SPHINCS visualization misbehaves

[simlei]

Plugin path: /org.jcryptool.visual.sphincsplus

A video tells it best:

During the capture of the video, I get a ton of exceptions thrown because of disposed controls, which usually is a very bad sign for visualization implementation when being thrown periodically -- there is something going on in the background.

org.eclipse.swt.SWTException: Graphic is disposed
    at org.eclipse.swt.SWT.error(SWT.java:4711)
    at org.eclipse.swt.SWT.error(SWT.java:4626)
    at org.eclipse.swt.SWT.error(SWT.java:4597)
    at org.eclipse.swt.graphics.Color.getRed(Color.java:303)
    at org.eclipse.swt.graphics.Color.equals(Color.java:233)
<snip>

https://pastebin.com/GMU0CjMp

I realized there is a background process that does not pay attention to resource lifecycle before -- this issue seems at least distantly related: #258

Following https://github.com/eclipse/gef/wiki/Zest-Examples and https://bugs.eclipse.org/bugs/show_bug.cgi?id=469126, I already tried to set SWT_GTK3 to 0 as follows:

But the video is recorded using that setting. I seemed to notice a difference after the change so I'm confident the environment variable was picked up.

Platform: Linux/GTK

[simlei]

Due to incompatibility of ZEST feature (graph embedded in graph) with GTK, the two rightmost tabs have been disabled under Linux.