I cannot reproduce the original problem, mostly because scrolling through combo boxes with the mouse wheel works just fine here even if the combo box itself is not focussed. Maybe this was different in Windows XP, or with some specific mouse drivers.

Anyway, the behaviour of this dropdown was also far from optimal when using keyboard navigation, so it has been tweaked in r18921, which should also help with the mouse wheel.

Sorry to reopen.
I am now on W7 64-bit fast computer with USB wired mouse, checking on OpenMPT 1.30.03.

Hhah! Bug still there after 12 years! �
Im sure your fix handled the issue and i look forward to testing it on the next stable.

Your original problem might be related to this recent forum post: https://forum.openmpt.org/index.php?topic=6945.0 - there seems to be some differences in Windows configurations (up to Windows 7?) where scrolling a dropdown list requires keyboard focus on some systems (where the bug could be observed) while it doesn't on some others (where the bug does not manifest). Do you use the Windows "classic" theme in Windows 7, or Aero with transparency effects? I think changing from to the other might fix that part of the issue. But either way, no matter how Windows is set up, the focus will no longer be diverted to the pattern editor when just scrolling through the list in OpenMPT 1.31, so the problem should be effectively gone.

Welcome back by the way!

I switched from Aero to Classic, started up MPT, and the behavior wasnt different.

It's still a mystery to me under which conditions it happens then. Not much we can do here, but the actual improvements in OpenMPT 1.31 should still make this feature more usable anyway.