1574749 - Remove support for nonzero unitless lengths

Status: RESOLVED FIXED

(Core :: MathML, defect)

Description

[Frédéric Wang (:fredw)]

MathML says that things like linethickness="5" should be interpreted as 500%. This diverges from CSS which only accepts "0" and interpret it as pixels. The MathML CG agreed to remove this: https://github.com/mathml-refresh/mathml/issues/7

Comment 1

[Frédéric Wang (:fredw)]

Attachment: Bug 1574749 - Remove support for nonzero unitless lengths. r=emilio

See https://github.com/mathml-refresh/mathml/issues/24
and https://groups.google.com/forum/#!topic/mozilla.dev.platform/-yV6wb3klSA

This commit introduces a new preference option
mathml.nonzero_unitless_lengths.disabled to disable MathML nonzero unitless
values like "5" for 500%. MathML nonzero unitless are now disabled by default
but it could be easily enabled again later if we decide otherwise.

• test_bug553917.html is updated to check that these values now cause an error
  message to be logged into the console rather than a deprecated warning.
  Additionally, the test checking invalid double dots "2..0" is updated to
  not use unitless syntax.
• The old test 355548-3.xml checks support for mathsize names and also uses
  several features that are going to be deprecated. So it is just run with
  the proper preference adjustment.
• mfrac-linethickness-2.xhtml and number-size-1.xhtml check support for
  unitless lengths so they are now run with that support enabled.
• Failure expectations for WPT tests frac-linethickness-001.html and
  lengths-1.html are remove now that we pass these tests.
  We get more assertion passing for the "Legacy numbers" test of
  lengths-2.html ; however there are still some issues to address
  (see bug 1574751).

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e45398b51329
Remove support for nonzero unitless lengths. r=emilio

Comment 3

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/e45398b51329

Comment 4

[Frédéric Wang (:fredw)]

For the dev doc: For any nonzero number x, the unitless value ${x} can be replaced with ${y}% where y = 100 * x. For example "2" can be replaced with "200%".

Comment 5

[Kohei Yoshino [:kohei]]

Posted site compatibility note: https://www.fxsitecompat.dev/en-CA/docs/2019/various-legacy-mathml-features-have-been-deprecated-or-removed/

Comment 6

[Paul Masson]

In Firefox 69 I'm getting a warning when setting linethickness="0" on mfrac for binomial coefficients. Shouldn't a plain zero be allowed here? Will this behavior change with version 70? Thanks.

Comment 7

[Frédéric Wang (:fredw)]

(In reply to Paul Masson from comment #6)

In Firefox 69 I'm getting a warning when setting linethickness="0" on mfrac for binomial coefficients. Shouldn't a plain zero be allowed here? Will this behavior change with version 70? Thanks.

I think warning "Unitless values are deprecated in MathML 3." for lengths equal to "0" have been sent since 553917 because MathML3 suggests to always use explicit unit instead: https://www.w3.org/TR/MathML3/chapter2.html#fund.units

MathML Core aligns with CSS, so a unitless zero is acceptable. I guess we should remove the warning if it is still present.

Comment 8

[Florian Scholz (Open Web Docs)]

Removed mentions of unitless values on:

• https://developer.mozilla.org/en-US/docs/Web/MathML/Attribute
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mstyle
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mi
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mn
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mo
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/ms
• https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mtext

Added to Fx70 release notes:
https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/70#MathML