Currently missing an important feature (X8 & X9) that used to work for the basic paintbrush and for special effect brushes (emboss, soften, lighten/darken, etc.):
continuous mode. Continuous mode works with the Opacity setting, preventing build up of color or effect when overlapping coverage.
The Continuous checkbox is still there, but... it does not appear to effect brush behavior.
And some brushes now work in continuous mode all the time, others do not.
This has been reported broken since X8.
Checking continuous does not seem to effect the Lighten/Darken brush at all, it keeps increasing the effect.
The basic paintbrush and the Emboss brush appear to behave in "continuous" mode regardless of whether this box is checked or not.
Continuous mode is a great feature, so I hope this comes back!
