When trackpad swipes don't convert to ScrollWheel steps anymore, several hardcoded
wheel events need to support swipe too.
This adds swipe support to:
- Menu item scroll
- Search item scroll
- ALT + number/slider/swatch values
The amount of old style scroll "clicks" is calculated based on how trackad is
being mapped to move a mouse pointer. Move it one widget unit = 1 click.
The swatch option applies trackpad swipe motion in analog way.
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