buffer: listen to renderer destroy in wlr_client_buffer

When a renderer is destroyed, so are all textures. Reset the
texture in that case.

include/wlr/types/wlr_buffer.h

@@ -151,6 +151,7 @@ struct wlr_client_buffer {
 	// private state
 
 	struct wl_listener source_destroy;
+	struct wl_listener renderer_destroy;
 
 	size_t n_ignore_locks;
 };

types/buffer/client.c

@@ -25,6 +25,7 @@ static struct wlr_client_buffer *client_buffer_from_buffer(
 static void client_buffer_destroy(struct wlr_buffer *buffer) {
 	struct wlr_client_buffer *client_buffer = client_buffer_from_buffer(buffer);
 	wl_list_remove(&client_buffer->source_destroy.link);
+	wl_list_remove(&client_buffer->renderer_destroy.link);
 	wlr_texture_destroy(client_buffer->texture);
 	free(client_buffer);
 }
@@ -54,6 +55,15 @@ static void client_buffer_handle_source_destroy(struct wl_listener *listener,
 	client_buffer->source = NULL;
 }
 
+static void client_buffer_handle_renderer_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_client_buffer *client_buffer =
+		wl_container_of(listener, client_buffer, renderer_destroy);
+	wl_list_remove(&client_buffer->renderer_destroy.link);
+	wl_list_init(&client_buffer->renderer_destroy.link);
+	client_buffer->texture = NULL;
+}
+
 struct wlr_client_buffer *wlr_client_buffer_create(struct wlr_buffer *buffer,
 		struct wlr_renderer *renderer) {
 	struct wlr_texture *texture = wlr_texture_from_buffer(renderer, buffer);
@@ -75,6 +85,9 @@ struct wlr_client_buffer *wlr_client_buffer_create(struct wlr_buffer *buffer,
 	wl_signal_add(&buffer->events.destroy, &client_buffer->source_destroy);
 	client_buffer->source_destroy.notify = client_buffer_handle_source_destroy;
 
+	wl_signal_add(&texture->renderer->events.destroy, &client_buffer->renderer_destroy);
+	client_buffer->renderer_destroy.notify = client_buffer_handle_renderer_destroy;
+
 	// Ensure the buffer will be released before being destroyed
 	wlr_buffer_lock(&client_buffer->base);
 	wlr_buffer_drop(&client_buffer->base);
@@ -88,6 +101,9 @@ bool wlr_client_buffer_apply_damage(struct wlr_client_buffer *client_buffer,
 		// Someone else still has a reference to the buffer
 		return false;
 	}
+	if (client_buffer->texture == NULL) {
+		return false;
+	}
 
 	return wlr_texture_update_from_buffer(client_buffer->texture, next, damage);
 }