scene: add wlr_scene_attach_output_layout

This is a helper to integrate wlr_scene with wlr_output_layout.

include/wlr/types/wlr_scene.h

@@ -24,6 +24,7 @@
 #include <wlr/types/wlr_surface.h>
 
 struct wlr_output;
+struct wlr_output_layout;
 
 enum wlr_scene_node_type {
 	WLR_SCENE_NODE_ROOT,
@@ -203,4 +204,13 @@ void wlr_scene_output_set_position(struct wlr_scene_output *scene_output,
  */
 bool wlr_scene_output_commit(struct wlr_scene_output *scene_output);
 
+/**
+ * Attach an output layout to a scene.
+ *
+ * Outputs in the output layout are automatically added to the scene. Any
+ * change to the output layout is mirrored to the scene-graph outputs.
+ */
+bool wlr_scene_attach_output_layout(struct wlr_scene *scene,
+	struct wlr_output_layout *output_layout);
+
 #endif

types/meson.build

@@ -4,6 +4,7 @@ wlr_files += files(
 	'data_device/wlr_data_source.c',
 	'data_device/wlr_drag.c',
 	'scene/wlr_scene.c',
+	'scene/output_layout.c',
 	'seat/wlr_seat_keyboard.c',
 	'seat/wlr_seat_pointer.c',
 	'seat/wlr_seat_touch.c',

types/scene/output_layout.c

@@ -0,0 +1,105 @@
+#include <stdlib.h>
+#include <wlr/types/wlr_output_layout.h>
+#include <wlr/types/wlr_scene.h>
+
+struct wlr_scene_output_layout {
+	struct wlr_output_layout *layout;
+	struct wlr_scene *scene;
+
+	struct wl_listener layout_add;
+	struct wl_listener layout_change;
+	struct wl_listener layout_destroy;
+	struct wl_listener scene_destroy;
+};
+
+static void scene_output_layout_destroy(struct wlr_scene_output_layout *sol) {
+	wl_list_remove(&sol->layout_destroy.link);
+	wl_list_remove(&sol->layout_add.link);
+	wl_list_remove(&sol->layout_change.link);
+	wl_list_remove(&sol->scene_destroy.link);
+	free(sol);
+}
+
+static void scene_output_layout_handle_layout_destroy(
+		struct wl_listener *listener, void *data) {
+	struct wlr_scene_output_layout *sol =
+		wl_container_of(listener, sol, layout_destroy);
+
+	// Remove all outputs managed by the output layout
+	struct wlr_scene_output *scene_output, *tmp;
+	wl_list_for_each_safe(scene_output, tmp, &sol->scene->outputs, link) {
+		struct wlr_output_layout_output *lo =
+			wlr_output_layout_get(sol->layout, scene_output->output);
+		if (lo != NULL) {
+			wlr_scene_output_destroy(scene_output);
+		}
+	}
+
+	scene_output_layout_destroy(sol);
+}
+
+static void scene_output_layout_handle_layout_change(
+		struct wl_listener *listener, void *data) {
+	struct wlr_scene_output_layout *sol =
+		wl_container_of(listener, sol, layout_change);
+
+	struct wlr_scene_output *scene_output, *tmp;
+	wl_list_for_each_safe(scene_output, tmp, &sol->scene->outputs, link) {
+		struct wlr_output_layout_output *lo =
+			wlr_output_layout_get(sol->layout, scene_output->output);
+		if (lo == NULL) {
+			// Output has been removed from the layout
+			wlr_scene_output_destroy(scene_output);
+			continue;
+		}
+
+		wlr_scene_output_set_position(scene_output, lo->x, lo->y);
+	}
+}
+
+static void scene_output_layout_handle_layout_add(
+		struct wl_listener *listener, void *data) {
+	struct wlr_scene_output_layout *sol =
+		wl_container_of(listener, sol, layout_add);
+	struct wlr_output_layout_output *lo = data;
+
+	struct wlr_scene_output *scene_output =
+		wlr_scene_output_create(sol->scene, lo->output);
+	if (scene_output == NULL) {
+		return;
+	}
+
+	wlr_scene_output_set_position(scene_output, lo->x, lo->y);
+}
+
+static void scene_output_layout_handle_scene_destroy(
+		struct wl_listener *listener, void *data) {
+	struct wlr_scene_output_layout *sol =
+		wl_container_of(listener, sol, scene_destroy);
+	scene_output_layout_destroy(sol);
+}
+
+bool wlr_scene_attach_output_layout(struct wlr_scene *scene,
+		struct wlr_output_layout *output_layout) {
+	struct wlr_scene_output_layout *sol = calloc(1, sizeof(*sol));
+	if (sol == NULL) {
+		return false;
+	}
+
+	sol->scene = scene;
+	sol->layout = output_layout;
+
+	sol->layout_destroy.notify = scene_output_layout_handle_layout_destroy;
+	wl_signal_add(&output_layout->events.destroy, &sol->layout_destroy);
+
+	sol->layout_change.notify = scene_output_layout_handle_layout_change;
+	wl_signal_add(&output_layout->events.change, &sol->layout_change);
+
+	sol->layout_add.notify = scene_output_layout_handle_layout_add;
+	wl_signal_add(&output_layout->events.add, &sol->layout_add);
+
+	sol->scene_destroy.notify = scene_output_layout_handle_scene_destroy;
+	wl_signal_add(&output_layout->events.destroy, &sol->scene_destroy);
+
+	return true;
+}