[Bf-committers] Fake User for Brushes

[Jason Wilkins]

Brushes all have an extra reference count that keeps them from getting
deleted even when there is no paint mode that references one of them.  So it
is possible to unlink a brush from every paint mode and it will still be
saved in the .blend.  This apparently isn't a problem and is the purpose of
the fake user, however there is no interface that will allow a user to
permanently delete this brush or relink it into a paint mode again.  The
result is that if a user creates and deletes lots of brushes they will cruft
up the his saved files needlessly.  When I was editing startup.blend I
created/deleted several brushes while creating a new set.  I noticed this
problem and used the debugger to skip saving any brushes that were not in
use by any of the paint modes.

I'm assuming that the fake user acts as some sort of recycle bin so that
deleted objects can be retrieved so I think the main problem here is the
inability to recover brushes that have been unlinked.  In fact, there is no
way to even, for example, link a brush used in texture paint into vertex
paint or something like that.  (I may be wrong, before I changed it, the
same Draw brush was linked into 3 different paint modes, but as far as I can
tell I do not know how that was done).