HighDPI Scaling Bug On Linux With JavaFX Interoperability With SWT (Possible Solution)

[marcel Austenfeld]

I filed this bug regarding the high dpi scaling on Linux when using the FXCanvas for SWT:
 
https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8233181
 
I think I found the problem in the FXCancas class whereas the Linux case is simply not handled:
 
https://github.com/openjdk/jfx/blob/master/modules/javafx.swt/src/main/java/javafx/embed/swt/FXCanvas.java#L174

https://github.com/openjdk/jfx/blob/master/modules/javafx.swt/src/main/java/javafx/embed/swt/FXCanvas.java#L240
 
In both cases the scale factor for MacOSX and Windows is returned (by reflection) but not for Linux which I think i the same method as for Windows.
 
Thus the scaling factor is always 1 which leads to this graphical distortion (if I set the scale with DPIUtil.setScale differently I can also cause a distortion!)
 
However I was not able to built openjfx on Ubuntu 19.10 so far.
 
Is there a gradle command to built the swt module only?
 
@Kevin Rushforth: can you confirm that this is the cause for the bug?
 
Unfortunately there is no issue tab on the Github page so I post here.