Mouse scroll zoom while hovering pen

[cromachina]

I draw with my left hand and use my mouse with my right hand, so I end up frequently using the mouse scroll wheel while hovering my pen over my tablet to zoom at a point in other paint programs.

In Drawpile, if your pen is hovering, then the mouse partially locked out; That is, scrolling stops working (but some clicking still works). Only when the pen is lifted away is scrolling allowed again.

It would be nice if mouse scrolling can be enabled while the pen is hovering. Krita has the same issue, and I suspect it might be an odd Qt configuration thing. Comparatively both Clip Studio Paint and Paint Tool SAI allow you to hover your pen and scroll your mouse at the same time.

[askmeaboutlo0m]

Which operating system(s) does this happen on for you? I can sort of reproduce this on Linux on X11, where I can scroll with the mouse only if the pen is held still. But it also happens in e.g. any Chromium-based application, so not sure if it's something in Qt or even further up the stack.

[cromachina]

Linux (NixOS) X11.

I suspect Qt's event handling, because I can get it to work with CSP and SAI (also in Linux).

[cromachina]

Huh, I tried it in a Windows VM and it actually lets you do the scrolling and hover together. Maybe it's a bit of everything, Qt on Linux, X11, etc. together.

[cromachina]

Kinda works fine on Wayland, but KDE Plasma's Wayland also treats the mouse and tablet cursors as sort of weird separate entities.

[askmeaboutlo0m]

I'd suspect it's something in Qt's XCB platform abstraction then. I don't see any obvious point where it happens, but I would guess there's some sort of "current" input device somewhere that causes events from other input devices thrown on the floor.

And yeah, Wayland does the multi-cursor thing by default on Gnome and KDE. Sway-based window managers behave normally as far as I know. There's a bunch of other broken-by-design behavior in Wayland though, so I wouldn't recommend it as an alternative.

[cromachina]

I was able to make this happen with a minimal Qt program and filed a bug with Qt: https://bugreports.qt.io/browse/QTBUG-141252