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From Simon Pepping <spepp...@leverkruid.eu>
Subject Re: Implementing OpenType font support, how hard?
Date Thu, 03 Aug 2006 13:04:40 GMT
On Wed, Aug 02, 2006 at 06:44:28PM +0200, Vincent Hennebert wrote:
> >> 3) Additional steps for OpenType GSUB table support
> >> The goal is to enable the "smart font" features of OpenType, automatic
> >> ligatures as mentioned above, language-dependent glyph substitutions
> >> (different shapes if a letter is at the beginning of a word for
> >> example), automatic decorative swashes at the beginning or end of
> >> words, etc.
> >>
> >> 3b) Modify the chars-to-metrics mapping to handle things like
> >> automatic ligatures, where several chars map to a single glyph
> >
> >Here I think you can profit from my work on kerning to handle special
> >cases.
> The only problem I see with ligatures is when a word may be hyphenated
> between two characters for which there is a ligature: if it ends up
> being hyphenated the separate glyphs should be used, otherwise the
> ligature glyph should be used. I don't think this can be easily
> represented in the current Knuth glue/box/penalty model which is used to
> break lines into paragraphs.

I think it can be done, and is similar to things that have been done
in FOP.

The main problem with all these smart font features is that you cannot
implement them in rendering without also implementing them in the
linebreaking code. The linebreaking code must be able to correctly
predict the metrics of the characters that are going to be rendered.

> >> 3d) Create test documents to demonstrate this, asking a font provider
> >> for a donation of some OpenType fonts to use in FOP tests.
> >
> >That's one possibility. Another one might be the DejaVu fonts which we
> >have found after a LOT of searching for a font with an ASF-compatible
> >license. However, I haven't received any official feedback on license
> >compatibility, yet. OTOH, I'm not sure if those fonts will enable you to
> >show off all the features you want to implement.
> Aren't DejaVu fonts only TrueType fonts?

Have a look at the STIX fonts,
http://www.stixfonts.org/swdev_geninfo.html. I believe they will
distribute OpenType fonts with Type1 outlines. Their pace of
development is quite slow, but now they are nearing completion of the

Regards, Simon

Simon Pepping
home page: http://www.leverkruid.eu

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