CSS

This is the Mozilla wiki home page for Cascading Style Sheets (CSS), one of several areas of Open Web Standards.

CSS

Platform priorities

The following CSS specs/proposals are a priority for the Platform.

2018 Priorities

These are *in progress* 2018 Priorities for CSS features in Firefox.

(currently being discussed at Yallhands in Austin, Texas)

• Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1424418
• Some public input: https://twitter.com/t/status/939273644043366400

Critical Fixes

Critical fixes to features or larger specs we already support (more important than new features in general)

• https://bugzilla.mozilla.org/show_bug.cgi?id=1398482
• List from DevRel kept here: http://mozdevs.github.io/devrel-dashboard/ in CSS and Layout sections

Fonts Level 4

For Variable Fonts support in particular:

• Bugzilla for Variable Fonts: https://bugzilla.mozilla.org/show_bug.cgi?id=1302685
• Fonts 4, metabug

(reprioritize Fonts Level 4 accordingly once we have Variable Fonts)

Motion Path

• Motion Path Module Level 1, meta bug

Sizing

CSS Intrinsic & Extrinsic Sizing Module Level 3 (WD) metabug

• intrinsic size keywords: fix #567039 & #1055887, and unprefix (#1322780

Shapes

• CSS Shapes (CR, another CR expected any moment now in 2017) metabug
  • shape-outside

Containment

• CSS Containment Module Level 1 (FPWD) 'contain' property, size/layout, style, paint. metabug

Scroll Anchoring

• [spec?] [metabug?]

Values and Units 3

CSS Values and Units Module Level 3 (CR) metabug

• [ ] calc() function in particular. metabug
• re-prioritize Values and Units 3 once calc fixes have landed.
• [ ] attr function (at risk) — very useful in combination with CSS Shapes, in the context of a CMS

SVG properties in CSS

This bit from SVG2:

• 1383650: Implement SVG geometry properties in CSS

Grid Level 2

Grid Level 2 AKA subgrid (use-cases, a11y implications)

• CSS Grid level 2 specifically for subgrid
• doing some exploratory implementing, design may (hopefully likely) change accordingly
• see also for quick use-cases / tutorial:
  • http://fantasai.inkedblade.net/style/discuss/subgrid-markup/

Media Queries 4

• Media Queries 4 (note: new features in 4), metabug
  • full support of numerical comparators (<, <=, =>, >)
  • expansion of negation syntax (and, or, not)
  • interaction features #1035774
  • 2017-08-02 CSSWG resolved to take to CR
  • Also prefers-reduced-motion from Level 5 (#1365045)

Inline Layout

• CSS Inline Layout Module Level 3 (TR WD), metabug
  • focusing for now on CSS Initial-letter related features (initial-letter * metabug)
    • one (implementation design) blocker issue: https://github.com/w3c/csswg-drafts/issues/743

Scrollbar Styling

Spec in editor's draft - many requests for this

• https://drafts.csswg.org/css-scrollbars-1/

Multi-column

• CSS Multi-column Layout (TR WD), metabug
  • unprefixing, column-span, a11y bug hack removal, column-break
  • Alias page-break-* to break-*: https://bugzilla.mozilla.org/show_bug.cgi?id=775618

(Jen has a demo of bugs / test page at http://labs.jensimmons.com/examples/multicolumn-3-bug-demo.html)

Box Alignment

• CSS Box Alignment (WD), metabug
  • all properties for blocks (e.g. 1105571)
  • and some details for flexbox (see metabug 1105570 Depends on)
  • spec CR depends on resolving open css-align-3 issues

Container Queries Prerequisites

There's a lot of anecdotal demand for Container Queries / Element Queries. See replies here:

• https://twitter.com/t/status/939273644043366400

We should at least figure out what features / bug fixes we would need to address to even consider something like Container Queries (which we should also give input on)

• RICG cq-usecases: https://github.com/ResponsiveImagesCG/cq-usecases (Requirements section? #36)
• one proposal: https://tomhodgins.github.io/element-queries-spec/element-queries.html

Scroll Snap update

• Scroll Snap (CR), metabug
  • Fix related bugs

CSS Color Level 4

CSS Color Module Level 4 (ED), metabug

• Color improvements (wide gamut, color correction, note CSS color correction preffed off)

Implement correct color management of CSS colors (which is really earlier levels of CSS color).

CSS Images 3

• CSS Images Module Level 3
• [Meta bug https://bugzilla.mozilla.org/show_bug.cgi?id=703431]
• cross-fade() -- particularly relevant when animating between images
• image-orientation:none
• image-rendering: pixelated
• position syntax in radial-gradient()

2018 Lower Priorities

Features or areas that distinctly got lower support during Yallhands Layout team prioritization discussions.

Better Print Support

Start looking at what specs and features would significantly improve print support. Much of this is testing and bugfixing edgecases of existing features, some of it may require or benefit from new specs/features.

• CSS Paged Media Module Level 3 (old 2013 WD) metabug

More specs / features in particular TBD.

text-decoration-skip

• Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=812990
• parity with Chrome

Actively Implementing

Beyond the above priorities, we should continue to actively implement, fix bugs on the following:

• Stylo (metabug)

Flexbox

Mozilla has a pretty solid complete Flexbox (W3C CR, just waiting on feature-interaction tests to go PR) implementation. We are working on some fixes to make it even better, e.g.

• Metabug for to-be-implemented spec changes

Grid

• CSS Grid (CR) metabug
  • lots of work

3D Transforms

• 3D Transform interop / spec changes, 3D transform bugs

Masking

• CSS Masking (W3C CR), metabug
  • another clip-path ticket — path(): https://bugzilla.mozilla.org/show_bug.cgi?id=1246764

Text Decoration

CSS Text Decoration Module Level 3 (2013 CR) (metabug), e.g.:

• focusing on text-decoration-skip https://bugzilla.mozilla.org/show_bug.cgi?id=812990
• text-emphasis (remaining bugs)
• text-underline-position
• What else left for this module? (JS)
  • See "Depends on" in metabug 1221864 (TÇ)

Writing Modes

CSS Writing Modes Level 3 (2015 CR) (metabug)

• 2017-08-04 CSSWG Resolved to publish an updated CR

Fonts Level 3

Wrap-up the few remaining bugs, or declare that we're done (e.g. font-variant as a descriptor?)

• Fonts 3, metabug

Under the hood and related

• Intersection observer (Intent to ship thread)
• Resize observer (intent to implement coming)
• Web Animations API (metabug)

Evaluating

Font Rendering Controls

CSS Font Rendering Controls Module Level 1 (ED)

• focusing on font-display descriptor https://bugzilla.mozilla.org/show_bug.cgi?id=1317445 (implemented behind a flag, other browsers too)

Font Loading

CSS Font Loading Module Level 3 https://developer.mozilla.org/en-US/docs/Web/API/CSS_Font_Loading_API shipped in 41

• CSS Font Loading Improvements, Multiple bugs

Other

• font inflation removed
• CSS Transform properties (shorthands)

Related HTML5

HTML5 layout and presentation related work:

• srcset intrinsic size
• ...

Recent CRs

Cascading and Inheritance

• CSS Cascading and Inheritance Level 3 (CR), metabug
  • New features since CSS2.x
    • scoped styles, animations, and transitions in the cascade.

Upcoming CRs

These CRs are expected in 2017:

For all potential CRs:

• Which browsers have openly announced implementations or intent to implement? (links?)

• Box Alignment (see above)

Text Level 3

• Text (need list of changes since CSS 2.1), metabug

Selectors 4

Selectors 4 (need list of changes since 3), metabug

• No explicit dependency on Stylo, just lower priority
• Selectors4 remaining features
  • CSS ::selection fixes + unprefixing
  • ... remaining new features? (JS)

Shipping Soon

As the above priorities get implemented, moving down here to note we're waiting for them to ship.

Image Values and Replaced Content

[1] (CR)

• image() function
• [ ] xywh fragment syntax

Style sheet APIs for Add-ons

• style sheet APIs in add-ons SDK / loading async APIs (to be handled by stylo)

Filter Effects Level 2

• Filter Effects Module Level 2: backdrop-filter
  • backdrop-filter bug (caniuse: only Safari supports)
  • also on Trello Future Backlog

Device Adaptation

CSS Device Adaptation Module Level 1 (WD)

Houdini

• CSS Houdini - see inside for Houdini implementation thoughts/plan

properties

Please add subpages for each (unprefixed) CSS property in alphabetical order.

• ...
• overflow
• ...
• text-overflow
• ...

in development

CSS properties which have not yet made it to a Candidate Recommendation (or later), or are only implemented in the wild in prefixed form.

new pseudo-classes

• ...
• :autofill
• ...

new properties

• ...
• text-size-adjust (-moz-, -ms-, -webkit-)
• ...

See Also

• CSS/
• CSS/:autofill
• CSS/Houdini
• CSS/text-overflow
• CSS/text-size-adjust

• CSS3
• HTML5
• Standards
• MDN: CSS home page
• Mozilla DevRel Dashboard - dynamic overview of [META] and other high level bugs in CSS, DOM, DevTools, MDN, Toolkit, etc.
• CSS Working Group Wiki