improve xdg + layer shell support

node.c

@@ -34,4 +34,34 @@ struct diyac_view *diyac_view_from_node(struct wlr_scene_node *wlr_scene_node)
     struct diyac_node_descriptor *node_descriptor = wlr_scene_node->data;
     assert(node_descriptor->type == DIYAC_NODE_VIEW || node_descriptor->type == DIYAC_NODE_XDG_POPUP);
     return (struct diyac_view *)node_descriptor->data;
+}
+
+struct diyac_node_descriptor * diyac_node_at(struct diyac_server* server, double lx, double ly, struct wlr_surface **surface, double *sx, double *sy)
+{
+    /* This returns the topmost node in the scene at the given layout coords.
+     * We only care about surface nodes as we are specifically looking for a
+     * surface in the surface tree of a diyac_view. */
+    struct wlr_scene_node *node = wlr_scene_node_at(
+        &server->scene->tree.node, lx, ly, sx, sy);
+    if (node == NULL || node->type != WLR_SCENE_NODE_BUFFER)
+    {
+        return NULL;
+    }
+    struct wlr_scene_buffer *scene_buffer = wlr_scene_buffer_from_node(node);
+    struct wlr_scene_surface *scene_surface =
+        wlr_scene_surface_try_from_buffer(scene_buffer);
+    if (!scene_surface)
+    {
+        return NULL;
+    }
+
+    *surface = scene_surface->surface;
+    /* Find the node corresponding to the diyac_view at the root of this
+     * surface tree, it is the only one for which we set the data field. */
+    struct wlr_scene_tree *tree = node->parent;
+    while (tree != NULL && tree->node.data == NULL)
+    {
+        tree = tree->node.parent;
+    }
+    return tree->node.data;
 }