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Re: [font-metrics-api] font data versus typographic layout results

From: Alan Stearns <stearns@adobe.com>
Date: Fri, 14 Aug 2015 14:26:26 +0000
To: Chris Lilley <chris@w3.org>, Peter Krautzberger <peter.krautzberger@mathjax.org>
CC: "public-houdini@w3.org" <public-houdini@w3.org>, John Daggett <jdaggett@mozilla.com>
Message-ID: <D1F346D3.2C185%stearns@adobe.com>
On 8/14/15, 4:46 AM, "Chris Lilley" <chris@w3.org> wrote:

>Hello Alan, Peter
>
>(again apologies for the delayed reply)
>
>Thursday, July 30, 2015, 4:23:09 PM, you wrote:
>
>> On 7/30/15, 7:15 AM, "Peter Krautzberger"
>><peter.krautzberger@mathjax.org>
>>>It looks like this would provide some global font metrics, but not the
>>>metrics of individual characters/strings. Is that correct?
>>>
>>>That would be helpful, particularly the baseline information, but it
>>>would not be sufficient for a use case like mathematical layout.
>
>> Not global - it’s giving the results from the first line box.
>
>Would there be a way to iterate over the line boxes, under your
>proposal?

There are ways of iterating through fragments in the box tree API.

>
>>  But you are
>> correct, this would not be sufficient for mathematical layout. It’s a
>>step
>> towards what you need, satisfying simpler use cases.
>
>I agree it might satisfy simpler use cases, but unless it is
>extensible to cover the mathematical layout use case it is not a step
>towards enabling it - it is a step in a different direction that does
>not address the use case.

I’m assuming we’ll come up with something like a DeadRange that also
supports returning some DeadFontMetrics. With sufficiently small ranges
you can sample the typographic layout results for single glyphs, which is
another step closer to what’s needed for mathematical layout. We’d need to
add width or advance information, which would be a simple addition to
DeadFontMetrics. I expect there will be a few more things to add, but I
think there’s a way to get to everything that’s needed for mathematical
layout.

Thanks,

Alan

Received on Friday, 14 August 2015 14:27:23 UTC

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