Add node-descriptor for wlr_scene_nodes

Support identification of wlr_scene_node role to enable simplification
of codebase including the avoidance of iterating over lists of
layer-surface, menuitems, and so on.

Use node-descriptors for xdg toplevels and popups

include/node-descriptor.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __LABWC_NODE_DESCRIPTOR_H
+#define __LABWC_NODE_DESCRIPTOR_H
+#include <wlr/types/wlr_scene.h>
+
+enum node_descriptor_type {
+	LAB_NODE_DESC_NODE = 0,
+	LAB_NODE_DESC_VIEW,		/* *data --> struct view */
+	LAB_NODE_DESC_XDG_POPUP,	/* *data --> struct view */
+	LAB_NODE_DESC_LAYER_SURFACE,	/* *data --> struct lab_layer_surface */
+	LAB_NODE_DESC_LAYER_POPUP,	/* *data --> struct lab_layer_popup */
+};
+
+struct node_descriptor {
+	enum node_descriptor_type type;
+	void *data;
+	struct wl_listener destroy;
+};
+
+void node_descriptor_create(struct wlr_scene_node *node,
+	enum node_descriptor_type type, void *data);
+
+#endif /* __LABWC_NODE_DESCRIPTOR_H */

src/desktop.c

@@ -3,6 +3,7 @@
 #include <assert.h>
 #include "labwc.h"
 #include "layers.h"
+#include "node-descriptor.h"
 #include "ssd.h"
 
 static void
@@ -285,7 +286,21 @@ desktop_node_and_view_at(struct server *server, double lx, double ly,
 	}
 	struct wlr_scene_node *osd = &server->osd_tree->node;
 	struct wlr_scene_node *menu = &server->menu_tree->node;
-	while (node && !node->data) {
+	while (node) {
+		struct node_descriptor *desc = node->data;
+		if (desc) {
+			if (desc->type == LAB_NODE_DESC_VIEW) {
+				goto has_view_data;
+			}
+			if (desc->type == LAB_NODE_DESC_XDG_POPUP) {
+				goto has_view_data;
+			}
+			if (desc->type == LAB_NODE_DESC_LAYER_POPUP) {
+				/* FIXME: we shouldn't have to set *view_area */
+				*view_area = LAB_SSD_LAYER_SURFACE;
+				return NULL;
+			}
+		}
 		if (node == osd) {
 			*view_area = LAB_SSD_OSD;
 			return NULL;
@@ -297,10 +312,13 @@ desktop_node_and_view_at(struct server *server, double lx, double ly,
 	}
 	if (!node) {
 		wlr_log(WLR_ERROR, "Unknown node detected");
-		*view_area = LAB_SSD_NONE;
-		return NULL;
 	}
-	struct view *view = node->data;
+	*view_area = LAB_SSD_NONE;
+	return NULL;
+
+has_view_data:
+	struct node_descriptor *desc = node->data;
+	struct view *view = desc->data;
 	*view_area = ssd_get_part_type(view, *scene_node);
 	return view;
 }

src/meson.build

@@ -11,6 +11,7 @@ labwc_sources = files(
   'key-state.c',
   'layers.c',
   'main.c',
+  'node-descriptor.c',
   'osd.c',
   'output.c',
   'resistance.c',

src/node-descriptor.c

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <stdlib.h>
+#include "node-descriptor.h"
+
+static void
+descriptor_destroy(struct node_descriptor *node_descriptor)
+{
+	if (!node_descriptor) {
+		return;
+	}
+	wl_list_remove(&node_descriptor->destroy.link);
+	free(node_descriptor);
+}
+
+static void
+destroy_notify(struct wl_listener *listener, void *data)
+{
+	struct node_descriptor *node_descriptor =
+		wl_container_of(listener, node_descriptor, destroy);
+	descriptor_destroy(node_descriptor);
+}
+
+void
+node_descriptor_create(struct wlr_scene_node *node,
+		enum node_descriptor_type type, void *data)
+{
+	struct node_descriptor *node_descriptor =
+		calloc(1, sizeof(struct node_descriptor));
+	if (!node_descriptor) {
+		return;
+	}
+	node_descriptor->type = type;
+	node_descriptor->data = data;
+	node_descriptor->destroy.notify = destroy_notify;
+	wl_signal_add(&node->events.destroy, &node_descriptor->destroy);
+	node->data = node_descriptor;
+}

src/xdg-popup.c

@@ -8,6 +8,7 @@
  */
 
 #include "labwc.h"
+#include "node-descriptor.h"
 
 struct view_child {
 	struct wlr_surface *surface;
@@ -93,6 +94,8 @@ xdg_popup_create(struct view *view, struct wlr_xdg_popup *wlr_popup)
 	struct wlr_scene_node *parent_node = parent->surface->data;
 	wlr_popup->base->surface->data =
 		wlr_scene_xdg_surface_create(parent_node, wlr_popup->base);
+	node_descriptor_create(wlr_popup->base->surface->data,
+		LAB_NODE_DESC_XDG_POPUP, view);
 
 	popup_unconstrain(view, wlr_popup);
 }

src/xdg.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <assert.h>
 #include "labwc.h"
+#include "node-descriptor.h"
 #include "ssd.h"
 
 static void
@@ -404,7 +405,8 @@ xdg_surface_new(struct wl_listener *listener, void *data)
 		wl_resource_post_no_memory(view->surface->resource);
 		return;
 	}
-	view->scene_tree->node.data = view;
+	node_descriptor_create(&view->scene_tree->node,
+		LAB_NODE_DESC_VIEW, view);
 
 	/* In support of xdg_toplevel_decoration */
 	xdg_surface->data = view;

src/xwayland.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <assert.h>
 #include "labwc.h"
+#include "node-descriptor.h"
 #include "ssd.h"
 
 static void
@@ -394,7 +395,8 @@ xwayland_surface_new(struct wl_listener *listener, void *data)
 	view->xwayland_surface = xsurface;
 
 	view->scene_tree = wlr_scene_tree_create(&view->server->view_tree->node);
-	view->scene_tree->node.data = view;
+	node_descriptor_create(&view->scene_tree->node,
+		LAB_NODE_DESC_VIEW, view);
 	xsurface->data = view;
 
 	view->map.notify = handle_map;