Re: [ft-devel] Problem with Postscript Hint

[PILLET Céline]

Hi John,

 

Thanks a lot for your answer.

I find the random generator, but it can’t explain what I’m experiencing.

 

Celine.

 

De : address@hidden [mailto:address@hidden De la part de John Tytgat
Envoyé : mardi 3 mai 2011 12:35
À : address@hidden
Objet : Re: [ft-devel] Problem with Postscript Hint

 

On 5/3/2011 9:52 AM, PILLET Céline wrote:

I have a problem with hints of PostScript fonts.

I create 2 consecutives bitmap with a postscript font, with a multithread program, and rendering differs slightly.

I don’t have this problem when I create bitmap without “hints”.

I don’t have this problem when I create bitmap with “hints”, in a single thread program.

Do you have an idea of ​​something that is not thread safe in the PostScript hints code?

 

If you mean 'PostScript font' = Type 1, CID or CFF font', search for 'seed' used for implementing a random generator.  This is calculated based on location of stack variable.  This *could* explain what you're experiencing but I'm not sure.

Question for the FT developers : why was this seed calculation implemented this way ? And not e.g. a fixed start value associated with each FT_Face created ? That would make FT output reproducable (and testable for detecting regressions).

John.