node.c: add helpers for returning structs from node data

Support returning the following structs:
  - view from LAB_NODE_DESC_VIEW or LAB_NODE_DESC_XDG_POPUP
  - lab_layer_surface form LAB_NODE_DESC_LAYER_SURFACE
  - lab_layer_popup from LAB_NODE_DESC_LAYER_POPUP

include/node.h

@@ -3,12 +3,16 @@
 #define __LABWC_NODE_DESCRIPTOR_H
 #include <wlr/types/wlr_scene.h>
 
+struct view;
+struct lab_layer_surface;
+struct lab_layer_popup;
+
 enum node_descriptor_type {
 	LAB_NODE_DESC_NODE = 0,
-	LAB_NODE_DESC_VIEW,		/* *data --> struct view */
+	LAB_NODE_DESC_VIEW,
-	LAB_NODE_DESC_XDG_POPUP,	/* *data --> struct view */
+	LAB_NODE_DESC_XDG_POPUP,
-	LAB_NODE_DESC_LAYER_SURFACE,	/* *data --> struct lab_layer_surface */
+	LAB_NODE_DESC_LAYER_SURFACE,
-	LAB_NODE_DESC_LAYER_POPUP,	/* *data --> struct lab_layer_popup */
+	LAB_NODE_DESC_LAYER_POPUP,
 };
 
 struct node_descriptor {
@@ -17,7 +21,37 @@ struct node_descriptor {
 	struct wl_listener destroy;
 };
 
-void node_descriptor_create(struct wlr_scene_node *node,
+/**
+ * node_descriptor_create - create node descriptor for wlr_scene_node user_data
+ * @scene_node: wlr_scene_node to attached node_descriptor to
+ * @type: node descriptor type
+ * @data: struct to point to as follows:
+ *   - LAB_NODE_DESC_VIEW		struct view
+ *   - LAB_NODE_DESC_XDG_POPUP		struct view
+ *   - LAB_NODE_DESC_LAYER_SURFACE	struct lab_layer_surface
+ *   - LAB_NODE_DESC_LAYER_POPUP	struct lab_layer_popup
+ */
+void node_descriptor_create(struct wlr_scene_node *scene_node,
 	enum node_descriptor_type type, void *data);
 
+/**
+ * node_view_from_node - return view struct from node
+ * @node_descriptor: node_descriptor from which to return data
+ */
+struct view *node_view_from_node(struct node_descriptor *node_descriptor);
+
+/**
+ * node_lab_surface_from_node - return lab_layer_surface struct from node
+ * @node_descriptor: node_descriptor from which to return data
+ */
+struct lab_layer_surface *node_layer_surface_from_node(
+	struct node_descriptor *node_descriptor);
+
+/**
+ * node_layer_popup_from_node - return lab_layer_popup struct from node
+ * @node_descriptor: node_descriptor from which to return data
+ */
+struct lab_layer_popup *node_layer_popup_from_node(
+	struct node_descriptor *node_descriptor);
+
 #endif /* __LABWC_NODE_DESCRIPTOR_H */

src/debug.c

@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0-only
-#include <assert.h>
 #include <wlr/types/wlr_layer_shell_v1.h>
 #include <wlr/types/wlr_scene.h>
 #include "buffer.h"
@@ -113,10 +112,7 @@ get_special(struct server *server, struct wlr_scene_node *node,
 		return "server->view_tree";
 	}
 	if (node->parent == &server->view_tree->node) {
-		struct node_descriptor *desc = node->data;
+		*last_view = node_view_from_node(node->data);
-		assert(desc->type == LAB_NODE_DESC_VIEW
-			|| desc->type == LAB_NODE_DESC_XDG_POPUP);
-		*last_view = desc->data;
 	}
 	const char *view_part = get_view_part(*last_view, node);
 	if (view_part) {

src/node.c

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <assert.h>
 #include <stdlib.h>
 #include "node.h"
 
@@ -21,7 +22,7 @@ destroy_notify(struct wl_listener *listener, void *data)
 }
 
 void
-node_descriptor_create(struct wlr_scene_node *node,
+node_descriptor_create(struct wlr_scene_node *scene_node,
 		enum node_descriptor_type type, void *data)
 {
 	struct node_descriptor *node_descriptor =
@@ -32,6 +33,28 @@ node_descriptor_create(struct wlr_scene_node *node,
 	node_descriptor->type = type;
 	node_descriptor->data = data;
 	node_descriptor->destroy.notify = destroy_notify;
-	wl_signal_add(&node->events.destroy, &node_descriptor->destroy);
+	wl_signal_add(&scene_node->events.destroy, &node_descriptor->destroy);
-	node->data = node_descriptor;
+	scene_node->data = node_descriptor;
+}
+
+struct view *
+node_view_from_node(struct node_descriptor *node_descriptor)
+{
+	assert(node_descriptor->type == LAB_NODE_DESC_VIEW
+		|| node_descriptor->type == LAB_NODE_DESC_XDG_POPUP);
+	return (struct view *)node_descriptor->data;
+}
+
+struct lab_layer_surface *
+node_layer_surface_from_node(struct node_descriptor *node_descriptor)
+{
+	assert(node_descriptor->type == LAB_NODE_DESC_LAYER_SURFACE);
+	return (struct lab_layer_surface *)node_descriptor->data;
+}
+
+struct lab_layer_popup *
+node_layer_popup_from_node(struct node_descriptor *node_descriptor)
+{
+	assert(node_descriptor->type == LAB_NODE_DESC_LAYER_POPUP);
+	return (struct lab_layer_popup *)node_descriptor->data;
 }