Halo drawing slows down rendering significantly

A profiling session shows halo shape creation out of text shape is a pretty big hitter, sucks around 1/6th of the whole rendering time (and this is with the eager clipping still around, that sucks another 1/6th of the time, but that should disappear once we make it optional).
Now, thinking about it, it's evident that stroking the text outline repeats the same job for most labels, because chars and fonts are the same (usually).
Caching the stroked shape on a character basis and then putting them togheter in a composite shape may improve performance quite a bit.

I'm just opening this to avoid forgetting, it's a direction I want to explore further.