When using the mouse wheel in strictly one direction, it is possible to move a Slider in BOTH directions!
When moving slowly or quickly, the slider moves in the expected direction. But with the right speed somewhere in between, the slider moves in the opposite direction.
I tried to figure this out by myself, but strangely Slider::Pimpl::mouseWheelMove was never hit in XCode 5. I outcommented
if (e.eventTime != lastMouseWheelTime)
as well as
(wheel.isReversed ? -1.0f : 1.0f)
but neighter changed the situation.
This happens in my own application as well as in the JUCE demo and even in Tracktion.
I tried it with a Logitech mouse as well as with the Trackpad of my Macbook under OSX 10.9.4.