Manual falloff adjustment does not
use the preview rectangle
Versions affected
4.0
Description
When an overlap region is open, moving the slider to manually adjust
brightness falloff should redisplay only within the preview rectangle,
It should redisplay the entire image only when you release the slider.
Instead, it redisplays the entire image as you move the slider.
This causes the screen updates to be very slow and interferes with the
interactive adjustment of brightness falloff.