egl: Puts RGBA visuals in the second config selection group.

That way applications don't get windows that are compositor alpha-blended
accidentally.

In the ideal world, this would be done by the xserver, as it does for
GLX, however, an appropriate place could not be found, so it's being
placed here instead.

Fixes: 049f343e8ac "egl: Allow 24-bit visuals for 32-bit RGBA8888 configs"
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67676
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Hal Gentz <zegentzy@protonmail.com>

src/egl/drivers/dri2/platform_x11.c

@@ -831,9 +831,17 @@ dri2_x11_add_configs_for_visuals(struct dri2_egl_display *dri2_dpy,
             dri2_conf = dri2_add_config(disp, config, config_count + 1,
                                         surface_type, config_attrs,
                                         rgba_shifts, rgba_sizes);
-            if (dri2_conf)
+            if (dri2_conf) {
                if (dri2_conf->base.ConfigID == config_count + 1)
                   config_count++;
+
+               /* Put RGBA visuals in the second ConfigSelectGroup so that they
+                * have lower priority. Applications probably don't want the
+                * compositor to alpha-blend their windows.
+                */
+               if (d.data->depth != 24 && d.data->depth != 30)
+                  ++dri2_conf->base.ConfigSelectGroup;
+            }
          }
       }