+ if (cfg) {
+ screen = cfg->screen;
+ } else {
+ for (unsigned int i = 0; i < num_attribs; i++) {
+ if (attrib_list[i * 2] == GLX_SCREEN)
+ screen = attrib_list[i * 2 + 1];
+ }
+ if (screen == -1) {
+ __glXSendError(dpy, BadValue, 0, X_GLXCreateContextAttribsARB, True);
+ return NULL;
+ }
+ }
+
+ /* This means that either the caller passed the wrong display pointer or
+ * one of the internal GLX data structures (probably the fbconfig) has an
+ * error. There is nothing sensible to do, so return an error.
+ */
+ psc = GetGLXScreenConfigs(dpy, screen);
+ if (psc == NULL)
+ return NULL;
+
+ assert(screen == psc->scr);
+