Background
MediaWiki core currently includes Less mixins .horizontal-gradient() and vertical-gradient() that were originally added to simplify the use of horizontal gradients across browsers due to vendor prefixes. At the time of introduction, this abstraction helped handle inconsistencies in vendor implementations of CSS gradients.
As of MediaWiki 1.43, this mixin has been explicitly marked as deprecated with a note to use linear-gradient directly. All major browsers have long supported unprefixed gradients, making the mixin redundant. Keeping it in MediaWiki core creates unnecessary technical debt and risks developers continuing to rely on deprecated abstractions instead of standard CSS.
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Goal
- Identify and confirm all current usages of .horizontal-gradient() and .vertical-gradient() within MediaWiki core and bundled skins/extensions.
- Replace any existing calls to the mixins with direct linear-gradient( to right, … ) declarations.
- Remove the mixin definition file from MediaWiki core.
- Ensure that no regressions occur in styles that previously relied on these helpers.
Acceptance criteria for done
- All references are replaced with direct CSS standard linear-gradient() usage.
- .horizontal-gradient() and .vertical-gradient() mixin are removed from 'mediawiki.mixins.less'.
- No styling regressions are introduced in MediaWiki core, or bundled skins and extensions.