[HarfBuzz] towards an OT debugger

[Martin Hosken]

Dear Behdad,

Thanks for your help in getting the debug output from hb. I've been playing and have some thoughts about how to use the existing debug framework to help with font development.

1. It would be great if the HB_DEBUG variable controlled which categories of debug are output, rather than the depth. For example, I don't need the SANITIZE debug (and pretty much anything else than APPLY).

2. It would be good if we can get the lookup index, somehow, into the debug report. I don't think it's stored in the lookup. But I may be wrong.

3. Is there a way to print out the whole buffer as per, perhaps, the output from hb-shape. And can we call that from when a lookup starts.

These would be the basics. I'm sort of thinking about creeping up on the problem rather than building some massive implementation layer either to the side or inside. If we can get the debug system to print at least the info we need, we can have it call a side library to do the debug reporting later on.

TIA,
Yours,
Martin