backend/headless: handle renderer destroy

When the headless backend uses an already-existing renderer, it doesn't
have ownership over the renderer. When the renderer is destroyed, the
headless backend needs to destroy itself.

backend/headless/backend.c

@@ -47,6 +47,7 @@ static void backend_destroy(struct wlr_backend *wlr_backend) {
 	}
 
 	wl_list_remove(&backend->display_destroy.link);
+	wl_list_remove(&backend->renderer_destroy.link);
 
 	struct wlr_headless_output *output, *output_tmp;
 	wl_list_for_each_safe(output, output_tmp, &backend->outputs, link) {
@@ -61,8 +62,8 @@ static void backend_destroy(struct wlr_backend *wlr_backend) {
 
 	wlr_signal_emit_safe(&wlr_backend->events.destroy, backend);
 
-	wlr_renderer_destroy(backend->renderer);
 	if (backend->egl == &backend->priv_egl) {
+		wlr_renderer_destroy(backend->renderer);
 		wlr_egl_finish(&backend->priv_egl);
 	}
 	free(backend);
@@ -87,6 +88,12 @@ static void handle_display_destroy(struct wl_listener *listener, void *data) {
 	backend_destroy(&backend->backend);
 }
 
+static void handle_renderer_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_headless_backend *backend =
+		wl_container_of(listener, backend, renderer_destroy);
+	backend_destroy(&backend->backend);
+}
+
 static bool backend_init(struct wlr_headless_backend *backend,
 		struct wl_display *display, struct wlr_renderer *renderer) {
 	wlr_backend_init(&backend->backend, &backend_impl);
@@ -112,6 +119,8 @@ static bool backend_init(struct wlr_headless_backend *backend,
 	backend->display_destroy.notify = handle_display_destroy;
 	wl_display_add_destroy_listener(display, &backend->display_destroy);
 
+	wl_list_init(&backend->renderer_destroy.link);
+
 	return true;
 }
 
@@ -173,6 +182,9 @@ struct wlr_backend *wlr_headless_backend_create_with_renderer(
 		return NULL;
 	}
 
+	backend->renderer_destroy.notify = handle_renderer_destroy;
+	wl_signal_add(&renderer->events.destroy, &backend->renderer_destroy);
+
 	return &backend->backend;
 }
 

include/backend/headless.h

@@ -17,6 +17,7 @@ struct wlr_headless_backend {
 	size_t last_output_num;
 	struct wl_list input_devices;
 	struct wl_listener display_destroy;
+	struct wl_listener renderer_destroy;
 	bool started;
 	GLenum internal_format;
 };