Steps to reproduce: 1. On Mac, open a Firefox window with WebRender enabled and open enough tabs to cause the tab bar to scroll. 2. Move the mouse over the tab bar. 3. Scroll horizontally using your touch pad. Scrolling gets stuck and results in back/forward navigations. The tab bar has a wheel handler; it seems we're not treating the tab bar as a dispatch-to-content region the way we should.

This is an annoying issue when dogfooding on Mac

I guess I don't really run into this because I use TreeStyleTab. I'm working on hooking up WR hit-testing and hope to have that in place in a few days. The first cut will still have some problems but it might fix this bug; if not I can look into this after I'm done that work.

Markus, do you see this with "gfx.webrender.hit-test" enabled?

I don't see this with "gfx.webrender.hit-test" enabled.

Fixed by bug 1421380 which makes gfx.webrender.hit-test on by default.

Hi, I can't seem to reproduce this issue using only the steps here. I'm using a 2017 MacBook Pro with Touchbar and it has macOS High Sierra 10.13.4. I've installed and tested the issue on Nightly 60.0a1 (id: 20180305100134) and Beta 60.0b3 but had no luck on either of them. I used the STR from Comment #1. Markus, am I missing something here?

The bug is specific to WebRender, which is not enabled on Beta. If you want to repro the problem you'd have to try it on a Nightly build from before the fix landed, and with webrender turned on.

Hello, I have managed to reproduce the issue using kats' indications from comment #8 and Nightly 59.0a1 (id: 20180120220330) (thank you for that) and I can confirm that this issue is fixed in the Nightly builds after bug 1421380 was fixed. Tested on Nightly 61.0a1 (id: 20180328141001) on macOS 10.13.4