w3c / w3c/csswg-drafts

[css-backgrounds] background-position definition doesn't reflect reality.

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Description

https://drafts.csswg.org/css-backgrounds/#background-position doesn't mention at all background-position-x or background-position-y, of which background-position is a shorthand of.

These properties should be defined. For example, Gecko accepts background-position-y: <keyword> <length>? (due to the legacy 3-value syntax) while Blink / WebKit don't.

cc @ericwilligers, you did some yak-shaving re. 3-value position syntax and such, do you know which syntax does background-position-* accept in Blink?

Is there any plan to avoid supporting the three-value positions in background-position as well?

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the CSS Backgrounds specification section at https://drafts.csswg.org/css-backgrounds/#background-position and review the definitions of background-position, background-position-x, and background-position-y. Check the issue's discussion of Gecko, Blink, and WebKit syntax; done means the relevant properties and accepted syntax are clearly defined and the three-value behavior question is resolved.

Written by the indexing model from the issue text.

Assessment

Tech stack
css
Domain
documentation
Issue type
Documentation
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
28/100

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