Scrolling the mouse wheel to zoom sometimes gets stuck going in only one directly

[trampster]

Mapsui Version
4.1.2

Mapsui Platform
Avalonia, I haven't tested on any other platforms

Device
Linux (Ubuntu 20.04)

Describe the bug
When scrolling to zoom sometimes it gets stuck going in only one direction, for example both scrolling up and down with zoom out, or both scrolling up and down will zoom in.

It will also come right after a while of trying, with no obvious thing that you have done to fix it.

To Reproduce
Steps to reproduce the behavior:

1. Launch an Avalonia app with a mapsui map (can be reproduced with the samples app)
2. Scroll in and out until it starts going wrong (it can take a while to happen and it's not obvious what triggers it)

Expected behavior
Scrolling up always scrolls up and scrolling down always scrolls down

[pauldendulk]

The word scrolling in a general context means going up or down, which would be a form of panning in Mapsui. But I assume that here you are talking about mouse wheel scrolling which would be zooming in and out in Mapsui (although because of the mouse position there is also some displacement of the map). Is that correct?

[trampster]

Yes using the mouse wheel to zoom.

[pauldendulk]

Mouse wheel zoom on Avalonia needs a workaround because the default step size (of a factor of 2) was too big because there are more touch event. This workaround may have introduced a bug. I am working on mouse wheel zoom to allow smaller step sizes so we could remove the workaround.

[pauldendulk]

I can not reproduce this on Windows.

In 4.1.4 there will be an option to use an alternative mouse wheel method. You could try if that fixes the problem. Use: MapControl.UseContinuousMouseWheelZoom = true;