I'm uncertain as to the exact trigger for this incident, but it begins after one to five minutes of use. Whenever moving the mouse over a drop down menu, button, tab, or other object with an active mouseover event where the object highlights or changes (So also the Level/HP/Class table for Class & Level) the active window will begin duplicating within the confines of the pane.
It is not confined to one tab, and even occurs on the new/open/save buttons and the file menu. I have attached screenshots.
I attempted to find other issues with the words mouseover, tab, and button, as I was unable to think of another way to phrase the issue. I apologize if this is a duplicate issue.
Windows 10 Pro x64, 8GB DDR3, i5-2500K
Duplicated on Java 8u111, Java 8u101, Java 7u45, both running as JAR and through Windows executable.
I found a single StackOverflow thread with issues tied to Swing and the J2D_D3D variable. Running PCGen as a jar with '-Dsun.java2d.d3d=false' seems to correct the issue. So it appears to be unrelated to PCGen itself and instead is related to the 1.8 JDK.
I've been out of Java for a while and couldn't remember the name of "Swing" so my searches didn't turn this up until I broke out a textbook. It seems this can be resolved without issue.
Anyone having this issue in the future just needs to run the batch and disable the variable.
The issue is with the 1.8 JDK and not PCGen.
To fix, create a batch file to disable the J2D_D3D variable and run PCGen directly.
java -Dsun.java2d.d3d=false -jar pcgen.jar