I really wanted to get this one in because 'how do I snap the mirror line back to the center' is a very common question. Furthermore, when doing game art, being able to snap the mirror line to the grids would be really useful.
The barebones are there. The snapToGuide function is adapted from KisTool.cc, the events get read properly etc... The onlyweird thing is that when doing snapGuide->snap(blahblah), the point that gets sent in doesn't get snapped to anything. And qdebugging doesn't tell me what is going on.
I figured this would be better than email. (BTW, test out the mirror guide beforehand, there's a strange twitching going on when using a tablet, and I am 100% sure that isn't my patch's fault).