On Linux:
- drop a Button
- exit the tool
- The popup window appears : click Cancel
==> the tool exit, and the following error appears on stderr :


The program 'java' received an X Window System error.
This probably reflects a bug in the program.
The error was 'GLXBadDrawable'.
  (Details: serial 415 error_code 146 request_code 135 minor_code 5)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
Java Result: 1