Re: [ft-devel] [GSoC] Extending the CF2 interpreter

[Werner LEMBERG]

> In the case of CFF, we get these values from `hhea' or `OS/2'. This
> includes a "line gap" value. But for Type 1, we can only obtain the
> ascender/descender values and not the line gap, as there is no such
> field in AFM.  I did even try editing the AFM file by hand in an
> attempt to get the lines to match up (in ftview's waterfall view),
> to no avail.

Indeed, font editors provide an educated guess for the line gap value
if converting from Type 1 to, say, CFF.

> So, regardless of the converter, we cannot obtain the same line
> spacing between Type 1 and CFF versions of the same font. In fact, I
> think most typesetting applications override line spacing anyway, so
> the importance of keeping this consistent is questionable. A
> reasonable compromise, then, is to just keep the current behaviour
> which is to use the bbox values.

Yes.

> In any case, the hinting seems to be consistent between the two, so I
> think the new interpreter is working fine.

Congrats :-)

> The metrics issues are from the module loading the glyph and may be
> bugs that need to be fixed later on.  Note that it only happens with
> fonts converted from CFF to Type 1, not between Type 1 old and Type
> 1 new, so this is a separate issue that exists on master branch as
> well.  For now, I'll move on to adding CID support and cleaning up
> the other changes first.

Thanks!


    Werner