed, 23 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index f0b8aea..514c6db 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -229,6 +229,8 @@ struct _GtkWindowPrivate
 
   guint    drag_possible             : 1;
 
+  guint    use_subsurface            : 1;
+
   GtkGesture *multipress_gesture;
 };
 
@@ -6337,6 +6339,12 @@ gtk_window_realize (GtkWidget *widget)
       break;
     }
 
+#ifdef GDK_WINDOWING_WAYLAND
+  if (priv->use_subsurface &&
+      GDK_IS_WAYLAND_DISPLAY (gtk_widget_get_display (widget)))
+    attributes.window_type = GDK_WINDOW_SUBSURFACE;
+#endif
+
   attributes.title = priv->title;
   attributes.wmclass_name = priv->wmclass_name;
   attributes.wmclass_class = priv->wmclass_class;
@@ -11697,3 +11705,15 @@ gtk_window_enable_debugging (GtkWindow *window,
   else
     gtk_window_set_debugging (TRUE, TRUE, warn);
 }
+
+void
+gtk_window_set_use_subsurface (GtkWindow *window,
+                               gboolean   use_subsurface)
+{
+  GtkWindowPrivate *priv = window->priv;
+
+  g_return_if_fail (GTK_IS_WINDOW (window));
+  g_return_if_fail (!gtk_widget_get_realized (GTK_WIDGET (window)));
+
+  priv->use_subsurface = use_subsurface;
+}
diff --git a/gtk/gtkwindowprivate.h b/gtk/gtkwindowprivate.h
index 3d7b086..ce19d1b 100644
--- a/gtk/gtkwindowprivate.h
+++ b/gtk/gtkwindowprivate.h
@@ -119,6 +119,9 @@ void    _gtk_window_get_popover_position (GtkWindow                   *window,
 GdkPixbuf *gtk_window_get_icon_for_size (GtkWindow *window,
                                          gint       size);
 
+void       gtk_window_set_use_subsurface (GtkWindow *window,
+                                          gboolean   use_subsurface);
+
 G_END_DECLS
 
 #endif /* __GTK_WINDOW_PRIVATE_H__ */