scene: add wlr_scene_xdg_popup_create

This allows compositors to easily add an xdg_popup to the
scene-graph while retaining the ability to unconstraint the popup
and decide its final position.

Compositors can handle new popups with the wlr_xdg_shell.new_surface
event, get the parent scene-graph node via wlr_xdg_popup.parent.data,
create a new scene-graph node via wlr_scene_xdg_popup_tree_create,
and unconstraint the popup if they want to.

include/wlr/types/wlr_scene.h

@@ -25,6 +25,7 @@
 
 struct wlr_output;
 struct wlr_output_layout;
+struct wlr_xdg_popup;
 
 enum wlr_scene_node_type {
 	WLR_SCENE_NODE_ROOT,
@@ -298,4 +299,11 @@ bool wlr_scene_attach_output_layout(struct wlr_scene *scene,
 struct wlr_scene_node *wlr_scene_subsurface_tree_create(
 	struct wlr_scene_node *parent, struct wlr_surface *surface);
 
+/**
+ * Add a node displaying an xdg_popup and all of its sub-surfaces to the
+ * scene-graph.
+ */
+struct wlr_scene_node *wlr_scene_xdg_popup_create(
+	struct wlr_scene_node *parent, struct wlr_xdg_popup *popup);
+
 #endif

types/meson.build

@@ -10,6 +10,7 @@ wlr_files += files(
 	'scene/subsurface_tree.c',
 	'scene/wlr_scene.c',
 	'scene/output_layout.c',
+	'scene/xdg_shell.c',
 	'seat/wlr_seat_keyboard.c',
 	'seat/wlr_seat_pointer.c',
 	'seat/wlr_seat_touch.c',

types/scene/xdg_shell.c

@@ -0,0 +1,105 @@
+#include <stdlib.h>
+#include <wlr/types/wlr_scene.h>
+#include <wlr/types/wlr_xdg_shell.h>
+
+struct wlr_scene_xdg_popup {
+	struct wlr_scene_tree *tree;
+	struct wlr_xdg_popup *popup;
+	struct wlr_scene_node *surface_node;
+
+	struct wl_listener tree_destroy;
+	struct wl_listener popup_destroy;
+	struct wl_listener popup_map;
+	struct wl_listener popup_unmap;
+	struct wl_listener popup_configure;
+};
+
+static void scene_popup_handle_tree_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_scene_xdg_popup *scene_popup =
+		wl_container_of(listener, scene_popup, tree_destroy);
+	// tree and surface_node will be cleaned up by scene_node_finish
+	wl_list_remove(&scene_popup->tree_destroy.link);
+	wl_list_remove(&scene_popup->popup_destroy.link);
+	free(scene_popup);
+}
+
+static void scene_popup_handle_popup_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_scene_xdg_popup *scene_popup =
+		wl_container_of(listener, scene_popup, popup_destroy);
+	wlr_scene_node_destroy(&scene_popup->tree->node);
+}
+
+static void scene_popup_handle_popup_map(struct wl_listener *listener,
+		void *data) {
+	struct wlr_scene_xdg_popup *scene_popup =
+		wl_container_of(listener, scene_popup, popup_map);
+	wlr_scene_node_set_enabled(&scene_popup->tree->node, true);
+}
+
+static void scene_popup_handle_popup_unmap(struct wl_listener *listener,
+		void *data) {
+	struct wlr_scene_xdg_popup *scene_popup =
+		wl_container_of(listener, scene_popup, popup_unmap);
+	wlr_scene_node_set_enabled(&scene_popup->tree->node, false);
+}
+
+static void scene_popup_update_position(
+		struct wlr_scene_xdg_popup *scene_popup) {
+	double sx, sy;
+	wlr_xdg_popup_get_position(scene_popup->popup, &sx, &sy);
+	wlr_scene_node_set_position(&scene_popup->tree->node, sx, sy);
+}
+
+static void scene_popup_handle_popup_configure(struct wl_listener *listener,
+		void *data) {
+	struct wlr_scene_xdg_popup *scene_popup =
+		wl_container_of(listener, scene_popup, popup_configure);
+	scene_popup_update_position(scene_popup);
+}
+
+struct wlr_scene_node *wlr_scene_xdg_popup_create(
+		struct wlr_scene_node *parent, struct wlr_xdg_popup *popup) {
+	struct wlr_scene_xdg_popup *scene_popup = calloc(1, sizeof(*scene_popup));
+	if (scene_popup == NULL) {
+		return NULL;
+	}
+
+	scene_popup->popup = popup;
+
+	scene_popup->tree = wlr_scene_tree_create(parent);
+	if (scene_popup->tree == NULL) {
+		free(scene_popup);
+		return NULL;
+	}
+
+	scene_popup->surface_node = wlr_scene_subsurface_tree_create(
+		&scene_popup->tree->node, popup->base->surface);
+	if (scene_popup->surface_node == NULL) {
+		wlr_scene_node_destroy(&scene_popup->tree->node);
+		free(scene_popup);
+		return NULL;
+	}
+
+	scene_popup->tree_destroy.notify = scene_popup_handle_tree_destroy;
+	wl_signal_add(&scene_popup->tree->node.events.destroy,
+		&scene_popup->tree_destroy);
+
+	scene_popup->popup_destroy.notify = scene_popup_handle_popup_destroy;
+	wl_signal_add(&popup->base->events.destroy, &scene_popup->popup_destroy);
+
+	scene_popup->popup_map.notify = scene_popup_handle_popup_map;
+	wl_signal_add(&popup->base->events.map, &scene_popup->popup_map);
+
+	scene_popup->popup_unmap.notify = scene_popup_handle_popup_unmap;
+	wl_signal_add(&popup->base->events.unmap, &scene_popup->popup_unmap);
+
+	scene_popup->popup_configure.notify = scene_popup_handle_popup_configure;
+	wl_signal_add(&popup->base->events.configure, &scene_popup->popup_configure);
+
+	wlr_scene_node_set_enabled(&scene_popup->tree->node, popup->base->mapped);
+	scene_popup_update_position(scene_popup);
+
+	return &scene_popup->tree->node;
+}