some tentative code for _mesa_update_framebuffer_visual()

src/mesa/main/framebuffer.c

@@ -419,6 +419,13 @@ _mesa_update_framebuffer_visual(struct gl_framebuffer *fb)
    _mesa_bzero(&fb->Visual, sizeof(fb->Visual));
    fb->Visual.rgbMode = GL_TRUE; /* assume this */
 
+#if 0 /* this _might_ be needed */
+   if (fb->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
+      /* leave visual fields zero'd */
+      return;
+   }
+#endif
+
    /* find first RGB or CI renderbuffer */
    for (i = 0; i < BUFFER_COUNT; i++) {
       if (fb->Attachment[i].Renderbuffer) {