does this break compatibility?

#97561 seems to be Reproducible again

#97561 seems to be Reproducible again

I tested again and found that #107302 did not fix #97561(sorry for that wrong comment). It seems to occur only when the step is 0. Pushed the change to resolve it.

bool use_custom_arrow_step should be removed as it is not being used anymore since #107302

One issue I noticed though is that if step is 0, then step will become custom_arrow_step, which breaks manual input. This is probably unintended.

This is effectively what #107302 aimed to fix, but this PR reverts it to fix another issue. We probably need to think of a better solution in the long run.

So from now on custom_arrow_step needs to be a multiple of step to function properly…
Maybe this should be documented

So from now on custom_arrow_step needs to be a multiple of step to function properly… Maybe this should be documented

Not exactly, it works the same as a multiple of step, but doesn't need to be a multiple of step.

That seems like a bug in #97573. This behavior was never intended 😅.
behavior should have remained the same as 4.3

I do see some spinbox does not round by arrow step by default (e.g. in KDE Plasma), but there seem to be some are.
Perhaps we can add a property to control whether the arrows round the value.

seems like a good idea. But it can probably wait till 4.6

Opened a separate PR #108335 for that.

Thanks!