Re: [ft] FT_Glyph_Get_CBox inaccuracy

[Werner LEMBERG]

> I'm having some trouble computing the bounding box of glyphs.  It's
> possible that I haven't understood the purpose of the
> FT_Glyph_Get_CBox function.  In my understanding by using this
> function I should get the extreme coordinates of the glyphs,

Yes, if you ask for font units.

> and these coordinates should match exactly the extreme coordinates
> of the rendered glyphs.

No.

> For example, if I render all the glyphs of Arial version 5.06 using
> the default character map (the character map selected by FT) with
> 72px size, from 2814 glyphs i get inaccurate bounding boxes for 186.

This has been recently discussed on the mailing list; see for example

  http://lists.gnu.org/archive/html/freetype/2010-02/msg00065.html

which also shows an image of a debugging session with Arial.
Hopefully, this clarifies the issue.

> If it's a bug I would be happy to help fixing it,

It's not a bug.  However, I would be glad if you could suggest an
improved wording of the documentation (w.r.t. the version in the git
repository).

> if it's not please give me some advice how can I get accurate
> bounding boxes without actually rendering the glyphs.

This is not possible.


    Werner