3 files changed, 52 insertions, 2 deletions

diff --git a/clutter/gdk/clutter-backend-gdk.c b/clutter/gdk/clutter-backend-gdk.c
index a464e684b..fab7bf0c5 100644
--- a/clutter/gdk/clutter-backend-gdk.c
+++ b/clutter/gdk/clutter-backend-gdk.c
@@ -23,6 +23,8 @@
 #include "config.h"
 #endif
 
+#define CLUTTER_ENABLE_EXPERIMENTAL_API
+
 #include <glib/gi18n-lib.h>
 
 #include <string.h>
@@ -83,6 +85,29 @@ static GdkDisplay  *_foreign_dpy = NULL;
 
 static gboolean disable_event_retrieval = FALSE;
 
+void
+_clutter_backend_gdk_reset_framebuffer (ClutterBackendGdk *backend_gdk)
+{
+  if (backend_gdk->dummy_onscreen == COGL_INVALID_HANDLE)
+    {
+      CoglContext *context =
+        clutter_backend_get_cogl_context (CLUTTER_BACKEND (backend_gdk));
+      CoglError *internal_error = NULL;
+
+      backend_gdk->dummy_onscreen = cogl_onscreen_new (context, 1, 1);
+
+      if (!cogl_framebuffer_allocate (COGL_FRAMEBUFFER (backend_gdk->dummy_onscreen),
+                                      &internal_error))
+        {
+          g_error ("Unable to create dummy onscreen: %s", internal_error->message);
+          cogl_error_free (internal_error);
+          return;
+        }
+    }
+
+  cogl_set_framebuffer (COGL_FRAMEBUFFER (backend_gdk->dummy_onscreen));
+}
+
 static void
 clutter_backend_gdk_init_settings (ClutterBackendGdk *backend_gdk)
 {
@@ -226,6 +251,8 @@ clutter_backend_gdk_finalize (GObject *gobject)
 {
   ClutterBackendGdk *backend_gdk = CLUTTER_BACKEND_GDK (gobject);
 
+  g_clear_pointer (&backend_gdk->dummy_onscreen, cogl_object_unref);
+
   gdk_window_remove_filter (NULL, cogl_gdk_filter, backend_gdk);
   g_object_unref (backend_gdk->display);
 
@@ -413,7 +440,7 @@ clutter_backend_gdk_class_init (ClutterBackendGdkClass *klass)
 static void
 clutter_backend_gdk_init (ClutterBackendGdk *backend_gdk)
 {
-  /* nothing to do here */
+  backend_gdk->dummy_onscreen = COGL_INVALID_HANDLE;
 }
 
 /**
diff --git a/clutter/gdk/clutter-backend-gdk.h b/clutter/gdk/clutter-backend-gdk.h
index fb5411315..7f234590c 100644
--- a/clutter/gdk/clutter-backend-gdk.h
+++ b/clutter/gdk/clutter-backend-gdk.h
@@ -50,6 +50,8 @@ struct _ClutterBackendGdk
   GdkDisplay *display;
   GdkScreen  *screen;
 
+  CoglOnscreen *dummy_onscreen;
+
   ClutterDeviceManager *device_manager;
 };
 
@@ -67,6 +69,8 @@ void   _clutter_backend_gdk_events_init (ClutterBackend *backend);
 void   _clutter_backend_gdk_update_setting (ClutterBackendGdk *backend,
                                             const gchar *name);
 
+void   _clutter_backend_gdk_reset_framebuffer (ClutterBackendGdk *backend);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_BACKEND_GDK_H__ */
diff --git a/clutter/gdk/clutter-stage-gdk.c b/clutter/gdk/clutter-stage-gdk.c
index 5cf394797..7152b11fb 100644
--- a/clutter/gdk/clutter-stage-gdk.c
+++ b/clutter/gdk/clutter-stage-gdk.c
@@ -182,7 +182,26 @@ clutter_stage_gdk_unrealize (ClutterStageWindow *stage_window)
 			 "clutter-stage-window", NULL);
 
       if (stage_gdk->foreign_window)
-	g_object_unref (stage_gdk->window);
+        {
+          ClutterStageCogl *stage_cogl = CLUTTER_STAGE_COGL (stage_window);
+          ClutterBackendGdk *backend_gdk = CLUTTER_BACKEND_GDK (stage_cogl->backend);
+
+          g_object_unref (stage_gdk->window);
+
+          /* Clutter still uses part of the deprecated stateful API of
+           * Cogl (in particulart cogl_set_framebuffer). It means Cogl
+           * can keep an internal reference to the onscreen object we
+           * rendered to. In the case of foreign window, we want to
+           * avoid this, as we don't know what's going to happen to
+           * that window.
+           *
+           * The following call sets the current Cogl framebuffer to a
+           * dummy 1x1 one if we're unrealizing the current one, so
+           * Cogl doesn't keep any reference to the foreign window.
+           */
+          if (cogl_get_draw_framebuffer () == COGL_FRAMEBUFFER (stage_cogl->onscreen))
+            _clutter_backend_gdk_reset_framebuffer (backend_gdk);
+        }
       else
 	gdk_window_destroy (stage_gdk->window);