I had to dig in intellij community source code, as horizontal scrolling works fine there and it also happens to use Java AWT.

I attached jdb debugger to intellij and put a breakpoint on "MouseWheelEvent", simulated horizontal scroll, and it lead me to the code snippets below :

Here's how it's handled in intellij

https://github.com/JetBrains/intellij-community/blob/654dcd7a253d7f527b1d4d6d17be532a40775b1d/platform/platform-impl/src/com/intellij/ide/IdeEventQueue.kt#L1032-L1049

https://github.com/JetBrains/intellij-community/blob/654dcd7a253d7f527b1d4d6d17be532a40775b1d/platform/util/ui/src/com/intellij/util/ui/StartupUiUtil.kt#L184-L189

I copied these three methods in this commit to a custom JadxEventQueue, should I mention the original sources in the code ?

Anyway, horizontal scrolling is now working as expected

• Closes [gui] Unable to use horizontal scroll wheel to scroll the code area #1988
• Fixes BUG: jadx-gui: invalid mapping for horizontal scroll wheel and forward mouse button #1718, and fixes [GUI][bug?] Fix horizontal scrolling on touchpad #1960, as horizontal scrolling still doesn't work