Unable to middle click while moving when Button Scrolling is active
I'm using libinput on a Thinkpad W530 with trackpoint. I enjoy Button Scrolling on the middle mouse button, but also frequently use the middle mouse button for regular clicks.
Recently, this has become harder. Middle clicks are frequently being ignored when the cursor is still moving (slowly) by the time the button is pressed. It instead instantly jumps in Button scrolling mode. It seems something was changed to allow Button Scrolling to start without having to stop the cursor first. Unfortunately this does not agree with my muscle memory at all and causes frustration, e.g. when trying to quickly open many links in the background in browsers.
I am seeing the bug in libinput 1.13.1, but it's hard to pinpoint when exactly it started. I suspect it was 1.13.0 or 1.13.1.
I think the issue is simple and reproducible enough to not require recordings, but will be happy to attach them if requested.