Re: [Silgraphite-devel] changing bidi

[Martin H. <mar...@si...>]

Dear Cambell,

> Is the first paragraph supposed to read 'unable to do'

No. Graphite can, and actually, after my refactoring, is still able to do paragraph level full bidi processing. But there are limitations: 1. all the characters that occur in the paragraph must be supported by the one font for that paragraph. 2. The whole paragraph has to be passed to graphite because the bidi algorithm needs access to the whole paragraph, you can't pass it part of a paragraph and expect it to work out where it is in the nested depths of embedded isolating ranges of left to right text within right to left within left to right and so on.

For this reason, I am considering deprecating the full bidi support in the graphite engine. The upcoming 1.3.1 release will still support full bidi for those that use it. But I know of no use cases where it is used. In all the cases I see, applications do their own bidi analysis at the paragraph level and then break that into runs of equal direction and font and pass those runs as mono direction runs to Graphite. This is the same that happens for things like Harfbuzz.

The only two cases where people may cry if we remove bidi are:

1. They are using Graphite to do full bidi at the paragraph level.
2. They have fonts with PUA characters in with non L bidi behaviour, that they want to represent.

In the latter case, we may be able to help such people, but there will still be limitations brought on by graphite only having access to a small window of a paragraph.

If you are a user of Graphite and fall into either of the above 2 categories, then I would like to hear from you.

TIA,
Yours,
Martin

> 
> C
> On 28/08/2015 12:29 pm, "Martin Hosken" <mar...@si...> wrote:
> 
> > Dear All,
> >
> > We've got bidi wrong and need to fix it. In order to facilitate doing
> > things right moving forward I need to know of any applications that are
> > using the graphite library that are passing graphite a complete paragraph
> > and expecting graphite to do full bidi on that paragraph (which currently
> > it is able to do).
> >
> > Of course I would also love to know of any applications out there that are
> > using the graphite library directly. So if you want to confess, now is a
> > good time :)
> >
> > Yours,
> > Martin
> >
> >
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