- From: Jason via GitHub <noreply@w3.org>
- Date: Sun, 15 Mar 2026 22:21:45 +0000
- To: public-css-archive@w3.org
CGQAQ has just created a new issue for https://github.com/w3c/csswg-drafts: == [css-masking] Add mask-position-x and mask-position-y longhands == CSS Backgrounds 4 defines `background-position-x`, `background-position-y`, `background-position-inline`, and `background-position-block` as longhands of `background-position` ([§2.6](https://drafts.csswg.org/css-backgrounds-4/#background-position-longhands)). CSS Masking 1 defers to CSS Backgrounds for its property definitions, and `mask-position` is defined analogously to `background-position`. However, the corresponding longhands `mask-position-x` and `mask-position-y` are not specified. We'd like to add these for consistency. Reasons: 1. **Parity with background-position:** Authors can already set `background-position-x` and `background-position-y` independently. The same use case applies to masks — e.g. animating only the horizontal position of a mask without affecting the vertical. 2. **Existing implementations:** Chromium and WebKit have shipped `-webkit-mask-position-x` and `-webkit-mask-position-y` for many years. Standardizing unprefixed versions lets us align implementations and eventually deprecate the prefixed forms. 3. **Animation use case:** Animating a single axis of a position is a common pattern. Without longhands, authors must animate the full `mask-position` shorthand even when only one axis changes, which is less ergonomic and harder to compose with other animations. Should these be added to CSS Masking 1 (or a future level), mirroring the CSS Backgrounds 4 longhands? Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13660 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Sunday, 15 March 2026 22:21:47 UTC