Upgrade to Java 11

[ennerf]

Benefits

• Smaller binary size due to modularization in Java9. Should reduce binary size from ~80MB to somewhere between 15-25MB
• Various bugfixes in JavaFX. I don't think there is anything major though that is currently an issue for us. (The Linux native memory leak seems to only depend on the Mesa3D library)
• Java 11 moved JavaFX into a separate project that isn't bundled with the JDK, which will likely speed up the development cycle.

In order to upgrade, we are mainly waiting for our whole build chain to support the Java9 modularization

• IntelliJ: some issues, but supported well enough
• Maven: some issues, but supported well enough
• ProGuard: Fixed Aug 2018
• ProGuard Maven plugin: soon?
• Javapackager Maven plugin: TBD

Development links:

• JavaFX on JDK11
• Maven multirelease jars
• Building MR JARs with Maven
• Automatic Module Names
• Java9 Modules Cheat Sheet

[ennerf]

Once we upgrade, we can also remove the tooltip hack required for https://stackoverflow.com/a/43291239/3574093

[ennerf]

It looks like the ProGuard Maven Plugin now has a workaround.

The Javapackager was completely removed from JDK 12, so it'd have to be built with a previous version (e.g. JDK 10 packager executable). With that in mind, it may make sense to remove the maven plugin and to separate out this step so we can finally update.

[ennerf]

JavaFX 12+ has a new maven plugin and can be used like a library

Getting Started
Maven plugin for javaFX 11+