[gtk/popup-shadow-width] macos: only flush when not attached

[Matthias Clasen <matthiasc src gnome org>]

commit 08dec07208be3d4324fa5178a15e06378bb808a7
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