glx: move dri2 init checks to separate function

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30375>

src/glx/dri2_glx.c

@@ -1170,6 +1170,21 @@ dri2GetGlxDrawableFromXDrawableId(Display *dpy, XID id)
    return NULL;
 }
 
+bool
+dri2CheckSupport(Display *dpy)
+{
+   int eventBase, errorBase;
+   int driMajor, driMinor;
+
+   if (!DRI2QueryExtension(dpy, &eventBase, &errorBase))
+      return false;
+   if (!DRI2QueryVersion(dpy, &driMajor, &driMinor) ||
+       driMinor < 3) {
+      return false;
+   }
+   return true;
+}
+
 /*
  * Allocate, initialize and return a __DRIdisplayPrivate object.
  * This is called from __glXInitialize() when we are given a new
@@ -1179,22 +1194,13 @@ _X_HIDDEN __GLXDRIdisplay *
 dri2CreateDisplay(Display * dpy)
 {
    struct dri2_display *pdp;
-   int eventBase, errorBase, i;
-   int driMajor, driMinor;
-
-   if (!DRI2QueryExtension(dpy, &eventBase, &errorBase))
-      return NULL;
-   if (!DRI2QueryVersion(dpy, &driMajor, &driMinor) ||
-       driMinor < 3) {
-      return NULL;
-   }
 
    pdp = malloc(sizeof *pdp);
    if (pdp == NULL)
       return NULL;
 
 
-   i = 0;
+   int i = 0;
    pdp->loader_extensions[i++] = &dri2LoaderExtension.base;
    pdp->loader_extensions[i++] = &dri2UseInvalidate.base;
    pdp->loader_extensions[i++] = &driBackgroundCallable.base;

src/glx/glxclient.h

@@ -150,6 +150,7 @@ struct glx_screen *dri3_create_screen(int screen, struct glx_display * priv, boo
 void dri3_destroy_display(__GLXDRIdisplay * dpy);
 #endif
 
+bool dri2CheckSupport(Display *dpy);
 struct glx_screen *dri2CreateScreen(int screen, struct glx_display * priv, bool driver_name_is_inferred);
 void dri2DestroyDisplay(__GLXDRIdisplay * dpy);
 

src/glx/glxext.c

@@ -797,7 +797,7 @@ AllocAndFetchScreenConfigs(Display * dpy, struct glx_display * priv, enum glx_dr
       }
 #endif /* HAVE_DRI3 */
 #if defined(HAVE_X11_DRI2)
-      if (psc == NULL && glx_driver & GLX_DRIVER_DRI2) {
+      if (psc == NULL && glx_driver & GLX_DRIVER_DRI2 && dri2CheckSupport(dpy)) {
          priv->dri2Display = dri2CreateDisplay(dpy);
 	      psc = dri2CreateScreen(i, priv, driver_name_is_inferred);
          if (psc)