xF: make highlights request attention from the WM

xF.c

@@ -1158,6 +1158,29 @@ relay_process_response (const struct relay_event_data_response *e)
 
 static void app_buffer_list_ensure_visible (const struct buffer *buffer);
 
+// This could be moved to liberty-xui, but it's somewhat unique to our needs.
+static void
+xui_request_attention (void)
+{
+#ifdef HAVE_X11
+	XEvent xev =
+	{
+		.xclient.type = ClientMessage,
+		.xclient.window = g_xui.x11_window,
+		.xclient.message_type =
+			XInternAtom (g_xui.dpy, "_NET_WM_STATE", False),
+		.xclient.format = 32,
+		.xclient.data.l[0] = 1,  // _NET_WM_STATE_ADD
+		.xclient.data.l[1] =
+			XInternAtom (g_xui.dpy, "_NET_WM_STATE_DEMANDS_ATTENTION", False),
+		.xclient.data.l[3] = 1,  // Source indication: normal
+	};
+	XSendEvent (g_xui.dpy, DefaultRootWindow (g_xui.dpy), False,
+		SubstructureRedirectMask | SubstructureNotifyMask, &xev);
+	XFlush (g_xui.dpy);
+#endif
+}
+
 static struct buffer *
 buffer_find (const char *name)
 {
@@ -1247,6 +1270,7 @@ relay_process_buffer_line (struct buffer *b,
 		&& b->kind == RELAY_BUFFER_KIND_PRIVATE_MESSAGE))
 	{
 		g_xui.ui->beep ();
+		xui_request_attention ();
 		if (!visible)
 			b->highlighted = true;
 	}