1215702 - remove backend-only CSS properties (marks, orphans, page, size, widows)

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

We currently have support for parsing and storage, but not computation, of 5 CSS properties (marks, orphans, page, size, widows).  Three of them were only ever intended to be used in @page rules and *not* in style rules.  Additionally we're violating the CSS specs by parsing them (and accepting them in @supports) when we don't actually support them.

We should just remove the code.  If we ever want to add some support for these properties, we can add the code back, without the complication of having to deal with half-implemented properties in the codebase (causing issues like bug 1215672).

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch 1 - Remove the CSS properties that use CSS_PROP_BACKENDONLY (marks, orphans, page, size, widows), i.e., properties that were added in early Gecko days but never actually implemented

We're violating http://www.w3.org/TR/CSS/#partial by leaving this
implementation in when we don't actually support the properties.

We're also incorrectly parsing marks and size in style rules rather than
@page rules; they were only intended for @page rules.

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch 2 - Remove the mechanism of backend-only CSS properties

This is a mechanism that should not exist; any use of it means
nonconformance with http://www.w3.org/TR/CSS/#partial .

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(I ran layout/style/test mochitests locally; they pass.)

Comment 4

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/d206c48d9e64
https://hg.mozilla.org/integration/mozilla-inbound/rev/eabe8e45ac29

Comment 5

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/d206c48d9e64
https://hg.mozilla.org/mozilla-central/rev/eabe8e45ac29

Comment 6

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/d206c48d9e64
https://hg.mozilla.org/mozilla-central/rev/eabe8e45ac29

Comment 7

[Kohei Yoshino]

Added the site compatibility doc just in case: https://www.fxsitecompat.com/en-US/docs/2015/several-unimplemented-css-properties-have-been-dropped/

Comment 8

[Jean-Yves Perrier [:teoli]]

I've updated:
https://developer.mozilla.org/en-US/Firefox/Releases/44#CSS
and make sure that we indicated that we don't support them on the pages of the three of these properties we have documentation for:
https://developer.mozilla.org/en-US/docs/Web/CSS/%40page/marks
https://developer.mozilla.org/en-US/docs/Web/CSS/orphans
https://developer.mozilla.org/en-US/docs/Web/CSS/widows