glx: Implement GLX_EXT_no_config_context (v2)

This more or less ports EGL_KHR_no_config_context to GLX.

v2: Enable the extension only for those backends that support it.

Khronos: https://github.com/KhronosGroup/OpenGL-Registry/pull/102
Reviewed-by: Kenneth Graunke <[email protected]>
Signed-off-by: Adam Jackson <[email protected]>

1 files changed, 26 insertions, 13 deletions

diff --git a/src/glx/create_context.c b/src/glx/create_context.c
index 38e949ab4cd..eab6511ad87 100644
--- a/src/glx/create_context.c
+++ b/src/glx/create_context.c
@@ -47,28 +47,41 @@ 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)
+   if (dpy == NULL)
       return NULL;
 
+   /* Count the number of attributes specified by the application.  All
+    * attributes appear in pairs, except the terminating None.
+    */
+   if (attrib_list != NULL) {
+      for (/* empty */; attrib_list[num_attribs * 2] != 0; num_attribs++)
+	 /* empty */ ;
+   }
+
+   if (cfg) {
+      screen = cfg->screen;
+   } else {
+      int i;
+      for (i = 0; i < num_attribs; i++) {
+         if (attrib_list[i * 2] == GLX_SCREEN)
+            screen = attrib_list[i * 2 + 1];
+      }
+   }
+
    /* 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);
+   psc = GetGLXScreenConfigs(dpy, screen);
    if (psc == NULL)
       return NULL;
 
-   assert(cfg->screen == psc->scr);
+   assert(screen == psc->scr);
 
-   /* Count the number of attributes specified by the application.  All
-    * attributes appear in pairs, except the terminating None.
-    */
-   if (attrib_list != NULL) {
-      for (/* empty */; attrib_list[num_attribs * 2] != 0; num_attribs++)
-	 /* empty */ ;
-   }
+   if (!cfg && !__glXExtensionBitIsEnabled(psc, EXT_no_config_context_bit))
+      return NULL;
 
    if (direct && psc->vtable->create_context_attribs) {
       /* GLX drops the error returned by the driver.  The expectation is that
@@ -104,8 +117,8 @@ 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,