[Devel] FreeType Cache in multithread program

[Jan Slupski]

Freetype developers,

Hi! 
I would ask the question - I couldn't find it anywhere clearly 
explained in the docs.

How FreeType Cache (and FreeType itself) works in multithread environment?

Is it all right to have only one Cache structure created for use by
multiple threads, or it's necessary to have one cache per thread?

My question is because I'm getting occasional bugs when rendering fonts
with FT 2.1.3 (with caching).

It looks like the font (face) is sometimes exchanged with other.
Sometimes only some glyphs are wrong.

I cannot exclude that this is bug on my side, but I would like know
your opinion on multithread safety of FreeType...
Bug disappears when creating one cache per thread.

Currently it's rather hard to track this down, because it happens
a few times per hundreds of runs (performed eg. in 50 concurrent threads).

I would add more debug information, but I haven't idea what can help
clearing/understanding the situation.

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