Re: New RTL math support in MathML Core / Chromium browsers

Thank you, Frédéric, for the background.

This question is obviously not a critique of the present work, but rather
from an interest in high quality typography and digital ink rendering.
 What you say is very helpful.

Stephen

On Tue, Jul 22, 2025 at 12:30 PM Frédéric Wang <fwang@igalia.com> wrote:

> Hi Stephen,
>
> The mirroring for stretchy math operator we added in MathML Core was just
> to do the same technique that exists for normal text (see section HTML RTL
> mirroring at
> https://people.igalia.com/fwang/mathml-operator-mirroring-explainer.html).
> So basically we mirror the base glyph and then apply to the mirrored glyph
> the stretching rules that are described in OpenType MATH / TeX which only
> uses size variants or glyph assembly. This approach is probably not
> flexible enough for the Arabic case.
>
> There is a separate issue about using variable fonts to get better
> stretchy operator support which I believe would better address the use case
> you are mentioning but I believe we lack some data in OpenType MATH before
> we can do that in MathML Core:
> https://github.com/w3c/mathml-core/issues/122
>
> Frédéric Wang
> Le 22/07/2025 à 14:31, Stephen Watt a écrit :
>
> I had one question, independent of this superb achievement, related to
> glyph rendering:
>
> In many math symbols we have varying width strokes that look as though
> they are stylistic imitations of using a chisel-edge pen.   In these,
> stroke thickness depends on stroke orientation.
>
> So the question is:  Does glyph mirroring provide rendering where the
> strokes in square roots, etc,  are consistent with the kashida, ijam, etc
> in fonts with varying stroke width?
>
> Stephen
>
> On Tue, Jul 22, 2025 at 8:31 AM Stephen Watt <smwatt@gmail.com> wrote:
>
>> This is fantastic.   Yes, very hearty congratulations!
>>
>> Stephen
>>
>> On Tue, Jul 22, 2025 at 6:20 AM Deyan Ginev <deyan.ginev@gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> Congratulations to Harry and Eri for landing this upgrade!
>>> And best of success with your continuing MathML Core work.
>>>
>>> Greetings,
>>> Deyan
>>>
>>>
>>> On Tue, Jul 22, 2025 at 5:45 AM Frédéric Wang <fwang@igalia.com> wrote:
>>>
>>>> Here is the attachment.
>>>>
>>>> Le 22/07/2025 à 11:39, Frédéric Wang a écrit :
>>>> > Hello,
>>>> >
>>>> > As some of you probably know, last year Harry Chen had experimented
>>>> > RTL math support in Chromium as part Igali's Coding Experience
>>>> > Program. This is just a heads up that I merged his spec changes last
>>>> > week. My colleague Eri took over the work and landed a patch in
>>>> Chromium.
>>>> >
>>>> > You can find the explainer and Chromium's intent to prototype here:
>>>> >
>>>> >
>>>> https://people.igalia.com/fwang/mathml-operator-mirroring-explainer.html
>>>> >
>>>> > https://groups.google.com/a/chromium.org/g/blink-dev/c/iU0jQWJZCEM
>>>> >
>>>> > Support is available in the latest Chrome Canary if you enable
>>>> > experimental web platform features from about:flags (see attached
>>>> > screenshot).
>>>> >
>>>> > WebKit operator mirroring is known to be quite limited. Firefox has
>>>> > some implementation, but we noticed it currently has some issues. So
>>>> > we will make progress on them before sending the intent to ship to
>>>> > Chromium.
>>>> >
>>>> > Frédéric Wang
>>>> >
>>>> >
>>>
>>>