Re: [Devel] freetype layout -- Where?

[Tobias Hunger]

On Mon, Aug 27, 2001 at 11:30:15AM +0200, David Turner wrote:
> Don't expect any real code before _lots_ of months :-)

I strated a library, but that's just to toy around with some ideas and
to get a feeling for the APIs involved and the data stored in opentype
fonts. So don't exspect any code from this:-) But it should help me get
into FTlayout if that's what we will need.

>   - heavily Unicode-biased.
>
>   - only supports UCS4 (i.e. 32-bit Unicode charcodes) [...]

I fully agree with these two points.
 
>   - provides "styles" [...]
> 
>     (For a better idea, have a look at ATSUI, i.e. Apple Text
>      Layout Engine)

Any URLs about ATSUI?

I don't think we will need styles at this level of our API-stack:-) 

>   - we'll most probably start using UCI as the back-end for
>     most layout operations [...]

URL for UCI? (or do you mean ICU?). Will you write FTlayout in C++? That
way you propably won't need most of your support library;-)

We won't need the unicode layout functionality (at least not the
bidir-part), we just need a way to get to the font-data (GSUB, GPOS and
maybe some other tables iirc) and use that.

>   - the text layout library will depend on external providers
>     for things like font installation lists, font metadata [...]

Pango has this implemented quite well afaik. Actually I like the
architecture of pango very much.

>   - no rendering support [...]

I don't get this. Rendering should be possible through some backends
like freetype and maybe others. How does underlining come in here,
expecially in a no-rendering context?

> PS: I suggest you to look at UCI for Berlin, since it's written
>     in C++ and works pretty well right now..

UCI? I know ICU (IBMs Components for Unicode). We started our own
unicode library because of some sticky licensing issues (which are now
resolved, ICU is under X-license). We might give up our own lib now.
But that does not solve our Fonthandling issues: We need something like
the virtual fonts pango has, we need to combine several unicode chars
into one glyph (ligature support), we need to do what pango calls glyph
shaping (arranging unicode characters to form a single glyph), we need
exact sizes for those glyphs and we might need to transform those glyphs
(replace a char by it's mirrored equivalent provided by the font, we
could do that by replacing chars in the string by their mirrored
equivalent, but I'd like to do that at this level if possible) and
finally render the result.

We don't need fancy unicode layout (Bidir and stuff), that happens
somewhere else, we don't need support for styles (just a way to switch
between diffrent fonts), we don't need any fancy string handling, ...

-- 
Gruss,
Tobias

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Tobias Hunger                  The box said: 'Windows 95 or better'
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