Helper: Fix keyboard grabbing in GNOME/Wayland

Refer to:
https://bugzilla.gnome.org/show_bug.cgi?id=783342
https://gitlab.gnome.org/GNOME/mutter/-/commit/5f132f39750f684c3732b4346dec810cd218d609

ChangeLog.md

@@ -35,6 +35,9 @@ automatic WebSocket detection code if an ill-behaved client sent 3 or fewer
 bytes of data immediately after connecting.  Certain versions of Apache
 Guacamole were known to trigger this issue sporadically.
 
+8. The TurboVNC Viewer now works around an issue that prevented keyboard
+grabbing from working when running the viewer in a GNOME/Wayland session.
+
 
 3.1.2
 =====

unix/vncviewer/turbovnchelper.c

@@ -1,4 +1,5 @@
-/* Copyright (C) 2015-2019, 2021-2022 D. R. Commander.  All Rights Reserved.
+/* Copyright (C) 2015-2019, 2021-2022, 2024 D. R. Commander.
+ *                                          All Rights Reserved.
  *
  * This is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -227,6 +228,28 @@ JNIEXPORT void JNICALL Java_com_turbovnc_vncviewer_Viewport_x11FullScreen
 }
 
 
+/*
+ * Allow/disallow keyboard grabbing when using GNOME/Wayland.
+ */
+
+static void xwayland_grab_keyboard(Display *dpy, Window win, int on)
+{
+  XEvent e;
+  Atom _XWAYLAND_MAY_GRAB_KEYBOARD =
+    XInternAtom(dpy, "_XWAYLAND_MAY_GRAB_KEYBOARD", False);
+
+  memset(&e, 0, sizeof(e));
+  e.xclient.type = ClientMessage;
+  e.xclient.message_type = _XWAYLAND_MAY_GRAB_KEYBOARD;
+  e.xclient.display = dpy;
+  e.xclient.window = win;
+  e.xclient.format = 32;
+  e.xclient.data.l[0] = on;
+
+  XSendEvent(dpy, DefaultRootWindow(dpy), False, SubstructureRedirectMask, &e);
+}
+
+
 JNIEXPORT void JNICALL Java_com_turbovnc_vncviewer_Viewport_grabKeyboard
   (JNIEnv *env, jobject obj, jboolean on, jboolean pointer)
 {
@@ -261,6 +284,7 @@ JNIEXPORT void JNICALL Java_com_turbovnc_vncviewer_Viewport_grabKeyboard
     THROW("Could not get X11 drawing surface info");
 
   XSync(x11dsi->display, False);
+  xwayland_grab_keyboard(x11dsi->display, x11dsi->drawable, on);
   if (on) {
     int count = 5;