[gtk/wip/chergert/glproto] macos: only flush when not attached

[Christian Hergert <chergert src gnome org>]

commit f4d1d8e5e2a08fed8f27775fb4f5145ea15b3151
Author: Christian Hergert <chergert redhat com>
Date:   Mon Feb 8 09:53:46 2021 -0800

    macos: only flush when not attached
    
    This makes it so we only flush the context for the NSView, not the context
    that is the center of our center of the GL context spokes.

 gdk/macos/gdkmacosglcontext.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gdk/macos/gdkmacosglcontext.c b/gdk/macos/gdkmacosglcontext.c
index 8dd6bc2e00..28b3ed7ac7 100644
--- a/gdk/macos/gdkmacosglcontext.c
+++ b/gdk/macos/gdkmacosglcontext.c
@@ -362,7 +362,8 @@ gdk_macos_gl_context_end_frame (GdkDrawContext *context,
 
   GDK_DRAW_CONTEXT_CLASS (gdk_macos_gl_context_parent_class)->end_frame (context, painted);
 
-  [self->gl_context flushBuffer];
+  if (!self->is_attached)
+    [self->gl_context flushBuffer];
 }
 
 static void