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From: | Parth Wazurkar |
Subject: | Re: [ft-devel] GF + TFM |
Date: | Wed, 25 Jul 2018 13:35:45 +0530 |
>> 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?
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