RE: [ft-devel] FreeType 2.3.5 - incorrect bitmap_left / horiBearingX values with Symbol TT font

[Bevan, David]

Werner,

 

Is there any harm in making the following change in TT_Load_Glyph()

 

     Replace

 

        if ( ( face->header.Flags & 2 ) == 0 && loader.pp1.x )

          FT_Outline_Translate( &glyph->outline, -loader.pp1.x, 0 );

 

     with

 

        if ( loader.pp1.x )

          FT_Outline_Translate( &glyph->outline, -loader.pp1.x, 0 );

 

in order to accommodate bad fonts like this?

 

Or does this have some unwanted side-effect?

 

David %^>

 

 

 

> -----Original Message-----

> From: Werner LEMBERG [mailto:address@hidden

> Sent: 23 February 2008 07:40

> To: Bevan, David

> Cc: address@hidden; Brazier, Stephen; Ghoshal, Ronen; Nagpal,

> Shipra

> Subject: Re: [ft-devel] FreeType 2.3.5 - incorrect bitmap_left /

> horiBearingX values with Symbol TT font

>

> > We've just upgraded from FreeType 2.1.9 to 2.3.5 and encountered a

> > regression issue.

> >

> > With the attached Symbol TT font, the "left side-bearing" values are

> > incorrect for some of the characters.

> >

> > For many characters, both the bitmap_left and horiBearingX values

> > are now zero. Some others are incorrectly too large.

> >

> > The first character to show the problem is glyph 3, the '!'

> > character.

> >

> > For this character (16pt at 300dpi), with 2.1.9, horiBearingX was

> > 448.  With 2.3.5 it is now incorrectly zero. Similarly, bitmap_left

> > was 7 and is now also zero.

>

> This isn't a bug in FreeType 2.3.5 but a bug in the font itself.

>

> To cite the OpenType specification, documenting the `glyf' table:

>

>   The scaler will perform better if the glyph coordinates have been

>   created such that the xMin is equal to the lsb.  For example, if the

>   lsb is 123, then xMin for the glyph should be 123. If the lsb is -12

>   then the xMin should be -12.  If the lsb is 0 then xMin is 0.  If

>   all glyphs are done like this, set bit 1 of flags field in the

>   'head' table.

>

> However, in your Symbol.ttf (which is version 1.00), this bit in the

> `head' table is incorrectly set to 1, indicating that the left side

> bearing values in the `hmtx' table can be ignored because those

> offsets are already applied to the coordinates in the `glyf' table.

>

> Later versions of Symbol.ttf (e.g. version 1.60 which I have) have

> this bit cleared, and FreeType 2.3.5 correctly honours it (while 2.1.9

> doesn't).

>

>

>     Werner