"small" "normal" "big" values of mathsize

[fred-wang]

The proposal is to remove/deprecate these attribute values.

In any case "small" and "big" values are NOT accurately specified:
"The values "small" and "big" choose a size smaller or larger than the current font size, but leave the exact proportions unspecified; "normal" is allowed for completeness, but since it is equivalent to "100%" or "1em", it has no effect. "

[physikerwelt]

See also #4

[fred-wang]

MathML Core does not really define mathsize yet, but the schema currently mentions these values.

[fred-wang]

cc @rwlbuis, @emilio :

The values were removed from the MathML schema in w3c/mathml-core@bbc0f8a ; we agreed not to add them back to core.

I'm leaving this open because it still remains to:

• Remove WPT tests if any.
• Send intent-to-remove to mozilla/webkit-dev mailing lists (maybe old Math WG too?).
• Remove browser implementation.
• Decide what to do for the full MathML spec (remove values? deprecate them? specify explicit numbers?).
• Add polyfill to https://github.com/mathml-refresh/mathml-polyfills (e.g. convert to mathsize="NUMBER%").

[fred-wang]

Decision is to keep in MathML full but note in main spec that non core features will require polyfills so you may not want to use them. https://lists.w3.org/Archives/Public/public-mathml4/2019Mar/0026.html

[fred-wang]

Resolution:

• "small" "normal" "big" values of mathsize #7 (comment)

Specification:

• Add a deprecation warning in Full?

Implementation:

• WebKit: https://bugs.webkit.org/show_bug.cgi?id=197493
• Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1548527
• Not implemented in Chromium.

Polyfill:

• Map them to numeric lengths.
• Maybe use CSS variables for user customization?

Tests:

• Remove WPT tests or check that these values are not supported.

[NSoiffer]

MathPlayer uses the values: 0.8, 1.0, 1.25 for small, normal, big, respectively.

Note: specification of mathsize takes priority over fontsize.

[fred-wang]

These are not in core ( #7 (comment) ) ; @davidcarlisle can you please check full and update it if needed?

[NSoiffer]

MathJax uses the values 0.71, 1, 2 for small, normal, big, respectively.

[fred-wang]

WebKit uses values 0.75em, 1em and 1.5em:
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/mathml/MathMLElement.cpp#L101

Firefox uses the keyword "small", "medium", "large":
https://searchfox.org/mozilla-central/source/dom/mathml/nsMathMLElement.cpp#553
which at the end uses scaling factor 8/9, 1, 6/5:
https://searchfox.org/mozilla-central/source/servo/components/style/values/specified/font.rs#692

As specified in https://drafts.csswg.org/css-fonts-3/#font-size-prop

I think it makes sense for a CSS-based polyfill to use font-size keyword "small", "medium", "large" so that the scaling factor is up to the browser and consistent with CSS.

[samdooley]

Here are the values I used the last time I looked at this (pre-2011, at least)
"xx-small": "60%", //
"x-small": "75%", //
"small": "80%", //
"medium": "100%", //
"large": "120%", //
"x-large": "150%", //
"xx-large": "200%", //
"xxx-large": "300%", //
I do not know what source I used to choose these values.

[fred-wang]

The proposal we had in previous meeting was to set this in MathML full:

• Map small to CSS x-small ( 3/4 )
• Map normal to CSS medium ( 1)
• Map big to CSS x-large ( 3/2 )

[fred-wang]

https://lists.w3.org/Archives/Public/public-mathml4/2019Jun/0013.html

ADOPTED Mapping to CSS’s values for x-small (¾), medium (1), and x-large
(3/2)

[fred-wang]

Test landed: web-platform-tests/wpt#18037

I'm closing this since the remaining work is in implementation (native or polyfill)

[fred-wang]

Polyfill:

window.addEventListener("load", function() {
    const namespaceURI = "http://www.w3.org/1998/Math/MathML";
    Array.from(document.body.
               getElementsByTagNameNS(namespaceURI, "*")).
        forEach(element => {
            if (!element.hasAttribute("mathsize"))
                return;
            var value = element.getAttribute("mathsize").
                replace(/small|normal|big/, match => {
                    switch (match) {
                    case "small": return "75%";
                    case "normal": return "100%";
                    case "big": return "150%";
                    }
                });
            element.setAttribute("mathsize", value);
        });
});