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Re: [ft-devel] GSoC status update.


From: Werner LEMBERG
Subject: Re: [ft-devel] GSoC status update.
Date: Tue, 17 Jul 2018 18:55:10 +0200 (CEST)

>> I wonder whether it makes sense to add an artificial space glyph to
>> the GF + TFM combo – most font formats have a space glyph for
>> simple string support...  What do you think?
>> 
>> The width of such a space glyph could be derived from TFM's
>> `param[2]' value.
> 
> I don't really know how to work that out.  Can you suggest any
> format which does this?

FreeType already does that for some formats: The glyph with index 0
must be the equivalent to the `.notdef' glyph (also known as the
`undefined glyph' or `default glyph') – cf. the WINFNT or BDF driver.
BTW, it seems this feature is still missing in the GF driver, so
please add it.  The actual shape of the glyph with index zero doesn't
matter; for example, you could construct it on the fly (i.e., while
loading the GF file), say, a bitmap that contains a hollow box as with
most TrueType fonts, scaled to the proper font size.

   XXXXX
   X   X
   X   X
   X   X
   XXXXX

Similarly to the above you should construct a second artificial
character to hold the space glyph (i.e., an empty bitmap which only
has an advance width); for convenience, I suggest this glyph gets
index 1.  As a consequence, you would have to shift all (native) glyph
indices by two; a GF font with 128 glyphs becomes a font with 130
glyphs, etc., etc.

In case no TFM file is attached to the GF file, please use the font
size to derive a heuristic width for both the `.notdef' and the
`space' glyphs.


    Werner


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