[gtk/wip/otte/for-master: 2/2] gl: Use GL_BACK_LEFT

[Benjamin Otte <otte src gnome org>]

commit c4e2599a27732a7179c917c44ef133d8f8c82628
Author: Benjamin Otte <otte redhat com>
Date:   Wed Nov 3 19:49:08 2021 +0100

    gl: Use GL_BACK_LEFT
    
    The spec doesn't allow GL_BACK, but many drivers do. Use the
    spec-accepted equivalent instead.
    
    Fixed #4402

 gsk/gl/gskglrenderjob.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gsk/gl/gskglrenderjob.c b/gsk/gl/gskglrenderjob.c
index a904cf09d4..1862191118 100644
--- a/gsk/gl/gskglrenderjob.c
+++ b/gsk/gl/gskglrenderjob.c
@@ -4073,7 +4073,7 @@ get_framebuffer_format (guint framebuffer)
   glBindFramebuffer (GL_FRAMEBUFFER, framebuffer);
   glGetFramebufferAttachmentParameteriv (GL_FRAMEBUFFER,
                                          framebuffer ? GL_COLOR_ATTACHMENT0
-                                                     : GL_BACK,
+                                                     : GL_BACK_LEFT,
                                          GL_FRAMEBUFFER_ATTACHMENT_RED_SIZE, &size);
 
   if (size > 16)