[ft-devel] proposed patch for diagnostics (Re: implementing detection of hinting/rasterization errors in fonts)

[Hin-Tak Leung]

Hi Werner,

Here is likely the final form of mod to freetype that I am putting in as part 
of the next release of font validator. Mostly it is just two new APIs : to set 
and unset an external diagnostics messaging routine, and a macro which wrap 
around it to call it in a nicer way: DIAGNOSTICS("message", where).

The rest is just a lot of scattered:
     "DIAGNOSTICS('message", where)",
or 
     "if (simple_condition)  DIAGNOSTICS('message", where)".

If you re-define the macro to nothing, it causes no functionality change to 
freetype at all.

The end result is simplier than I thought, as mostly freetype already detects 
and silently works around the errors; so it is mostly about finding out or 
deciding *where* to put the DIANOSTICS().

Sorry that the "message" part is a string - it turns out to be more convenient 
for me to have it as a string on the freetype side, instead of having it as a 
enum. The set of such strings - I only use 6, but eventually there will be 70+ 
of them - are a subset of the ~800 enums
(those that starts with "_rast_") in

https://github.com/HinTak/Font-Validator/blob/master/OTFontFileVal/atoms.cs

Trimming (i.e. removing the "_rast_" part) or name-space prepending 
("FontVal_rast_") don't add any trouble to me. So if that's more preferable?

Hin-Tak

freetype.diff
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