ecs: implement an actual Filter trait, create a Changed filter

lyra-ecs/src/lib.rs

@@ -1,3 +1,5 @@
+#![feature(associated_type_defaults)]
+
 extern crate self as lyra_ecs;
 
 #[allow(unused_imports)]

lyra-ecs/src/query/filter/changed.rs

@@ -0,0 +1,97 @@
+use std::marker::PhantomData;
+
+use crate::{query::{AsFilter, AsQuery, Fetch, Filter, Query}, Component, ComponentColumn, DynTypeId, Tick, World};
+
+pub struct ChangedFetcher<'a, T> {
+    col: &'a ComponentColumn,
+    tick: Tick,
+    _phantom: PhantomData<&'a T>,
+}
+
+impl<'a, T> Fetch<'a> for ChangedFetcher<'a, T>
+where
+    T: 'a,
+{
+    type Item = bool;
+
+    fn dangling() -> Self {
+        unreachable!()
+    }
+
+    unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
+        let tick = self.col.entity_ticks[entity.0 as usize];
+        tick >= self.tick
+    }
+}
+
+/// A filter that fetches components that have changed.
+/// 
+/// Since [`AsQuery`] is implemented for `&T`, you can use this query like this:
+/// ```nobuild
+/// for ts in world.view::<&T>() {
+///     println!("Got a &T!");
+/// }
+/// ```
+pub struct Changed<T> {
+    type_id: DynTypeId,
+    _phantom: PhantomData<T>
+}
+
+impl<T: Component> Default for Changed<T> {
+    fn default() -> Self {
+        Self {
+            type_id: DynTypeId::of::<T>(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+// manually implemented to avoid a Copy bound on T
+impl<T> Copy for Changed<T> {}
+
+// manually implemented to avoid a Clone bound on T
+impl<T> Clone for Changed<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: Component> Changed<T> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl<T: Component> Query for Changed<T>
+where
+    T: 'static
+{
+    type Item<'a> = bool;
+    type Fetch<'a> = ChangedFetcher<'a, T>;
+
+    fn new() -> Self {
+        Changed::<T>::new()
+    }
+
+    fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
+        archetype.has_column(self.type_id)
+    }
+
+    unsafe fn fetch<'a>(&self, w: &'a World, a: &'a crate::archetype::Archetype, _: crate::Tick) -> Self::Fetch<'a> {
+        ChangedFetcher {
+            col: a.get_column(self.type_id).unwrap(),
+            tick: w.current_tick(),
+            _phantom: PhantomData::<&T>,
+        }
+    }
+}
+
+impl<T: Component> AsQuery for Changed<T> {
+    type Query = Self;
+}
+
+impl<'a, T: Component> Filter for Changed<T> { }
+
+impl<T: Component> AsFilter for Changed<T> {
+    type Filter = Self;
+}

lyra-ecs/src/query/filter/mod.rs

@@ -6,3 +6,6 @@ pub use or::*;
 
 mod not;
 pub use not::*;
+
+mod changed;
+pub use changed::*;

lyra-ecs/src/query/mod.rs

@@ -89,6 +89,12 @@ pub trait AsQuery {
     type Query: Query;
 }
 
+/// A trait for getting the filter of a type.
+pub trait AsFilter {
+    /// The query for this type
+    type Filter: Filter;
+}
+
 pub trait IntoQuery {
     fn into_query(self) -> Self;
 }
@@ -125,10 +131,22 @@ impl Query for () {
     }
 }
 
+impl Filter for () {
+    type Item<'a> = bool;
+}
+
 impl AsQuery for () {
     type Query = ();
 }
 
+pub trait Filter: Query {
+    type Item<'a> = bool;
+}
+
+impl AsFilter for () {
+    type Filter = ();
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{World, archetype::Archetype, tests::Vec2};

lyra-ecs/src/query/tuple.rs

@@ -1,8 +1,8 @@
 use crate::World;
 
-use super::{Query, Fetch, AsQuery};
+use super::{Query, Fetch, AsQuery, Filter, AsFilter};
 
-impl<'a, F1> Fetch<'a> for (F1,)
+/* impl<'a, F1> Fetch<'a> for (F1,)
 where
     F1: Fetch<'a>,
 {
@@ -102,7 +102,7 @@ where
     Q2: AsQuery,
 {
     type Query = (Q1::Query, Q2::Query);
-}
+} */
 
 macro_rules! impl_bundle_tuple {
     ( $($name: ident),+ ) => (
@@ -154,10 +154,39 @@ macro_rules! impl_bundle_tuple {
         impl<$($name: AsQuery),+> AsQuery for ($($name,)+) {
             type Query = ($($name::Query,)+);
         }
+
+        #[allow(non_snake_case)]
+        impl<$($name: Filter),+> Filter for ($($name,)+) {
+            //type Item<'a> = ($(<$name as Query>::Item<'a>,)+);
+            //type Fetch<'a> = ($(<$name as Query>::Fetch<'a>,)+);
+
+            /* fn new() -> Self {
+                ( $($name::new(),)+ )
+            }
+
+            fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
+                let ( $($name,)+ ) = self;
+
+                // this is the only way I could figure out how to do an 'and'
+                let bools = vec![$($name.can_visit_archetype(archetype),)+];
+                bools.iter().all(|b| *b)
+            }
+
+            unsafe fn fetch<'a>(&self, world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
+                let ( $($name,)+ ) = self;
+                ( $($name.fetch(world, archetype, tick),)+ )
+            } */
+        }
+
+        impl<$($name: AsFilter),+> AsFilter for ($($name,)+) {
+            type Filter = ($($name::Filter,)+);
+        }
     );
 }
 
 // Hopefully up to 16 queries in a SINGLE view is enough
+impl_bundle_tuple! { Q1 }
+impl_bundle_tuple! { Q1, Q2 }
 impl_bundle_tuple! { Q1, Q2, Q3 }
 impl_bundle_tuple! { Q1, Q2, Q3, Q4 }
 impl_bundle_tuple! { Q1, Q2, Q3, Q4, Q5 }

lyra-ecs/src/query/view.rs

@@ -2,11 +2,11 @@ use std::ops::Range;
 
 use crate::{archetype::Archetype, world::{ArchetypeEntityId, World}, EntityId, Tick};
 
-use super::{Query, Fetch, AsQuery};
+use super::{AsFilter, AsQuery, Fetch, Filter, Query};
 
 pub type View<'a, Q, F = ()> = ViewState<'a, <Q as AsQuery>::Query, <F as AsQuery>::Query>;
 
-pub struct ViewState<'a, Q: Query, F: Query> {
+pub struct ViewState<'a, Q: Query, F: Filter> {
     world: &'a World,
     query: Q,
     filter: F,
@@ -16,7 +16,7 @@ pub struct ViewState<'a, Q: Query, F: Query> {
 impl<'a, Q, F> ViewState<'a, Q, F>
 where
     Q: Query,
-    F: Query,
+    F: Filter,
 {
     pub fn new(world: &'a World, query: Q, filter: F, archetypes: Vec<&'a Archetype>) -> Self {
         Self {
@@ -38,7 +38,7 @@ where
     }
 
     /// Consumes `self`, adding a filter to the view.
-    pub fn with<U: AsQuery>(self, filter: U::Query) -> ViewState<'a, Q, (F, U::Query)> {
+    pub fn with<U: AsFilter>(self, filter: U::Filter) -> ViewState<'a, Q, (F, U::Filter)> {
         ViewState::new(self.world, self.query, (self.filter, filter), self.archetypes)
     }
 }
@@ -46,18 +46,19 @@ where
 impl<'a, Q, F> IntoIterator for ViewState<'a, Q, F>
 where
     Q: Query,
-    F: Query,
+    F: Filter,
 {
     type Item = Q::Item<'a>;
 
     type IntoIter = ViewIter<'a, Q, F>;
 
     fn into_iter(self) -> Self::IntoIter {
-        let tick = self.world.tick_tracker().tick_when(Q::MUTATES);
+        //let tick = self.world.tick_tracker().tick_when(Q::MUTATES);
 
         ViewIter {
             world: self.world,
-            tick,
+            tick: self.world.current_tick(),
+            has_ticked: false,
             query: self.query,
             filter: self.filter,
             fetcher: None,
@@ -69,9 +70,10 @@ where
     }
 }
 
-pub struct ViewIter<'a, Q: Query, F: Query> {
+pub struct ViewIter<'a, Q: Query, F: Filter> {
     world: &'a World,
     tick: Tick,
+    has_ticked: bool,
     query: Q,
     filter: F,
     fetcher: Option<Q::Fetch<'a>>,
@@ -84,7 +86,7 @@ pub struct ViewIter<'a, Q: Query, F: Query> {
 impl<'a, Q, F> Iterator for ViewIter<'a, Q, F>
 where
     Q: Query,
-    F: Query,
+    F: Filter,
 {
     type Item = Q::Item<'a>;
 
@@ -110,6 +112,13 @@ where
                 let entity_index = ArchetypeEntityId(entity_index);
 
                 if fetcher.can_visit_item(entity_index) && filter_fetcher.can_visit_item(entity_index) {
+                    // only tick the world if the filter has fetched, and when the world hasn't
+                    // been ticked yet.
+                    if Q::MUTATES && !self.has_ticked {
+                        self.has_ticked = true;
+                        self.tick = self.world.tick();
+                    }
+
                     let i = unsafe { fetcher.get_item(entity_index) };
                     return Some(i);
                 }
@@ -147,17 +156,17 @@ pub struct ViewOne<'a, Q: Query> {
 
 impl<'a, Q: Query> ViewOne<'a, Q> {
     pub fn new(world: &'a World, entity: EntityId, query: Q) -> Self {
-        let tick = world.tick_tracker().tick_when(Q::MUTATES);
+        //let tick = world.tick_tracker().tick_when(Q::MUTATES);
 
         Self {
             world,
-            tick,
+            tick: world.current_tick(),
             entity,
             query
         }
     }
 
-    pub fn get(&self) -> Option<Q::Item<'a>> {
+    pub fn get(self) -> Option<Q::Item<'a>> {
         if let Some(record) = self.world.entities.arch_index.get(&self.entity) {
             let arch = self.world.archetypes.get(&record.id)
                 .expect("An invalid record was specified for an entity");
@@ -165,6 +174,9 @@ impl<'a, Q: Query> ViewOne<'a, Q> {
             if self.query.can_visit_archetype(arch) {
                 let mut fetch = unsafe { self.query.fetch(self.world, arch, self.tick) };
                 if fetch.can_visit_item(record.index) {
+                    // only tick the world when something is actually fetched.
+                    self.world.tick();
+
                     return Some(unsafe { fetch.get_item(record.index) });
                 }
             }

lyra-ecs/src/relation/mod.rs

@@ -2,6 +2,7 @@ use std::marker::PhantomData;
 
 use lyra_ecs_derive::Component;
 
+use crate::query::Filter;
 use crate::query::Query;
 use crate::query::ViewState;
 use crate::Entity;
@@ -98,7 +99,7 @@ impl World {
 impl<'a, Q, F> ViewState<'a, Q, F>
 where
     Q: Query,
-    F: Query,
+    F: Filter,
 {
     /// Consumes `self` to return a view that fetches the relation to a specific target entity.
     pub fn relates_to<R>(self, target: Entity) -> ViewState<'a, (Q, QueryRelatesTo<R>), F>

lyra-ecs/src/system/fn_sys.rs

@@ -1,7 +1,7 @@
 use std::{any::Any, marker::PhantomData, ptr::NonNull};
 
 use paste::paste;
-use crate::{World, Access, ResourceObject, query::{Query, ViewState, ResMut, Res}};
+use crate::{World, Access, ResourceObject, query::{Query, Filter, ViewState, ResMut, Res}};
 
 use super::{System, IntoSystem};
 
@@ -140,7 +140,7 @@ impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N, O, P }
 impl<'c, Q, F> FnArgFetcher for ViewState<'c, Q, F>
 where
     Q: Query + 'static,
-    F: Query + 'static,
+    F: Filter + 'static,
 {
     type State = (Q, F);
     type Arg<'a, 'state> = ViewState<'a, Q, F>;

lyra-ecs/src/world.rs

@@ -2,7 +2,7 @@ use std::{any::TypeId, collections::HashMap, ptr::NonNull};
 
 use atomic_refcell::{AtomicRef, AtomicRefMut};
 
-use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsQuery, Query, ViewIter, ViewOne, ViewState}, resource::ResourceData, ComponentInfo, DynTypeId, DynamicBundle, Entities, Entity, ResourceObject, Tick, TickTracker};
+use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsFilter, AsQuery, Query, ViewIter, ViewOne, ViewState}, resource::ResourceData, ComponentInfo, DynTypeId, DynamicBundle, Entities, Entity, ResourceObject, Tick, TickTracker};
 
 /// The id of the entity for the Archetype.
 /// 
@@ -347,9 +347,9 @@ impl World {
     }
 
     /// View into the world for a set of entities that satisfy the query and the filter.
-    pub fn filtered_view<Q: AsQuery, F: AsQuery>(&self) -> ViewState<Q::Query, F::Query> {
+    pub fn filtered_view<Q: AsQuery, F: AsFilter>(&self) -> ViewState<Q::Query, F::Filter> {
         let archetypes = self.archetypes.values().collect();
-        ViewState::<Q::Query, F::Query>::new(self, Q::Query::new(), F::Query::new(), archetypes)
+        ViewState::<Q::Query, F::Filter>::new(self, Q::Query::new(), F::Filter::new(), archetypes)
     }
 
     /// View into the world for a set of entities that satisfy the queries.
@@ -360,9 +360,9 @@ impl World {
     }
 
     /// View into the world for a set of entities that satisfy the queries.
-    pub fn filtered_view_iter<Q: AsQuery, F: AsQuery>(&self) -> ViewIter<Q::Query, F::Query> {
+    pub fn filtered_view_iter<Q: AsQuery, F: AsFilter>(&self) -> ViewIter<Q::Query, F::Filter> {
         let archetypes = self.archetypes.values().collect();
-        let v = ViewState::new(self, Q::Query::new(), F::Query::new(), archetypes);
+        let v = ViewState::new(self, Q::Query::new(), F::Filter::new(), archetypes);
         v.into_iter()
     }