wayland: switch to separate queue for wp_image_description_v1

f0883cd fixed the issue that
`set_color_management` would be called on every frame, however it didn't
fix the problem that the first frame would have no image description
set.

Due to a lack of blocking here, events would end up happening in the
following order:

    -> wl_surface.commit()
    -> wp_color_management_surface_v1.set_image_description(...)
    -> wl_surface.commit()
    -> wp_color_management_surface_v1.set_image_description(...)

This would mean setting image description would always lag behind by 1
surface commit. This would effectively result in the first frame never
having any image description set.

Fix this by blocking until the compositor processes what's in the queue
and responds with the ready event so we can set the image description.

Author: llyyr

video/out/wayland_common.c

@@ -3452,6 +3452,7 @@ static void set_color_management(struct vo_wayland_state *wl)
         return;
 
     struct pl_color_space color = wl->target_params.color;
+    struct wl_event_queue *cm_queue = NULL;
     int primaries = wl->primaries_map[color.primaries];
     int transfer = wl->transfer_map[color.transfer];
     if (!primaries)
@@ -3489,8 +3490,15 @@ static void set_color_management(struct vo_wayland_state *wl)
         wp_image_description_creator_params_v1_set_max_cll(image_creator_params, lrintf(hdr.max_cll));
         wp_image_description_creator_params_v1_set_max_fall(image_creator_params, lrintf(hdr.max_fall));
     }
+
     struct wp_image_description_v1 *image_description = wp_image_description_creator_params_v1_create(image_creator_params);
+    cm_queue = wl_display_create_queue(wl->display);
+    wl_proxy_set_queue((struct wl_proxy *)image_description, cm_queue);
     wp_image_description_v1_add_listener(image_description, &image_description_listener, wl);
+    /* Block here to ensure the compositor is ready to receive the
+     * image_description before we do anything else. */
+    wl_display_roundtrip_queue(wl->display, cm_queue);
+    wl_event_queue_destroy(cm_queue);
 #endif
 }