wlr_scene: Add drag icon helper

include/wlr/types/wlr_scene.h

@@ -28,6 +28,7 @@ struct wlr_output;
 struct wlr_output_layout;
 struct wlr_xdg_surface;
 struct wlr_layer_surface_v1;
+struct wlr_drag_icon;
 
 struct wlr_scene_node;
 struct wlr_scene_buffer;
@@ -472,4 +473,11 @@ void wlr_scene_layer_surface_v1_configure(
 	struct wlr_scene_layer_surface_v1 *scene_layer_surface,
 	const struct wlr_box *full_area, struct wlr_box *usable_area);
 
+/**
+ * Add a node displaying a drag icon and all its sub-surfaces to the
+ * scene-graph.
+ */
+struct wlr_scene_tree *wlr_scene_drag_icon_create(
+	struct wlr_scene_tree *parent, struct wlr_drag_icon *drag_icon);
+
 #endif

types/meson.build

@@ -8,6 +8,7 @@ wlr_files += files(
 	'output/render.c',
 	'output/state.c',
 	'output/transform.c',
+	'scene/drag_icon.c',
 	'scene/subsurface_tree.c',
 	'scene/surface.c',
 	'scene/wlr_scene.c',

types/scene/drag_icon.c

@@ -0,0 +1,93 @@
+#include <stdlib.h>
+#include <wlr/types/wlr_scene.h>
+#include <wlr/types/wlr_data_device.h>
+
+struct wlr_scene_drag_icon {
+	struct wlr_scene_tree *tree;
+	struct wlr_scene_tree *surface_tree;
+	struct wlr_drag_icon *drag_icon;
+
+	struct wl_listener tree_destroy;
+	struct wl_listener drag_icon_surface_commit;
+	struct wl_listener drag_icon_map;
+	struct wl_listener drag_icon_unmap;
+	struct wl_listener drag_icon_destroy;
+};
+
+static void drag_icon_handle_surface_commit(struct wl_listener *listener, void *data) {
+	struct wlr_scene_drag_icon *icon =
+		wl_container_of(listener, icon, drag_icon_surface_commit);
+	struct wlr_surface *surface = icon->drag_icon->surface;
+	wlr_scene_node_set_position(&icon->surface_tree->node,
+		surface->sx, surface->sy);
+}
+
+static void drag_icon_handle_map(struct wl_listener *listener, void *data) {
+	struct wlr_scene_drag_icon *icon =
+		wl_container_of(listener, icon, drag_icon_map);
+	wlr_scene_node_set_enabled(&icon->tree->node, true);
+}
+
+static void drag_icon_handle_unmap(struct wl_listener *listener, void *data) {
+	struct wlr_scene_drag_icon *icon =
+		wl_container_of(listener, icon, drag_icon_unmap);
+	wlr_scene_node_set_enabled(&icon->tree->node, false);
+}
+
+static void drag_icon_handle_tree_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_scene_drag_icon *icon =
+		wl_container_of(listener, icon, tree_destroy);
+	wl_list_remove(&icon->tree_destroy.link);
+	wl_list_remove(&icon->drag_icon_surface_commit.link);
+	wl_list_remove(&icon->drag_icon_map.link);
+	wl_list_remove(&icon->drag_icon_unmap.link);
+	wl_list_remove(&icon->drag_icon_destroy.link);
+	free(icon);
+}
+
+static void drag_icon_handle_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_scene_drag_icon *icon =
+		wl_container_of(listener, icon, drag_icon_destroy);
+	wlr_scene_node_destroy(&icon->tree->node);
+}
+
+struct wlr_scene_tree *wlr_scene_drag_icon_create(
+		struct wlr_scene_tree *parent, struct wlr_drag_icon *drag_icon) {
+	struct wlr_scene_drag_icon *icon = calloc(1, sizeof(*icon));
+	if (!icon) {
+		return NULL;
+	}
+
+	icon->drag_icon = drag_icon;
+
+	icon->tree = wlr_scene_tree_create(parent);
+	if (!icon->tree) {
+		free(icon);
+		return NULL;
+	}
+
+	icon->surface_tree = wlr_scene_subsurface_tree_create(
+		icon->tree, drag_icon->surface);
+	if (!icon->surface_tree) {
+		wlr_scene_node_destroy(&icon->tree->node);
+		free(icon);
+		return NULL;
+	}
+
+	wlr_scene_node_set_position(&icon->surface_tree->node,
+		drag_icon->surface->sx, drag_icon->surface->sy);
+	wlr_scene_node_set_enabled(&icon->tree->node, drag_icon->mapped);
+
+	icon->tree_destroy.notify = drag_icon_handle_tree_destroy;
+	wl_signal_add(&icon->tree->node.events.destroy, &icon->tree_destroy);
+	icon->drag_icon_surface_commit.notify = drag_icon_handle_surface_commit;
+	wl_signal_add(&drag_icon->surface->events.commit, &icon->drag_icon_surface_commit);
+	icon->drag_icon_map.notify = drag_icon_handle_map;
+	wl_signal_add(&drag_icon->events.map, &icon->drag_icon_map);
+	icon->drag_icon_unmap.notify = drag_icon_handle_unmap;
+	wl_signal_add(&drag_icon->events.unmap, &icon->drag_icon_unmap);
+	icon->drag_icon_destroy.notify = drag_icon_handle_destroy;
+	wl_signal_add(&drag_icon->events.destroy, &icon->drag_icon_destroy);
+
+	return icon->tree;
+}