1 files changed, 35 insertions, 14 deletions

diff --git a/src/glx/create_context.c b/src/glx/create_context.c
index 38e949ab4cd..fa15d551af0 100644
--- a/src/glx/create_context.c
+++ b/src/glx/create_context.c
@@ -33,6 +33,14 @@
 #error This code requires sizeof(uint32_t) == sizeof(int).
 #endif
 
+/* debian stretch still has ancient headers and we're apparently still
+ * using that for gitlab ci. please delete me when that's fixed.
+ */
+#ifndef X_GLXCreateContextAttribsARB
+#warning Please update your GLX protocol headers
+#define X_GLXCreateContextAttribsARB 34
+#endif
+
 _X_HIDDEN GLXContext
 glXCreateContextAttribsARB(Display *dpy, GLXFBConfig config,
 			   GLXContext share_context, Bool direct,
@@ -47,21 +55,11 @@ glXCreateContextAttribsARB(Display *dpy, GLXFBConfig config,
    xcb_generic_error_t *err;
    xcb_void_cookie_t cookie;
    unsigned dummy_err = 0;
+   int screen = -1;
 
-
-   if (dpy == NULL || cfg == NULL)
-      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, cfg->screen);
-   if (psc == NULL)
+   if (dpy == NULL)
       return NULL;
 
-   assert(cfg->screen == psc->scr);
-
    /* Count the number of attributes specified by the application.  All
     * attributes appear in pairs, except the terminating None.
     */
@@ -70,6 +68,29 @@ glXCreateContextAttribsARB(Display *dpy, GLXFBConfig config,
 	 /* empty */ ;
    }
 
+   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);
+
    if (direct && psc->vtable->create_context_attribs) {
       /* GLX drops the error returned by the driver.  The expectation is that
        * an error will also be returned by the server.  The server's error
@@ -104,8 +125,8 @@ glXCreateContextAttribsARB(Display *dpy, GLXFBConfig config,
    cookie =
       xcb_glx_create_context_attribs_arb_checked(c,
 						 gc->xid,
-						 cfg->fbconfigID,
-						 cfg->screen,
+						 cfg ? cfg->fbconfigID : 0,
+						 screen,
 						 gc->share_xid,
 						 gc->isDirect,
 						 num_attribs,