Support high-density screens

[mlopatkin]

Original report by me.

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On 4K displays (e.g. 15" 3840*2160) the app window is too small. It needs to support default platform scaling.

I've tested on Linux (Ubuntu 16.04.1) only, because I don't have Win/Mac device with 4K display yet.

[mlopatkin]

The workaround that I use now is to run the app with JDK 11. Support for HiDPI in Swing was added in JDK 10, now it respects system-wide scaling. However, Android developers often stuck on JDK 8 so some solution is needed here:

• add command-line key to scale manually?
• ship embedded JDK 11 with the app with javapackager or alike?

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[mlopatkin]

Another workaround (on Windows) is to use JDK bundled with Android Studio (aka JetBrains Runtime). One needs to point JAVA_HOME to the Studio's JDK and set LOGVIEW_OPTS=-Dsun.java2d.uiScale.enabled=true in environment.

[mlopatkin]

It looks like the Linux situation is more broken than I thought. I've failed to set up 1.5 scaling on Ubuntu 16.04 with JDK 11. The same configuration seems to works on my desktop though (I need to re-check). Setting 2x scaling with GDK_SCALE=2 or -Dsun.java2d.uiScale.enabled=true works though.

[mlopatkin]

Fractional scaling on linux seems to be affected by https://bugs.openjdk.java.net/browse/JDK-8214227 (i.e. not supported)

[mlopatkin]

Fractional scaling is not supported by Jetbrains Runtime as well: https://youtrack.jetbrains.com/issue/JBR-1365

Not so many options left:

1. Manual scaling everywhere (moderately difficult)
2. Check if JavaFX supports fractional scaling and rewrite UI in JavaFX (checking is easy, rewriting is hard however beneficial to code health and my knowledge of JavaFX :))
3. Check if SWT supports fractional scaling and rewrite UI in SWT (again, checking is easy, rewriting is hard and I'm not sure SWT is a feasible choice).

[mlopatkin]

JPackage is going to hit stable in Java 16. I should probably bundle the runtime with the app so users with HiDPI displays don't have to set up a separate JDK.

[mlopatkin]

The simplest option might be to use flatlaf, it supports HiDPI. There are problems with colors though - default selection color doesn't play well with my priority colors.

[mlopatkin]

Still works weirdly in my Linux environment and JDK 11 (Unity, scale 125%). The scaling is way to large, 200% or even more.

[mlopatkin]

Still works weirdly in my Linux environment and JDK 11 (Unity, scale 125%). The scaling is way to large, 200% or even more.

Playing with flatlaf demo, I can see that it is indeed 200%, but only on JDKs 11-16. JDK 17 works fine. And I suppose, it might be different in Gnome/KDE. AARGH!

[mlopatkin]

I give up. My other Linux box doesn't reproduce the problem, FlatLaf picks up user scale (1.25) successfully. I'm closing the issue, one can use -Dsun.java2d.uiScale.enabled=false to force user scale, I guess.