xwayland: terminate when no client is connected

Automatically shutdown Xwayland 10s after all X11 clients have
gone away.

include/xwayland/xwm.h

@@ -122,6 +122,7 @@ struct wlr_xwm {
 
 	const xcb_query_extension_reply_t *xfixes;
 	const xcb_query_extension_reply_t *xres;
+	uint32_t xfixes_major_version;
 #if HAS_XCB_ERRORS
 	xcb_errors_context_t *errors_context;
 #endif

xwayland/meson.build

@@ -74,3 +74,9 @@ wlr_files += files(
 )
 wlr_deps += xwayland_libs
 features += { 'xwayland': true }
+
+have = cc.has_function('xcb_xfixes_set_client_disconnect_mode', dependencies: xwayland_libs)
+add_project_arguments(
+	'-DHAS_XCB_XFIXES_SET_CLIENT_DISCONNECT_MODE=@0@'.format(have.to_int()),
+	language: 'c',
+)

xwayland/xwayland.c

@@ -88,6 +88,9 @@ struct wlr_xwayland *wlr_xwayland_create(struct wl_display *wl_display,
 	struct wlr_xwayland_server_options options = {
 		.lazy = lazy,
 		.enable_wm = true,
+#if HAS_XCB_XFIXES_SET_CLIENT_DISCONNECT_MODE
+		.terminate_delay = lazy ? 10 : 0,
+#endif
 	};
 	xwayland->server = wlr_xwayland_server_create(wl_display, &options);
 	if (xwayland->server == NULL) {

xwayland/xwm.c

@@ -1842,6 +1842,7 @@ static void xwm_get_resources(struct wlr_xwm *xwm) {
 
 	wlr_log(WLR_DEBUG, "xfixes version: %" PRIu32 ".%" PRIu32,
 		xfixes_reply->major_version, xfixes_reply->minor_version);
+	xwm->xfixes_major_version = xfixes_reply->major_version;
 
 	free(xfixes_reply);
 
@@ -2103,6 +2104,14 @@ struct wlr_xwm *xwm_create(struct wlr_xwayland *xwayland, int wm_fd) {
 		sizeof(supported)/sizeof(*supported),
 		supported);
 
+#if HAS_XCB_XFIXES_SET_CLIENT_DISCONNECT_MODE
+	if (xwm->xwayland->server->options.terminate_delay > 0 &&
+			xwm->xfixes_major_version >= 6) {
+		xcb_xfixes_set_client_disconnect_mode(xwm->xcb_conn,
+			XCB_XFIXES_CLIENT_DISCONNECT_FLAGS_TERMINATE);
+	}
+#endif
+
 	xcb_flush(xwm->xcb_conn);
 
 	xwm_set_net_active_window(xwm, XCB_WINDOW_NONE);