Re: [css-houdini-drafts] [css-typed-om] Can we avoid property-specific reification rules for most cases? (#1159)

In Gecko, we’re implementing Typed OM reification through a generic ToTyped trait that’s derived for most style value types. Right now this covers keyword values, which are reified automatically as CSSKeywordValue objects.

Work is in progress to extend this to numeric types, which will reify as CSSNumericValue, etc. and eventually to other categories such as colors and transforms. The derive system is designed so that most types can be handled automatically, while still allowing explicit impl ToTyped definitions for special or complex cases.

This approach already follows the “type-based reification” model you describe? The mapping is determined by value type rather than property name, so new properties generally require no additional reification code (only if there's no suitable value type).

Here are some links:
https://searchfox.org/firefox-main/rev/644f0db17749554fe23a45b43e77e61f42acdfd9/servo/components/style_traits/values.rs#597
https://searchfox.org/firefox-main/rev/644f0db17749554fe23a45b43e77e61f42acdfd9/servo/components/style_derive/to_typed.rs#12
https://searchfox.org/firefox-main/rev/644f0db17749554fe23a45b43e77e61f42acdfd9/servo/components/style/properties/mod.rs#142

https://bugzilla.mozilla.org/show_bug.cgi?id=1991631


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Received on Wednesday, 15 October 2025 12:08:11 UTC