Re: [Devel] cmap4 validation test problems

[David Turner]

Hi Werner,

Werner LEMBERG wrote:
> David, please note that the validation tests for cmap format 4 (in
> ttcmap0.c) are too strict for many CJK fonts.  Most notably, these
> two tests often fail:
>
>     ...
>
>     ends      = table   + 14;
>     starts    = table   + 16 + num_segs * 2;
>     deltas    = starts  + num_segs * 2;
>     offsets   = deltas  + num_segs * 2;
>     glyph_ids = offsets + num_segs * 2;
>
>     if ( glyph_ids >= table + length )
>       FT_INVALID_TOO_SHORT;                             <<<<<<
Hmmm.. it seems this test is too strict. It should
read:

      if ( glyph_ids > table + length )
        FT_INVALID_TOO_SHORT;

instead.


>      ...
>
>      for ( n = 0; n < num_segs; n++ )
>       {
>         p = starts + n * 2;
>         start = TT_PEEK_USHORT( p );
>         p = ends + n * 2;
>         end = TT_PEEK_USHORT( p );
>         p = deltas + n * 2;
>         delta = TT_PEEK_SHORT( p );
>         p = offsets + n * 2;
>         offset = TT_PEEK_USHORT( p );
>
>         if ( start > end )
>           FT_INVALID_DATA;
>
>         if ( n > 0 && start <= last )
>           FT_INVALID_DATA;                              <<<<<<
Hummm.. if "start <= last", then the ranges defined in
the charmap are simply overlapping, which seems to be
quite an important bug within the font..

I'll try to have a look at the Chinse Arphic fonts
and see how their charmaps are organized..

I'll commit all changes to the CVS soon..

Thanks,

- David Turner
- The FreeType Project (www.freetype.org)