[gtk/wip/chergert/macos-iosurface: 1/3] gdk/gl: add default_framebuffer to GdkGLContext

[Christian Hergert <chergert src gnome org>]

commit 113cc6d363cea4bc1ef135cb7c2e18427f322a3b
Author: Christian Hergert <christian hergert me>
Date:   Thu Feb 10 21:50:02 2022 -0800

    gdk/gl: add default_framebuffer to GdkGLContext
    
    Some GdkGLContext implementations may need to use a default framebuffer
    other than 0. This provides a convenient place for that which can be
    accessed by the GskGLRenderer without further plumbing abstractions.

 gdk/gdkglcontextprivate.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gdk/gdkglcontextprivate.h b/gdk/gdkglcontextprivate.h
index ff11349b3e..974ba67e84 100644
--- a/gdk/gdkglcontextprivate.h
+++ b/gdk/gdkglcontextprivate.h
@@ -53,6 +53,8 @@ struct _GdkGLContext
 
   /* We store the old drawn areas to support buffer-age optimizations */
   cairo_region_t *old_updated_area[2];
+
+  guint default_framebuffer;
 };
 
 struct _GdkGLContextClass