Comment 6 for bug 170588

The bug you merged with,
https://sourceforge.net/tracker/?func=detail&atid=604309&aid=1275286&group_id=93438
contains lots of information.

Using rasterization is a bad bad bad idea. DONT.

Instead do whats proposed in the bug above - use set operations.
Just cut the active layers (you can make white lines
inactive if you want to) with a big box, then delete every
generated chunk of the big box except the one the user would
have clicked upon. This gives you a nice path object.