Eclipse RCP HighDPI Scaling on Linux broken with embedded JavaFX

[marcel Austenfeld]

I already filed a bug report (with screenshot) to the Eclipse bug database but I think JavaFX is responsible for this weired behaviour on Linux and GTK 3, see:
 
https://bugs.eclipse.org/bugs/show_bug.cgi?id=546011
 
The bug only occurs when the display settings (e.g., on Ubuntu - but also tested on Debian and Arch KDE) is set to a scaled mode of 2 which is the default setting on high dpi displays.
 
I tested this mainly with a screen resolution of 3000*2000 but also with VirtualBox on a Retina Display.
 
At 100% (scale 1) the application works fine and the bug does not occur.
 
As described in the bug report if I open at startup only SWT view perspectives everything scales correctly at scale factor 2.
 
However if I then open an embedded FXCanvas (e.g. an integrated SceneBuilder perspective) the whole application is scaled to 1 and
all parts are not repainted correctly (see screenshot Eclipse bug database).
 
I run my application on OpenJDK 12 with OpenJFX 12.
 
An older version  of my app based on Java 1.8.72 and the embedded JavaFx (GTK 2) works fine and does not show this behaviour on HighDPI.
 
Are there any new settings which could cause this behaviour on GTK3?