Open Bug 1328475 Opened 4 years ago Updated 4 months ago
Give "-moz-user-select:auto" special spec-defined inheritance-like computation behavior
Right now, -moz-user-select:auto (the initial value) simply computes to "auto" (which can be observed via getComputedStyle). But the css-ui-4 spec changed in 2015, to require that "auto" always compute to something else. Here's that change: https://github.com/w3c/csswg-drafts/commit/1c0b6c94a9659d5dcfbfb888344e48821bd73898 The current spec-text is as follows: ==== auto The computed value of auto is determined as follows: * On the ::before and ::after pseudo elements, the computed value is none * If the element is an editable element, the computed value is contain * Otherwise, if the computed value of user-select on the parent of this element is all, the computed value is all * Otherwise, if the computed value of user-select on the parent of this element is none, the computed value is none * Otherwise, the computed value is text Note: This unusual combination of a non inherited property with an initial value of auto whose computed value depends on the parent element makes it possible to create what is effectively selective inheritance. This was initially proposed by Microsoft in IE to introduce a behavior similar to inheritance except that the contain value does not inherit. ==== Spec reference: https://drafts.csswg.org/css-ui-4/#valdef-user-select-auto
For reference/context, here's a github issue with some back-and-forth about this spec text (which eventually settled on keeping the behavior quoted in comment 0): https://github.com/w3c/csswg-drafts/issues/336
Summary: Give "-moz-user-select:auto" special spec-defined computation behavior → Give "-moz-user-select:auto" special spec-defined inheritance-like computation behavior
See Also: → https://webcompat.com/issues/13859
Webcompat Priority: --- → ?
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