Re: [ft-devel] GF + TFM

[Werner LEMBERG]

>> Please have a look how AFM files are attached to Type 1 fonts; it
>> basically does the same, namely to add more metric information.  I
>> suggest that you use this as a template.
> 
> If we use this as a template, then there is no need to have a
> separate TFM driver, as VFlib's TFM driver only provides functions
> to extract the TFM metric data for the `vf' format, which we can
> constitute like in the `afm' files.

A separate TFM module makes sense IMHO, since exactly the same code
will be used for the PK module also.  And VF will need this, too.
Compare this to the `psaux' module which provides routines for CFF,
Type1, Type42, and CID fonts.

The AFM code handling is restricted to Type1 fonts; it thus doesn't
make sense to have a separate module.

> Although, this driver computes some glyph metric data using this tfm
> data, which essentially draws some glyph only having bounding box.
> I am confused like if we proceed with the `afm' style should there
> be TFM driver or not?

Well, the TFM driver will be a *passive* module, similar to the AFM
handling code.  This means that it won't be called in the loop that
tries to find out an input font's file format; instead, it becomes
only active if a TFM gets attached to a GF or PK file.

The job of the TFM module is to parse a TFM file and to fill metrics
and/or kerning structures (cf. `T1_Read_Metrics', lines 266-282).  If
everything's OK, it will overwrite and/or add data to `GF_Face' or
`PK_Face' (cf. `T1_Read_Metrics', lines 296-316).

Does this help?  And sorry if the phrase `using as a template' was
misleading.


    Werner