1416564 - Try to remove the mozmm CSS unit

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement, P3)

Description

[Emilio Cobos Álvarez (:emilio)]

It's used only on a handful of tests, and not in any spec. That sounds like an intent to unship to me.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1416564: Remove mozmm CSS unit.

Review commit: https://reviewboard.mozilla.org/r/198940/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/198940/

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 8927663 [details]
Bug 1416564: Remove mozmm CSS unit.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/198940/diff/1-2/

Comment 3

[Emilio Cobos Álvarez (:emilio)]

(Was going to ask dbaron for review too, but he's not currently accepting requests)

Comment 4

[Cameron McCormack (:heycam)]

Comment on attachment 8927663 [details]
Bug 1416564: Remove mozmm CSS unit.

https://reviewboard.mozilla.org/r/198940/#review204424

::: dom/interfaces/base/nsIDOMWindowUtils.idl:83
(Diff revision 2)
>     * Cannot be accessed from unprivileged context (not content-accessible)
>     */
>    readonly attribute boolean docCharsetIsForced;
>  
>    /**
> +   * Return a the conversion of a physical millimeter in CSS pixels.

s/a the/the/

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ab20e3b3ef7b
Remove mozmm CSS unit. r=heycam

Comment 6

[Ionuț Goldan [:igoldan]]

It looks like this reduced our build times on Windows:

== Change summary for alert #10551 (as of Tue, 14 Nov 2017 13:11:45 GMT) ==

Improvements:

  8%  build times summary windows2012-64-rusttests opt taskcluster-c4.4xlarge     2,561.31 -> 2,360.03
  6%  build times summary windows2012-32 opt taskcluster-c4.4xlarge               2,838.70 -> 2,666.70
  5%  build times summary windows2012-64 opt static-analysis taskcluster-c4.4xlarge2,784.12 -> 2,643.45
  5%  build times summary windows2012-32 opt static-analysis taskcluster-c4.4xlarge2,674.80 -> 2,544.93

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=10551

Comment 7

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/ab20e3b3ef7b

Comment 8

[Emilio Cobos Álvarez (:emilio)]

(In reply to Ionuț Goldan [:igoldan], Performance Sheriffing from comment #6)
>   8%  build times summary windows2012-64-rusttests opt
> taskcluster-c4.4xlarge     2,561.31 -> 2,360.03
>   6%  build times summary windows2012-32 opt taskcluster-c4.4xlarge         
> 2,838.70 -> 2,666.70
>   5%  build times summary windows2012-64 opt static-analysis
> taskcluster-c4.4xlarge2,784.12 -> 2,643.45
>   5%  build times summary windows2012-32 opt static-analysis
> taskcluster-c4.4xlarge2,674.80 -> 2,544.93

I'm as fascinated by that as bug 1416741, but I guess the "-mozmm" special-case string check in style_derive every dimension was somehow slow on windows? shrug

Comment 9

[Kohei Yoshino [:kohei]]

Posted the site compatibility note: https://www.fxsitecompat.com/en-CA/docs/2017/mozmm-css-unit-is-no-longer-supported/

Comment 10

[Chris Mills [:cmills]]

I have documented this on MDN, by:

* Adding a note to the Fx59 rel notes: https://developer.mozilla.org/en-US/Firefox/Releases/59#CSS_2
* Describing the change in appropriate places on https://developer.mozilla.org/en-US/docs/Web/CSS/length

Let me know if that looks OK. Thanks!

Comment 11

[Felix Miata]

Attachment: http://fm.no-ip.com/Css/mozmm.css

Removing this valuable reason for preferring mozilla-based browsers to non-mozilla web browsers broke approximately 67 of my web pages using this stylesheet, and 172 of my web pages using the mozmm unit in their head and/or inline styles.

Many of these, maybe most, were constructed or reconstructed following the breakage of CSS version 3 by the removal of absolute units to take advantage of the unique workaround provided by the mozmm unit.

CSS specs provide no means AFAICT for any of these to be repaired.