JScrollPane jitter during trackpad scrolling on MacOS/Aqua

[Eirik Bakke]

Hi, macos-port-dev.

Here's another bug report for Swing on Aqua/MacOS. In recent Java versions (6-12 months, not sure), trackpad scrolling in any JScrollPane has become extremely jittery, as demonstrated in the following video:

https://vimeo.com/151843642

The source code for the example app used can be found here: https://gist.github.com/eirikbakke/09a090ab8052d38c8c87
Note that the "implements Scrollable" business is not necessary to trigger the bug, I just did it to set the getScrollableBlockIncrement to something higher than 1 so that you'd see the jitter clearly on a video.

This happens in any app that uses a JScrollPane, including the NetBeans IDE's code editor and other scrollable panels, as well as in trivial apps like the linked example. The bug occurs consistently, with or without external monitors attached, at any resolution, and with or without simulated retina mode enabled. I'm on a 13-inch mid-2012 MacBook Air.

If no one knows about an existing bug report about this, I'll submit it on http://bugreport.java.com<http://bugreport.java.com/> (I searched bugs.openjdk.java.net ).

-- Eirik