See the KFMon announcement for a few possible caveats in the beta releases.
Basically, I'm throwing this in the wild and asking people to try and break it, to see if I squished all the bugs

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It's currently somewhat verbose, because I suck at basic maths & geometry

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EDIT: Also, no multibyte support right now. I'm vaguely looking into it, but the locales look fairly broken on Kobo, so that's going to be tricky at best...
EDIT²: "fairly broken" was an understatement. Please fix your damn libc, Kobo.
EDIT³: Worked around that shitstorm in 0.9.5. No validation of any kind possible, but we now "speak" UTF-8.