Allow types generated with prop_extractor! to implement Hash, PartialEq, and Eq trivially
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…alEq, Eq trivially Implements `Hash`, `PartialEq` and `Eq` on `ExtratorField` where `R::Type` also implements that trait, and enables the `prop_extractor!` macro to accept zero or more attributes preceding the type definition. Rationale: Makes implementing these traits as simple as it would be in an ordinary `struct` declaration. Use-case: In my particular case, I have some expensive-to-recompute bezier paths which are computed once in my `View`'s `layout` function; and some relatively trivial to recompute coordinates that change more often, and indicator which points to some position on those paths. By keeping a hash of those properties that could require recomputation of the path (line size, component size, things like that) I can avoid recomputing the more expensive things unless something really changed that invalidates the cached value. Originally this code was simply a standalone struct type, but since many of the properties make sense as style properties, I'm attempting to migrate this code to use style properties where possible - and the ability to simply add `#[derive(PartialEq, Eq, Hash)]` just inside the `prop_extractor!` invocation simplifies the implementation.
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Implements
Hash,PartialEqandEqonExtratorFieldwhereR::Typealso implements that trait, and enables theprop_extractor!macro to accept zero or more attributes preceding the type definition.Rationale: Makes implementing these traits as simple as it would be in an ordinary
structdeclaration.Use-case: In my particular case, I have some expensive-to-recompute bezier paths which are computed once in my
View'slayoutfunction; and some relatively trivial to recompute coordinates that change more often, and indicator which points to some position on those paths. By keeping a hash of those properties that could require recomputation of the path (line size, component size, things like that) I can avoid recomputing the more expensive things unless something really changed that invalidates the cached value.Originally this code was simply a standalone struct type, but since many of the properties make sense as style properties, I'm attempting to migrate this code to use style properties where possible - and the ability to simply add
#[derive(PartialEq, Eq, Hash)]just inside theprop_extractor!invocation simplifies the implementation.