[mutter] ui: Disable gdk's gl support

[Adel Gadllah <agadllah src gnome org>]

commit fea7ac84ee493ba17cd5a1a51dbd8cfc8692e4c3
Author: Adel Gadllah <adel gadllah gmail com>
Date:   Thu Jan 8 11:14:38 2015 +0100

    ui: Disable gdk's gl support
    
    This fixes a deadlock on wayland.

 src/ui/ui.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/src/ui/ui.c b/src/ui/ui.c
index 1e2d350..b82fba1 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -48,11 +48,20 @@ struct _MetaUI
 void
 meta_ui_init (void)
 {
+  const char *gdk_gl_env = NULL;
   gdk_set_allowed_backends ("x11");
 
+  gdk_gl_env = g_getenv ("GDK_GL");
+  g_setenv("GDK_GL", "disable", TRUE);
+
   if (!gtk_init_check (NULL, NULL))
     meta_fatal ("Unable to open X display %s\n", XDisplayName (NULL));
 
+  if (gdk_gl_env)
+    g_setenv("GDK_GL", gdk_gl_env, TRUE);
+  else
+    unsetenv("GDK_GL");
+
   /* We need to be able to fully trust that the window and monitor sizes
      that Gdk reports corresponds to the X ones, so we disable the automatic
      scale handling */