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Inspired by [queron query](https://github.com/FerionVE/guion/blob/master/src/queron/query.rs) and Rust's upcoming [Provider API](rust-lang/rust#96024). It uses a query type with GAT response type to allow downcasting and responding with non-'static types for e.g. traitcasting.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,88 +1,107 @@ | ||
| //! Macros for implementing traitcast for widgets | ||
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| use std::any::TypeId; | ||
| use std::marker::PhantomData; | ||
| use std::ptr::NonNull; | ||
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| use crate::env::Env; | ||
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| pub mod widget; | ||
| pub mod handler; | ||
| pub trait WQuery<E>: 'static { | ||
| type Result<'a>: Sized + 'a; | ||
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| // TODO use ptr_metadata | ||
| //fn covariant<'a,'s>(v: Self::Result<'a>) -> Self::Result<'s> where 'a: 's; | ||
| } | ||
| pub trait WQueryGeneric<E>: 'static { | ||
| type Result<'a,G>: Sized + 'a where G: ?Sized + 'a; | ||
| } | ||
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| /// U N S O U N D | ||
| #[repr(C)] | ||
| #[derive(Copy, Clone)] | ||
| #[doc(hidden)] | ||
| pub struct TraitObject { | ||
| data: *mut (), | ||
| vtable: *mut (), | ||
| pub struct WQueryResponder<'s,'a,E> where 'a: 's { | ||
| type_id: TypeId, // T | ||
| response: NonNull<()>, // &'s mut Option<T::Result<'a>> | ||
| _p: PhantomData<(&'s mut &'a mut (),E)>, // invariant 'a | ||
| } | ||
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| const _: () = assert!(std::mem::size_of::<TraitObject>() == std::mem::size_of::<&dyn std::any::Any>()); | ||
| const _: () = assert!(std::mem::align_of::<TraitObject>() == std::mem::align_of::<&dyn std::any::Any>()); | ||
| impl<'a,E> WQueryResponder<'_,'a,E> where E: Env { | ||
| #[inline] | ||
| pub fn new<T>(respond_into: &mut Option<T::Result<'a>>) -> Self where T: WQuery<E> + ?Sized { | ||
| Self { | ||
| type_id: TypeId::of::<T>(), | ||
| response: NonNull::<Option<T::Result<'a>>>::from(respond_into).cast::<()>(), | ||
| _p: PhantomData, | ||
| } | ||
| } | ||
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| #[inline] | ||
| pub fn try_respond<T>(&mut self, respond: impl FnOnce() -> T::Result<'a>) -> bool where T: WQuery<E> + ?Sized { | ||
| self.try_downcast::<T>().map(#[inline] |v| *v = Some(respond()) ).is_some() | ||
| } | ||
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| #[inline] | ||
| pub fn try_respond_2<T>(&mut self, respond: impl FnOnce(&mut Option<T::Result<'a>>)) -> bool where T: WQuery<E> + ?Sized { | ||
| self.try_downcast::<T>().map(respond).is_some() | ||
| } | ||
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| /// This macro is used inside [`Widget/WidgetMut`](Widget) impls | ||
| /// | ||
| /// Example: | ||
| /// ```ignore | ||
| /// impl_traitcast!( | ||
| /// dyn IButton => |s| s; | ||
| /// dyn IButtonState => |s| &s.state; | ||
| /// ); | ||
| /// | ||
| #[macro_export] | ||
| macro_rules! impl_traitcast { | ||
| ($srcor:ty: $($trait:ty => |$id:ident| $access:expr; )*) => { | ||
| #[inline] | ||
| unsafe fn _as_trait_ref<'impl_traitcast_lt_a>(&'impl_traitcast_lt_a self, t: std::any::TypeId) -> Option<$crate::traitcast::TraitObject> { | ||
| $( | ||
| if t == std::any::TypeId::of::<<($srcor) as $crate::traitcast::TraitcastImpl::<'_,$trait>>::DestTypeID>() { | ||
| let $id = self; | ||
| let s: &'impl_traitcast_lt_a $trait = $access; | ||
| let s = std::mem::transmute::<&'impl_traitcast_lt_a $trait,$crate::traitcast::TraitObject>(s); | ||
| return Some(s); | ||
| } | ||
| );* | ||
| /// non zero cost respond ops should be extracted into a fn/closure or use try_respond, so that this part can be inlined. | ||
| #[inline] | ||
| pub fn try_downcast<'s,T>(&'s mut self) -> Option<&'s mut Option<T::Result<'a>>> where 'a: 's, T: WQuery<E> + ?Sized { | ||
| if TypeId::of::<T>() == self.type_id { | ||
| Some(unsafe { | ||
| self.response.cast::<Option<T::Result<'a>>>().as_mut() | ||
| }) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
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| #[inline] | ||
| pub fn fork(&mut self) -> WQueryResponder<'_,'a,E> { | ||
| WQueryResponder { | ||
| type_id: self.type_id, | ||
| response: self.response, | ||
| _p: PhantomData, | ||
| } | ||
| } | ||
| } | ||
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| #[doc(hidden)] | ||
| pub trait TraitcastImplBase<'a> { | ||
| unsafe fn _as_trait_ref(&self, t: TypeId) -> Option<TraitObject>; | ||
| pub struct WQueryResponderGeneric<'s,'a,Q,G,E> where 'a: 's, Q: WQueryGeneric<E> + ?Sized, G: ?Sized + 'a { | ||
| response: &'s mut Option<Q::Result<'a,G>>, | ||
| _p: PhantomData<(&'s mut &'a mut G,&'s mut Q,E)>, // invariant 'a | ||
| } | ||
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| /// Trait to secure Traitcasting, generally implemented by [macro](traitcast_for) | ||
| /// - Always implemented on `dyn WidgetDyn<E>` or `dyn Handler<E>` | ||
| /// - `T` is the destination `dyn Trait` to which should be traitcasted | ||
| /// - `DestTypeID` must be the same type as `T`, but with 'static lifetimes. Used to retrieve TypeID | ||
| #[doc(hidden)] | ||
| pub unsafe trait TraitcastImpl<'a,T>: TraitcastImplBase<'a> where T: ?Sized { | ||
| type DestTypeID: ?Sized + 'static; | ||
| impl<'a,'sa,Q,G,E> WQueryResponderGeneric<'sa,'a,Q,G,E> where E: Env, Q: WQueryGeneric<E> + ?Sized, G: ?Sized { | ||
| #[inline] | ||
| pub fn new(respond_into: &'sa mut Option<Q::Result<'a,G>>) -> Self { | ||
| Self { | ||
| response: respond_into, | ||
| _p: PhantomData, | ||
| } | ||
| } | ||
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| #[inline] | ||
| unsafe fn _try_traitcast_ref<'s>(senf: &'s Self) -> Result<&'s T,()> { | ||
| // god plz fix https://github.com/rust-lang/rust/issues/51826 | ||
| let t = TypeId::of::<Self::DestTypeID>(); | ||
| let t = senf._as_trait_ref(t); | ||
| if let Some(v) = t { | ||
| Ok(std::mem::transmute_copy::<TraitObject,&'s T>(&v)) | ||
| pub fn try_respond<T>(&mut self, fun: impl FnOnce() -> T::Result<'a,G>) -> bool where T: WQueryGeneric<E> + ?Sized { | ||
| self.try_downcast::<T>().map(#[inline] |v| *v = Some(fun()) ).is_some() | ||
| } | ||
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| #[inline] | ||
| pub fn try_respond_2<T>(&mut self, fun: impl FnOnce(&mut Option<T::Result<'a,G>>)) -> bool where T: WQueryGeneric<E> + ?Sized { | ||
| self.try_downcast::<T>().map(fun).is_some() | ||
| } | ||
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| #[inline] | ||
| pub fn try_downcast<'s,T>(&'s mut self) -> Option<&'s mut Option<T::Result<'a,G>>> where 'a: 's, T: WQueryGeneric<E> + ?Sized { | ||
| if TypeId::of::<T>() == TypeId::of::<Q>() { | ||
| Some(unsafe { | ||
| let resp: &'s mut Option<Q::Result<'a,G>> = self.response; | ||
| &mut *(resp as *mut _ as *mut Option<T::Result<'a,G>>) | ||
| }) | ||
| } else { | ||
| Err(()) | ||
| None | ||
| } | ||
| } | ||
| } | ||
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| /// Syntax: | ||
| /// `traitcast_for!([<...>] Trait[<...>] [where ...]);` | ||
| #[macro_export] | ||
| macro_rules! traitcast_for { | ||
| ( | ||
| $( < $($args:ident),* $(,)* > )? | ||
| $trait:path | ||
| $(where $($preds:tt)+)? | ||
| ) => { | ||
| unsafe impl<'w,TCO,$( $($args),* )?> $crate::traitcast::TraitcastImpl<'w,dyn $trait+'w> for TCO where TCO: $crate::traitcast::TraitcastImplBase<'w> + ?Sized, $($($preds)+ )? { | ||
| type DestTypeID = dyn $trait+'static; | ||
| #[inline] | ||
| pub fn fork(&mut self) -> WQueryResponderGeneric<'_,'a,Q,G,E> { | ||
| WQueryResponderGeneric { | ||
| response: self.response, | ||
| _p: PhantomData, | ||
| } | ||
| } | ||
| } |
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