Force X11 transient windows to be dialog type (no taskbar entry)

source/backend/plugin/CarlaPluginUi.cpp

@@ -277,7 +277,13 @@ bool CarlaPluginUi::tryTransientWinIdMatch(const ulong pid, const char* const ui
     if (lastGoodWindow == 0)
         return false;
 
+    Atom _nwt = XInternAtom(sd.display ,"_NET_WM_WINDOW_TYPE", True);
+    Atom _nwd = XInternAtom(sd.display, "_NET_WM_WINDOW_TYPE_DIALOG", True);
+
+    XUnmapWindow(sd.display, lastGoodWindow);
+    XChangeProperty(sd.display, lastGoodWindow, _nwt, XA_ATOM, 32, PropModeReplace, (uchar*)&_nwd, 1);
     XSetTransientForHint(sd.display, lastGoodWindow, (Window)winId);
+    XMapWindow(sd.display, lastGoodWindow);
     XFlush(sd.display);
     return true;
 #endif