Some external references:
JEP 283: Enable GTK 3 on Linux
[JavaFX] Conditional support for GTK 3 on Linux
[JavaFX] Backport GTK3 support on Linux to 8u

any opinion?

How do we test this?

what do you mean? as in nixos testing framework? No test are needed because default behavior is the same. We can start to disable gnome2 in app by app basis after this. Have sense?

I meant do you have an app I can test this with?

Wow, it's true that nobody is using openjdk11 in nixpkgs. I make a grep search and the only candidate is ghidra-bin, I'm testing it now. Also I'm building Bisq but is not yet finalized for commit.

I've test ghidra-bin without gnome2 but GUI doesnt work. I'm wondering: with only 2 leaf packages depending on openjdk11 maybe I could try to remove totally gnome2 deps while trying to make ghidra work?

Do you know if the JavaFX/Swing/whatever is toolkit independent? Is the API abstract enough that apps do not have to care about which version of GTK are we using? If so removing gnome2 deps altogether would be a good idea.

Sorry but i don't know. i'm not very familiar with Java stuff. Anyways I feel confident to research and test it.

Thank you for your contributions.

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Both gtk2/gtk3 is only a runtime dependency, not even a build dependency: https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/java-openjdk#n179
Therefor I think we could drop gtk2. It seems to be used for themes.

glib is required to read proxy settings from GSettings.

If java.net.useSystemProxies system property istrue, GSettings is checked (and GConf is checked if GSettings is not available).

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/doc-files/net-properties.html
https://github.com/openjdk/jdk11u/blob/master/src/java.base/unix/native/libnet/DefaultProxySelector.c
https://github.com/openjdk/jdk11u/blob/727ddb06fd780ecba80dd31db0700a0005ffedda/src/java.base/share/classes/sun/net/spi/DefaultProxySelector.java

The main motivation for this change was to workaround a crash in Bisq software. Nowadays Bisq is working nice with vanilla openjdk11 as in latest nixpkgs commit.

So I close this PR because have big implications and require in-depth java knowledge.