Proper GUI scaling on HiDPI displays.

[johann-petrak]

Tested on a laptop with Ubuntu 20.04.1, 2880x1620 resolution set to 200% scaling in the default window manager. Tested with both the "fractional scaling" option enabled and disabled.

Tested to run a freshly installed revision 9532ab9 and also
on a freshly compiles (with Java 8) revision 81d16d5

Tested with Java versions:

• Java.net 11.0.8-open
• Java.net 8.0.265-open
• AdoptOpenJDK 15.0.1.j9-adpt

All three showed the splash screen and GUI without scaling.

Workarounds that worked for me in these cases:

• running with the parameter added: -Dsun.java2d.uiScale=2.0
• setting the environment variable GDK_SCALE=2.0 before running

Same with the Mate window manager

[johann-petrak]

Note to self: the following settings are mentioned on the internets for adjusting scaling or dealing with HiDPI problems:

• -Dsun.java2d.uiScale.enabled=false/true
• -Dsun.java2d.win.uiScaleX=2.0
• -Dsun.java2d.uiScale=1.0
• -Dsun.java2d.uiScale.enabled=false/true

[dianamaynard]

MacBook Pro (16-inch, 2019)
1280x720 resolution

GATE 9.0-SNAPSHOT build 81d16d5 started at Sat Jan 23 17:17:33 GMT 2021
and using Java 1.8.0_181 Oracle Corporation on Mac OS X x86_64 10.15.7.

Everything looks normal

[greenwoodma]

Dell XPS-13 with Ubuntu 16.04

3200x1800 display with the scale for menu and titlebars set to 2

Under Java 8 this results in a tiny little version of GATE that's half the size it should be.
Under Java 9 and above (at least up to and including 13) it works as expected with properly scaled fonts etc.

[johann-petrak]

@greenwoodma do the workarounds also work for you when the GATE is tiny under Java 8?

• running with the parameter added: -Dsun.java2d.uiScale=2.0
• setting the environment variable GDK_SCALE=2.0 before running

[greenwoodma]

No. If I use either on their own and Java 8 then it's still tiny, even using both at the same time makes no difference.

[johann-petrak]

OK so it seems behaviour depends on both the Java and Ubuntu versions.

[greenwoodma]

Yes, it looks like you have different display options (i.e. fractional scaling) which I don't in 16.04 so my guess is this affects the numbers that Java retrieves from the OS and hence how it then scales things; one of the numbers used deep in the scaling comes from the AWT Toolkit under the property name "gnome.Xft/DPI"