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List: webkit-dev
Subject: Re: [webkit-dev] Implementing MathML stylistic attributes in WebKit
From: Ryosuke Niwa <rniwa () webkit ! org>
Date: 2020-09-28 23:45:52
Message-ID: CABNRm63QeYJZBYGvnyrYjUFiYD3hUme+PX9MKZ_YNZ9z=8SODQ () mail ! gmail ! com
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On Fri, Sep 25, 2020 at 12:47 AM Frédéric Wang <fwang@igalia.com> wrote:
> On 02/09/2019 16:11, Frédéric Wang wrote:
>
> Hello,
>
> Currently MathML attributes mathvariant, displaystyle and scriptlevel [1]
> [2] are implemented in WebKit using custom "style resolution" and
> "one-glyph rendering" inside the MathML layout code [3] [4] [5]. These
> features involve text rendering and interaction with CSS font-size, so it
> is difficult to implement them properly and completely that way. There are
> known bugs and missing features right now (e.g. mathvariant transform only
> applies to one-character strings, automatic displaystyle/scriptlevel does
> not work with fractions, etc)
>
> Hi,
>
> An update on this, we have been discussing these and new properties with
> the CSSWG:
>
> https://github.com/w3c/csswg-drafts/issues/5384
>
> The math-depth / math-style CSS properties are being implemented in
> Chromium and renamed/exposed/tweaked in Gecko:
>
> https://mathml-refresh.github.io/mathml-core/#the-math-style-property
>
>
> https://mathml-refresh.github.io/mathml-core/#the-math-script-level-property
>
> So it makes sense to implement them in WebKit (it seems we still don't
> have a "intent to" mechanism, but people can follow
> https://bugs.webkit.org/show_bug.cgi?id=195797).
>
> The CSSWG is fine with a new text-transform value for automatic italic but
> using it for other values is controversial (see
> https://github.com/w3c/csswg-drafts/issues/3775). So if we want to
> preserve backward compatibility and fix existing bugs with mathvariant, we
> should probably re-implement it using an internal math-transform property
> (like what Gecko does) which according to our previous discussion is
> nowadays possible in WebKit.
>
Adding the support for new properties sounds good! My concern here is
really only about backwards compatibility.
- R. Niwa
[Attachment #5 (text/html)]
<div dir="ltr"><div dir="ltr"><br clear="all"><div><div dir="ltr" \
class="gmail_signature" data-smartmail="gmail_signature">On Fri, Sep 25, 2020 at \
12:47 AM Frédéric Wang <<a \
href="mailto:fwang@igalia.com">fwang@igalia.com</a>> \
wrote:<br></div></div></div><div class="gmail_quote"><blockquote class="gmail_quote" \
style="margin:0px 0px 0px \
0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div>
<div>On 02/09/2019 16:11, Frédéric Wang
wrote:<br>
</div>
<blockquote type="cite">
<div id="gmail-m_5046908447930718334magicdomid4"><span>Hello,</span></div>
<div id="gmail-m_5046908447930718334magicdomid5"><br>
</div>
<div id="gmail-m_5046908447930718334magicdomid6"><span>Currently
MathML attributes mathvariant, displaystyle and scriptlevel
[1] [2] are implemented in WebKit using custom "style
resolution" and "one-glyph rendering" inside the MathML \
layout code [3] [4] [5]. These features involve text rendering and
interaction with CSS font-size, so it is difficult to
implement them properly and completely that way. There are
known bugs and missing features right now (e.g. mathvariant
transform only applies to one-character strings, automatic
displaystyle/scriptlevel does not work with fractions, etc)</span></div>
</blockquote>
<p>Hi,</p>
<p>An update on this, we have been discussing these and new
properties with the CSSWG: <br>
</p>
<p><a href="https://github.com/w3c/csswg-drafts/issues/5384" \
target="_blank">https://github.com/w3c/csswg-drafts/issues/5384</a></p> <p>The \
math-depth / math-style CSS properties are being implemented in Chromium and \
renamed/exposed/tweaked in Gecko:<br> </p>
<p><a href="https://mathml-refresh.github.io/mathml-core/#the-math-style-property" \
target="_blank">https://mathml-refresh.github.io/mathml-core/#the-math-style-property</a></p>
<p><a href="https://mathml-refresh.github.io/mathml-core/#the-math-script-level-property" \
target="_blank">https://mathml-refresh.github.io/mathml-core/#the-math-script-level-property</a></p>
<p>So it makes sense to implement them in WebKit (it seems we still
don't have a "intent to" mechanism, but people can follow
<a href="https://bugs.webkit.org/show_bug.cgi?id=195797" \
target="_blank">https://bugs.webkit.org/show_bug.cgi?id=195797</a>).</p> <p>The \
CSSWG is fine with a new text-transform value for automatic italic but using it for \
other values is controversial (see
<a href="https://github.com/w3c/csswg-drafts/issues/3775" \
target="_blank">https://github.com/w3c/csswg-drafts/issues/3775</a>). So if we want \
to preserve backward compatibility and fix existing bugs with
mathvariant, we should probably re-implement it using an internal
math-transform property (like what Gecko does) which according to
our previous discussion is nowadays possible in \
WebKit.<br></p></div></blockquote><div>Adding the support for new properties sounds \
good! My concern here is really only about backwards \
compatibility.</div><div><br></div><div>- R. Niwa</div><div><br></div></div></div>
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