lua: implement Changed query that supports components and resources

examples/lua-scripting/scripts/test.lua

@@ -90,15 +90,19 @@ function on_update()
         end
     end, Transform) ]]
 
+    -- although WorldTransform isn't used, I only want to modify entities with that component.
     local view = View.new(Transform, WorldTransform, Res(DeltaTime))
     local res = world:view_query(view)
-
-    for entity, transform, world_tran, dt in res:iter() do
-        print("Entity is at: " .. tostring(world_tran))
-
+    for entity, transform, _wt, dt in res:iter() do
         transform:translate(0, 0.15 * dt, 0)
         entity:update(transform)
     end
+
+    local changed_view = View.new(Changed(Transform))
+    local changed_res = world:view_query(changed_view)
+    for _, transform in changed_res:iter() do
+        print("Entity transform changed to: " .. tostring(transform))
+    end
 end
 
 --[[ function on_post_update()

lyra-ecs/src/archetype.rs

@@ -214,16 +214,34 @@ impl ComponentColumn {
         moved_index
     }
 
-    /// Get the pointer of the component for the entity.
+    /// Get the pointer of the component for an entity.
     ///
     /// It is assumed that the component will be mutated, meaning the component's tick will be
     /// updated.
-    pub fn get_entity_ptr(&mut self, entity_index: usize, tick: &Tick) -> NonNull<u8> {
-        self.entity_ticks.insert(entity_index, *tick);
+    pub fn component_ptr(&mut self, entity_index: usize, tick: &Tick) -> NonNull<u8> {
+        self.entity_ticks[entity_index] = *tick;
         let size = self.info.layout().size();
         unsafe { NonNull::new_unchecked(self.borrow_ptr().as_ptr().add(entity_index * size)) }
     }
 
+    /// Get the pointer of the component for an entity without ticking.
+    /// 
+    /// Since this does not tick, only use this if you know the pointer will not be mutated.
+    pub fn component_ptr_non_tick(&self, entity_index: usize) -> NonNull<u8> {
+        let size = self.info.layout().size();
+        unsafe { NonNull::new_unchecked(self.borrow_ptr().as_ptr().add(entity_index * size)) }
+    }
+
+    /// Get the tick of a component for an entity.
+    pub fn component_tick(&self, entity_index: usize) -> Option<Tick> {
+        self.entity_ticks.get(entity_index).cloned()
+    }
+
+    pub fn component_has_changed(&self, entity_index: usize, world_tick: Tick) -> Option<bool> {
+        self.component_tick(entity_index)
+            .map(|tick| *tick >= *world_tick - 1)
+    }
+
     pub fn borrow_ptr(&self) -> Ref<NonNull<u8>> {
         self.data.borrow()
     }
@@ -272,7 +290,7 @@ pub struct Archetype {
     /// Can be used to map `ArchetypeEntityId` to an Entity since `ArchetypeEntityId` has
     /// the index that the entity is stored at.
     pub(crate) entities: Vec<Entity>,
-    pub(crate) columns: Vec<ComponentColumn>,
+    pub columns: Vec<ComponentColumn>,
     capacity: usize,
 }
 

lyra-ecs/src/entity.rs

@@ -77,4 +77,4 @@ impl Entities {
     pub(crate) fn insert_entity_record(&mut self, entity: Entity, record: Record) {
         self.arch_index.insert(entity.id, record);
     }
-}
+}

lyra-ecs/src/query/dynamic/view.rs

@@ -24,6 +24,10 @@ impl DynamicViewState {
         }
     }
 
+    pub fn queries_num(&self) -> usize {
+        self.queries.len()
+    }
+
     pub fn push(&mut self, dyn_query: QueryDynamicType) {
         self.queries.push(dyn_query);
     }

lyra-ecs/src/query/resource.rs

@@ -112,7 +112,7 @@ impl<'a, T: ResourceObject> Res<'a, T> {
 
     /// Returns a boolean indicating if the resource changed.
     pub fn changed(&self) -> bool {
-        *self.inner.tick - 1 >= *self.world_tick - 1
+        *self.inner.tick >= *self.world_tick - 1
     }
 
     /// The tick that this resource was last modified at

lyra-ecs/src/world.rs

@@ -26,11 +26,11 @@ pub struct Record {
 
 #[derive(Clone)]
 pub struct World {
-    pub(crate) archetypes: HashMap<ArchetypeId, Archetype>,
+    pub archetypes: HashMap<ArchetypeId, Archetype>,
     next_archetype_id: ArchetypeId,
     resources: HashMap<TypeId, ResourceData>,
     tracker: TickTracker,
-    pub(crate) entities: Entities,
+    pub entities: Entities,
 }
 
 impl Default for World {
@@ -467,6 +467,13 @@ impl World {
         })
     }
 
+    /// Get the tick of a resource.
+    /// 
+    /// This tick represents the last time the resource was mutated.
+    pub fn get_resource_tick<T: ResourceObject>(&self) -> Option<Tick> {
+        self.get_tracked_resource::<T>().map(|r| r.tick)
+    }
+
     /// Gets a reference to a change tracked resource.
     /// 
     /// You will have to manually downcast the inner resource. Most people don't need this, see

lyra-reflect/src/component.rs

@@ -1,6 +1,6 @@
 use std::{any::{Any, TypeId}, cell::{Ref, RefMut}};
 
-use lyra_ecs::{Component, ComponentInfo, World, Entity, DynamicBundle};
+use lyra_ecs::{query::{filter::Changed, TickOf}, Component, ComponentInfo, DynamicBundle, Entity, Tick, World};
 
 use crate::{Reflect, FromType};
 
@@ -18,6 +18,8 @@ pub struct ReflectedComponent {
     fn_bundle_insert: for<'a> fn (dynamic_bundle: &'a mut DynamicBundle, component: Box<dyn Reflect>),
     fn_reflect: for<'a> fn (world: &'a World, entity: Entity) -> Option<Ref<'a, dyn Reflect>>,
     fn_reflect_mut: for<'a> fn (world: &'a mut World, entity: Entity) -> Option<RefMut<'a, dyn Reflect>>,
+    fn_reflect_tick: for<'a> fn (world: &'a World, entity: Entity) -> Option<Tick>,
+    fn_reflect_is_changed: for<'a> fn (world: &'a World, entity: Entity) -> Option<bool>,
 }
 
 impl ReflectedComponent {
@@ -40,6 +42,14 @@ impl ReflectedComponent {
     pub fn reflect_mut<'a>(&'a mut self, world: &'a mut World, entity: Entity) -> Option<RefMut<'a, dyn Reflect>> {
         (self.fn_reflect_mut)(world, entity)
     }
+
+    pub fn reflect_tick<'a>(&'a self, world: &'a World, entity: Entity) -> Option<Tick> {
+        (self.fn_reflect_tick)(world, entity)
+    }
+
+    pub fn reflect_is_changed<'a>(&'a self, world: &'a World, entity: Entity) -> Option<bool> {
+        (self.fn_reflect_is_changed)(world, entity)
+    }
 }
 
 impl<C: Component + Reflect> FromType<C> for ReflectedComponent {
@@ -69,6 +79,12 @@ impl<C: Component + Reflect> FromType<C> for ReflectedComponent {
                 world.view_one::<&mut C>(entity)
                     .get().map(|c| c as RefMut<dyn Reflect>)
             },
+            fn_reflect_tick: |world: &World, entity: Entity| {
+                world.view_one::<TickOf<C>>(entity).get()
+            },
+            fn_reflect_is_changed: |world: &World, entity: Entity| {
+                world.view_one::<Changed<C>>(entity).get()
+            }
         }
     }
 }

lyra-reflect/src/resource.rs

@@ -1,6 +1,6 @@
 use std::{any::{Any, TypeId}, ptr::NonNull};
 
-use lyra_ecs::{AtomicRef, AtomicRefMut, ResourceObject, World};
+use lyra_ecs::{AtomicRef, AtomicRefMut, ResourceObject, Tick, World};
 
 use crate::{Reflect, FromType};
 
@@ -9,6 +9,8 @@ pub struct ReflectedResource {
     pub type_id: TypeId,
 
     fn_reflect: for<'a> fn (world: &'a World) -> Option<AtomicRef<'a, dyn Reflect>>,
+    fn_reflect_tick: for<'a> fn (world: &'a World) -> Option<Tick>,
+    fn_reflect_is_changed: fn (world: &World) -> Option<bool>,
     fn_reflect_mut: for<'a> fn (world: &'a mut World) -> Option<AtomicRefMut<'a, dyn Reflect>>,
     fn_reflect_ptr: fn (world: &mut World) -> Option<NonNull<u8>>,
     fn_refl_insert: fn (world: &mut World, this: Box<dyn Reflect>),
@@ -20,6 +22,14 @@ impl ReflectedResource {
         (self.fn_reflect)(world)
     }
 
+    pub fn reflect_tick(&self, world: &World) -> Option<Tick> {
+        (self.fn_reflect_tick)(world)
+    }
+
+    pub fn reflect_is_changed(&self, world: &World) -> Option<bool> {
+        (self.fn_reflect_is_changed)(world)
+    }
+
     /// Retrieves a mutable reflected resource from the world.
     pub fn reflect_mut<'a>(&self, world: &'a mut World) -> Option<AtomicRefMut<'a, dyn Reflect>> {
         (self.fn_reflect_mut)(world)
@@ -47,6 +57,13 @@ impl<T: ResourceObject + Reflect> FromType<T> for ReflectedResource {
                         AtomicRef::map(r, |r| r as &dyn Reflect)
                     })
             },
+            fn_reflect_tick: |world: &World| {
+                world.get_resource_tick::<T>()
+            },
+            fn_reflect_is_changed: |world: &World| {
+                world.get_resource::<T>()
+                    .map(|r| r.changed())
+            },
             fn_reflect_mut: |world: &mut World| {
                 world.get_resource_mut::<T>()
                     .map(|r| {

lyra-scripting/scripts/lua/ecs.lua

@@ -3,4 +3,11 @@
 ---@return ResQuery
 function Res(resource)
     return ResQuery.new(resource)
+end
+
+---Create a Changed Query of a resource or component.
+---@param resource table|userdata
+---@return ChangedQuery
+function Changed(val)
+    return ChangedQuery.new(val)
 end

lyra-scripting/src/lua/dynamic_iter.rs

@@ -57,15 +57,13 @@ fn next_lua(lua: &mlua::Lua, world: &lyra_ecs::World, dyn_view: &mut DynamicView
         let mut dynamic_row = vec![];
         for d in row.iter() {
             let id = d.info.type_id().as_rust();
-            /* let reflected_components = 
-                unsafe { reflected_components.as_ref().unwrap().as_ref() }; */
             
             let reg_type = reflected_components.get_type(id)
                 .expect("Requested type was not found in TypeRegistry");
             let proxy = reg_type.get_data::<ReflectLuaProxy>()
                 // TODO: properly handle this error
                 .expect("Type does not have ReflectLuaProxy as a TypeData");
-            let value = (proxy.fn_as_lua)(lua, d.ptr.cast()).unwrap()
+            let value = proxy.as_lua(lua, d.ptr.cast()).unwrap()
                 .into_lua(lua).unwrap();
 
             dynamic_row.push(ReflectedItem {

lyra-scripting/src/lua/ecs/query/changed.rs

@@ -0,0 +1,98 @@
+use lyra_reflect::{ReflectWorldExt, RegisteredType, TypeRegistry};
+use mlua::IntoLua;
+
+use crate::{
+    lua::{LuaComponent, ReflectLuaProxy, FN_NAME_INTERNAL_ECS_QUERY_RESULT},
+    ReflectBranch, ScriptEntity, ScriptWorldPtr,
+};
+
+#[derive(Clone)]
+pub struct LuaChangedQuery(LuaComponent);
+
+impl mlua::FromLua for LuaChangedQuery {
+    fn from_lua(value: mlua::Value, _: &mlua::Lua) -> mlua::Result<Self> {
+        let tyname = value.type_name();
+        value
+            .as_userdata()
+            .ok_or(mlua::Error::FromLuaConversionError {
+                from: tyname,
+                to: "ChangedQuery".into(),
+                message: None,
+            })
+            .and_then(|ud| ud.borrow::<Self>())
+            .map(|ud| ud.clone())
+    }
+}
+
+impl mlua::UserData for LuaChangedQuery {
+    fn add_methods<M: mlua::UserDataMethods<Self>>(methods: &mut M) {
+        methods.add_function("new", |_, comp: LuaComponent| Ok(Self(comp)));
+
+        methods.add_method(
+            FN_NAME_INTERNAL_ECS_QUERY_RESULT,
+            |lua, this, (world, en): (ScriptWorldPtr, ScriptEntity)| {
+                let mut world = world.write();
+                let reflect = this.0.reflect_type()?;
+
+                let tyid = reflect.reflect_branch.reflect_type_id();
+                match &reflect.reflect_branch {
+                    ReflectBranch::Component(comp) => {
+                        if !comp.reflect_is_changed(&world, *en).unwrap_or(false) {
+                            return Ok(mlua::Value::Boolean(false));
+                        }
+
+                        // get the pointer of the component in the archetype column.
+                        let arch = world.entity_archetype(*en).unwrap();
+                        let arch_idx = *arch.entity_indexes().get(&en).unwrap();
+
+                        let col = match arch.get_column(tyid) {
+                            Some(col) => col,
+                            None => {
+                                // the entity doesn't have the component
+                                return Ok(mlua::Value::Boolean(false));
+                            }
+                        };
+
+                        let col_ptr = col.component_ptr_non_tick(*arch_idx as usize).cast();
+
+                        // get the type registry to apply the new value
+                        let reg = world.get_resource::<TypeRegistry>().unwrap();
+                        let reg_type = reg.get_type(tyid).unwrap();
+
+                        let proxy = reg_type
+                            .get_data::<ReflectLuaProxy>()
+                            // this should actually be safe since the ReflectedIterator
+                            // attempts to get the type data before it is tried here
+                            .expect("Type does not have ReflectLuaProxy as a TypeData");
+                        proxy.as_lua(lua, col_ptr)
+                    }
+                    ReflectBranch::Resource(res) => {
+                        // Check if the resource was changed. Per API spec, must return false.
+                        match res.reflect_is_changed(&world) {
+                            Some(false) => {
+                                return Ok(mlua::Value::Boolean(false));
+                            }
+                            None => {
+                                // the resource was not found
+                                return Ok(mlua::Value::Nil);
+                            }
+                            _ => {}
+                        }
+
+                        // unwrap is safe here since the match above would verify that the
+                        // resource exists.
+                        let res_ptr = res.reflect_ptr(&mut world).unwrap();
+                        let reg_type = world
+                            .get_type::<RegisteredType>(tyid)
+                            .expect("Resource is not type registered!");
+                        let proxy = reg_type
+                            .get_data::<ReflectLuaProxy>()
+                            .expect("Type does not have ReflectLuaProxy as a TypeData");
+
+                        proxy.as_lua(lua, res_ptr.cast()).and_then(|ud| ud.into_lua(lua))
+                    }
+                }
+            },
+        );
+    }
+}

lyra-scripting/src/lua/ecs/query/mod.rs

@@ -1,25 +1,40 @@
 mod res;
 pub use res::*;
 
-use crate::{lua::{LuaComponent, FN_NAME_INTERNAL_ECS_QUERY_RESULT}, ScriptWorldPtr};
+mod changed;
+pub use changed::*;
+
+use lyra_ecs::Entity;
+
+use crate::{lua::{LuaComponent, FN_NAME_INTERNAL_ECS_QUERY_RESULT}, ScriptEntity, ScriptWorldPtr};
 
 #[derive(Clone)]
-pub struct LuaQuery {
-    query: LuaComponent
+enum QueryInner {
+    Component(LuaComponent),
+    Function(mlua::Function)
 }
 
+#[derive(Clone)]
+pub struct LuaQuery(QueryInner);
+
 impl LuaQuery {
     pub fn new(query: LuaComponent) -> Self {
-        Self {
-            query
-        }
+        Self(QueryInner::Component(query))
+    }
+
+    pub fn from_function(f: mlua::Function) -> Self {
+        Self(QueryInner::Function(f))
     }
 
     /// Get the result of the query
     /// 
     /// > WARNING: ensure that the world pointer is not locked. If its locked when you call this,
     /// you WILL cause a deadlock.
-    pub fn get_query_result(&self, world: ScriptWorldPtr) -> mlua::Result<mlua::Value> {
-        self.query.call_method(FN_NAME_INTERNAL_ECS_QUERY_RESULT, world)
+    pub fn get_query_result(&self, world: ScriptWorldPtr, entity: Entity) -> mlua::Result<mlua::Value> {
+        let lua_en = ScriptEntity(entity);
+        match &self.0 {
+            QueryInner::Component(comp) => comp.call_method(FN_NAME_INTERNAL_ECS_QUERY_RESULT, (world, lua_en)),
+            QueryInner::Function(function) => function.call((world, lua_en)),
+        }
     }
 }

lyra-scripting/src/lua/ecs/query/res.rs

@@ -2,8 +2,7 @@ use lyra_reflect::{ReflectWorldExt, RegisteredType};
 use mlua::IntoLua;
 
 use crate::{
-    lua::{LuaComponent, ReflectLuaProxy, FN_NAME_INTERNAL_ECS_QUERY_RESULT},
-    ScriptWorldPtr,
+    lua::{LuaComponent, ReflectLuaProxy, FN_NAME_INTERNAL_ECS_QUERY_RESULT}, ScriptEntity, ScriptWorldPtr
 };
 
 #[derive(Clone)]
@@ -34,7 +33,7 @@ impl mlua::UserData for LuaResQuery {
             })
         });
 
-        methods.add_method(FN_NAME_INTERNAL_ECS_QUERY_RESULT, |lua, this, world: ScriptWorldPtr| {
+        methods.add_method(FN_NAME_INTERNAL_ECS_QUERY_RESULT, |lua, this, (world, _): (ScriptWorldPtr, ScriptEntity)| {
             let mut world = world.write();
             let reflect = this.ty.reflect_type()?;
 
@@ -47,7 +46,7 @@ impl mlua::UserData for LuaResQuery {
                     .get_data::<ReflectLuaProxy>()
                     .expect("Type does not have ReflectLuaProxy as a TypeData");
 
-                (proxy.fn_as_lua)(lua, res_ptr.cast()).and_then(|ud| ud.into_lua(lua))
+                proxy.as_lua(lua, res_ptr.cast()).and_then(|ud| ud.into_lua(lua))
             } else {
                 // if the resource is not found in the world, return nil
                 Ok(mlua::Value::Nil)

lyra-scripting/src/lua/ecs/view.rs

@@ -1,9 +1,19 @@
-use std::{ptr::NonNull, sync::Arc};
+use std::sync::Arc;
 
-use lyra_ecs::{query::dynamic::{DynamicViewState, QueryDynamicType}, Entity};
+use atomic_refcell::AtomicRefCell;
+use lyra_ecs::{
+    query::dynamic::{DynamicViewState, QueryDynamicType},
+    Entity,
+};
 use mlua::{IntoLua, IntoLuaMulti, ObjectLike};
 
-use crate::{lua::{LuaComponent, LuaEntityRef, ReflectedIteratorOwned, TypeLookup, WorldError, FN_NAME_INTERNAL_ECS_QUERY_RESULT, FN_NAME_INTERNAL_REFLECT_TYPE}, ScriptBorrow, ScriptWorldPtr};
+use crate::{
+    lua::{
+        LuaComponent, LuaEntityRef, ReflectedIteratorOwned, TypeLookup, WorldError,
+        FN_NAME_INTERNAL_ECS_QUERY_RESULT, FN_NAME_INTERNAL_REFLECT_TYPE,
+    },
+    ScriptBorrow, ScriptWorldPtr,
+};
 
 use super::query::LuaQuery;
 
@@ -31,44 +41,37 @@ impl mlua::FromLua for ViewQueryItem {
 }
 
 impl ViewQueryItem {
-    pub fn is_filter(&self) -> bool {
-        // TODO: check if UserData is a rust implemented filter
-        matches!(self, ViewQueryItem::Function(_))
-    }
-
     /// Returns `true` if the QueryItem has a function of `name`.
-    /// 
+    ///
     /// Returns `false` if self is a function.
     pub fn has_function(&self, name: &str) -> mlua::Result<bool> {
         match self {
-            Self::UserData(ud) => {
-                ud.get::<mlua::Value>(name).map(|v| !v.is_nil())
-            },
-            Self::Table(t) => {
-                t.contains_key(name)
-            },
+            Self::UserData(ud) => ud.get::<mlua::Value>(name).map(|v| !v.is_nil()),
+            Self::Table(t) => t.contains_key(name),
             Self::Function(_) => Ok(false),
         }
     }
 
+    /// Returns `true` if self is a Query.
+    /// 
+    /// If self is a function, it will return true. Else, it checks for a function with the
+    /// name of [`FN_NAME_INTERNAL_ECS_QUERY_RESULT`] on the table or userdata. If the function
+    /// is found, it returns true.
     pub fn is_query(&self) -> mlua::Result<bool> {
-        self.has_function(FN_NAME_INTERNAL_ECS_QUERY_RESULT)
+        Ok(matches!(self, ViewQueryItem::Function(_))
+            || self.has_function(FN_NAME_INTERNAL_ECS_QUERY_RESULT)?)
     }
 
-    /// Clone self into a [`LuaComponent`].
-    pub fn as_component(&self) -> Option<LuaComponent> {
+    /// Get self as a [`LuaQuery`].
+    ///
+    /// If self is a function, it assumes that it is a filter.
+    pub fn as_query(&self) -> LuaQuery {
         match self.clone() {
-            ViewQueryItem::UserData(ud) => Some(LuaComponent::UserData(ud)),
-            ViewQueryItem::Table(t) => Some(LuaComponent::Table(t)),
-            ViewQueryItem::Function(_) => None
+            ViewQueryItem::UserData(ud) => LuaQuery::new(LuaComponent::UserData(ud)),
+            ViewQueryItem::Table(t) => LuaQuery::new(LuaComponent::Table(t)),
+            ViewQueryItem::Function(function) => LuaQuery::from_function(function),
         }
     }
-
-    /* pub fn get_lookup(&self) -> Option<Res<TypeLookup>> {
-        match self {
-
-        }
-    } */
 }
 
 #[derive(Clone)]
@@ -79,7 +82,8 @@ pub struct View {
 impl mlua::FromLua for View {
     fn from_lua(value: mlua::Value, _: &mlua::Lua) -> mlua::Result<Self> {
         let tyname = value.type_name();
-        value.as_userdata()
+        value
+            .as_userdata()
             .ok_or(mlua::Error::FromLuaConversionError {
                 from: tyname,
                 to: "View".into(),
@@ -100,13 +104,18 @@ impl mlua::UserData for View {
     }
 }
 
+enum QueryResult {
+    None,
+    AlwaysNone,
+    Some(Vec<(mlua::Value, u32)>)
+}
+
 #[derive(Clone)]
 pub struct ViewResult {
     world: ScriptWorldPtr,
-    reflect_iter: Arc<atomic_refcell::AtomicRefCell<ReflectedIteratorOwned>>,
+    reflected_iter: Arc<atomic_refcell::AtomicRefCell<ReflectedIteratorOwned>>,
     /// The queries and the index they would be inserted in the result.
     queries: Vec<(LuaQuery, u32)>,
-    reg_key: Arc<atomic_refcell::AtomicRefCell<Option<mlua::RegistryKey>>>,
 }
 
 unsafe impl Send for ViewResult {}
@@ -120,8 +129,7 @@ impl ViewResult {
 
         for (idx, comp) in items.iter().enumerate() {
             if comp.is_query()? {
-                // Unwrap is safe since `is_query` ensures that the component is convertible.
-                queries.push((LuaQuery::new(comp.as_component().unwrap()), idx as u32));
+                queries.push((comp.as_query(), idx as u32));
                 continue;
             }
 
@@ -129,23 +137,17 @@ impl ViewResult {
                 ViewQueryItem::Table(t) => {
                     let name: String = t.get(mlua::MetaMethod::Type.name())?;
 
-                    let lookup =
-                        w
-                            .get_resource::<TypeLookup>()
-                            .ok_or(mlua::Error::runtime(
-                                "Unable to lookup table proxy, none were ever registered!",
-                            ))?;
+                    let lookup = w.get_resource::<TypeLookup>().ok_or(mlua::Error::runtime(
+                        "Unable to lookup table proxy, none were ever registered!",
+                    ))?;
                     let info = lookup.comp_info_from_name.get(&name).ok_or_else(|| {
                         mlua::Error::BadArgument {
                             to: Some("ViewResult.new".into()),
                             pos: 2 + idx,
                             name: Some("query...".into()),
-                            cause: Arc::new(mlua::Error::external(
-                                WorldError::LuaInvalidUsage(format!(
-                                    "the 'Table' with name {} is unknown to the engine!",
-                                    name
-                                )),
-                            )),
+                            cause: Arc::new(mlua::Error::external(WorldError::LuaInvalidUsage(
+                                format!("the 'Table' with name {} is unknown to the engine!", name),
+                            ))),
                         }
                     })?;
 
@@ -161,7 +163,9 @@ impl ViewResult {
                     let dyn_type = QueryDynamicType::from_info(refl_comp.info);
                     view.push(dyn_type);
                 }
-                _ => todo!(),
+                // functions are queries, the if statement at the start would cause this to
+                // be unreachable.
+                ViewQueryItem::Function(_) => unreachable!()
             }
         }
 
@@ -175,24 +179,24 @@ impl ViewResult {
 
         Ok(Self {
             world,
-            reflect_iter: Arc::new(atomic_refcell::AtomicRefCell::new(reflected_iter)),
+            reflected_iter: Arc::new(AtomicRefCell::new(reflected_iter)),
             queries,
-            reg_key: Arc::new(atomic_refcell::AtomicRefCell::new(None)),
         })
     }
 
     /// Get the next row of components
-    fn next_components(&mut self, lua: &mlua::Lua) -> Result<Option<(Entity, mlua::MultiValue)>, mlua::Error> {
-        let mut query_iter = self.reflect_iter.borrow_mut();
+    fn next_components(
+        &mut self,
+        lua: &mlua::Lua,
+    ) -> Result<Option<(Entity, mlua::MultiValue)>, mlua::Error> {
+        let mut query_iter = self.reflected_iter.borrow_mut();
         if let Some(row) = query_iter.next_lua(lua) {
-            let r = row
+            let (values, _): (Vec<_>, Vec<_>) = row
                 .row
                 .into_iter()
                 .into_iter()
                 .map(|r| (r.comp_val, r.comp_ptr.cast::<()>()))
-                .collect::<Vec<_>>();
-            let (values, _) =
-                itertools::multiunzip::<(Vec<mlua::Value>, Vec<NonNull<()>>), _>(r);
+                .unzip();
             let mult_val = mlua::MultiValue::from_iter(values.into_iter());
             Ok(Some((row.entity, mult_val)))
         } else {
@@ -200,37 +204,36 @@ impl ViewResult {
         }
     }
 
-    /// Get the query results
-    fn get_query_results(&self) -> mlua::Result<Option<Vec<(mlua::Value, u32)>>> {
+    /// Get the query results and the indexes that they were provided in.
+    ///
+    /// The indexes are used to make sure that the results are in the same order that the script
+    /// requested them in.
+    fn get_query_results(&self, entity: Entity) -> mlua::Result<QueryResult> {
         let mut query_vals = vec![];
-        let mut query_allows = true;
+
         for (query, i) in &self.queries {
-            let qres = query.get_query_result(self.world.clone())?;
+            let qres = query.get_query_result(self.world.clone(), entity)?;
             if let Some(val) = qres.as_boolean() {
-                if val {
-                    query_allows = false;
-                    break;
+                // do not push a boolean to values, its considered a filter
+                if !val {
+                    return Ok(QueryResult::None);
                 }
             } else if qres.is_nil() {
-                query_allows = false;
-                break;
+                return Ok(QueryResult::AlwaysNone);
             }
 
             query_vals.push((qres, *i));
         }
 
-        if !query_allows {
-            Ok(None)
-        } else {
-            Ok(Some(query_vals))
-        }
+        Ok(QueryResult::Some(query_vals))
     }
 }
 
 impl mlua::FromLua for ViewResult {
     fn from_lua(value: mlua::Value, _: &mlua::Lua) -> mlua::Result<Self> {
         let tyname = value.type_name();
-        value.as_userdata()
+        value
+            .as_userdata()
             .ok_or(mlua::Error::FromLuaConversionError {
                 from: tyname,
                 to: "View".into(),
@@ -244,65 +247,78 @@ impl mlua::FromLua for ViewResult {
 impl mlua::UserData for ViewResult {
     fn add_methods<M: mlua::UserDataMethods<Self>>(methods: &mut M) {
         methods.add_method_mut("next", |lua, this, ()| {
-            let query_vals = match this.get_query_results()? {
-                Some(v) => v,
-                None => {
-                    return mlua::Value::Nil.into_lua_multi(lua);
-                }
-            };
-
             match this.next_components(lua)? {
                 Some((en, mut vals)) => {
-                    // insert query values to the result row
-                    for (qval, qi) in query_vals {
-                        vals.insert(qi as _, qval);
-                    }
+                    loop {
+                        let query_vals = match this.get_query_results(en)? {
+                            QueryResult::Some(v) => v,
+                            QueryResult::AlwaysNone => {
+                                return mlua::Value::Nil.into_lua_multi(lua);
+                            },
+                            QueryResult::None => {
+                                // try to get it next loop
+                                continue;
+                            }
+                        };
 
-                    vals.push_front(LuaEntityRef::new(this.world.clone(), en).into_lua(lua)?);
-                    Ok(vals)
-                },
-                None => mlua::Value::Nil.into_lua_multi(lua)
+                        // insert query values to the result row
+                        for (qval, qi) in query_vals {
+                            vals.insert(qi as _, qval);
+                        }
+
+                        vals.push_front(LuaEntityRef::new(this.world.clone(), en).into_lua(lua)?);
+                        return Ok(vals);
+                    }
+                }
+                None => mlua::Value::Nil.into_lua_multi(lua),
             }
         });
 
         methods.add_method("iter", |lua, this, ()| {
-            let key_arc = Arc::new(atomic_refcell::AtomicRefCell::new(Some(lua.create_registry_value(this.clone())?)));
+            let key_arc = Arc::new(atomic_refcell::AtomicRefCell::new(Some(
+                lua.create_registry_value(this.clone())?,
+            )));
 
             lua.create_function(move |lua, ()| {
                 let mut key_mut = key_arc.borrow_mut();
-                
+
                 if let Some(key) = key_mut.as_ref() {
-                    let mut this = lua.registry_value::<Self>(&key)?;
+                    let mut this = lua.registry_value::<mlua::UserDataRefMut<Self>>(&key)?;
 
-                    let query_vals = match this.get_query_results()? {
-                        Some(v) => v,
-                        None => {
-                            return mlua::Value::Nil.into_lua_multi(lua);
-                        }
-                    };
+                    loop {
+                        match this.next_components(lua)? {
+                            Some((en, mut vals)) => {
+                                let lua_en =
+                                    LuaEntityRef::new(this.world.clone(), en).into_lua(lua)?;
 
-                    match this.next_components(lua)? {
-                        Some((en, mut vals)) => {
-                            let lua_en = LuaEntityRef::new(this.world, en)
-                                .into_lua(lua)?;
+                                let query_vals = match this.get_query_results(en)? {
+                                    QueryResult::Some(v) => v,
+                                    QueryResult::AlwaysNone => {
+                                        return mlua::Value::Nil.into_lua_multi(lua);
+                                    },
+                                    QueryResult::None => {
+                                        continue;
+                                    }
+                                };
 
-                            // insert query values to the result row
-                            for (qval, qi) in query_vals {
-                                vals.insert(qi as _, qval);
+                                // insert query values to the result row
+                                for (qval, qi) in query_vals {
+                                    vals.insert(qi as _, qval);
+                                }
+
+                                vals.push_front(lua_en);
+                                return Ok(vals);
                             }
+                            None => {
+                                // If this is the last row, remove the registry value
+                                // This doesn't protect against iterators that aren't fully consumed,
+                                // that would cause a leak in the lua registry.
+                                // TODO: fix leak
+                                let key = key_mut.take().unwrap();
+                                lua.remove_registry_value(key)?;
 
-                            vals.push_front(lua_en);
-                            Ok(vals)
-                        },
-                        None => {
-                            // If this is the last row, remove the registry value
-                            // This doesn't protect against iterators that aren't fully consumed,
-                            // that would cause a leak in the lua registry.
-                            // TODO: fix leak
-                            let key = key_mut.take().unwrap();
-                            lua.remove_registry_value(key)?;
-
-                            mlua::Value::Nil.into_lua_multi(lua)
+                                return mlua::Value::Nil.into_lua_multi(lua);
+                            }
                         }
                     }
                 } else {
@@ -311,4 +327,4 @@ impl mlua::UserData for ViewResult {
             })
         });
     }
-}
+}

lyra-scripting/src/lua/entity_ref.rs

@@ -6,7 +6,7 @@ use mlua::{IntoLua, ObjectLike};
 
 use crate::{ScriptBorrow, ScriptWorldPtr};
 
-use super::{reflect_user_data, Error, ReflectLuaProxy, TypeLookup, FN_NAME_INTERNAL_REFLECT_TYPE};
+use super::{reflect_type_user_data, Error, ReflectLuaProxy, TypeLookup, FN_NAME_INTERNAL_REFLECT_TYPE};
 
 #[derive(Clone)]
 pub enum LuaComponent {
@@ -49,7 +49,7 @@ impl LuaComponent {
                 lookup.typeid_from_name.get(&name).cloned()
             }
             Self::UserData(ud) => {
-                let lua_comp = reflect_user_data(ud);
+                let lua_comp = reflect_type_user_data(ud);
                 let refl_comp = lua_comp.reflect_branch.as_component_unchecked();
                 Some(refl_comp.info.type_id().as_rust())
             }
@@ -138,7 +138,7 @@ impl mlua::UserData for LuaEntityRef {
                     let arch = world.entity_archetype_mut(this.en).unwrap();
                     let arch_idx = *arch.entity_indexes().get(&this.en).unwrap();
                     let col = arch.get_column_mut(tid).unwrap();
-                    let col_ptr = col.get_entity_ptr(*arch_idx as usize, &world_tick).cast();
+                    let col_ptr = col.component_ptr(*arch_idx as usize, &world_tick).cast();
                     
                     // get the type registry to apply the new value
                     let reg = world.get_resource::<TypeRegistry>().unwrap();
@@ -149,7 +149,7 @@ impl mlua::UserData for LuaEntityRef {
                         // this should actually be safe since the ReflectedIterator
                         // attempts to get the type data before it is tried here
                         .expect("Type does not have ReflectLuaProxy as a TypeData");
-                    (proxy.fn_apply)(lua, col_ptr, &comp)?;
+                    proxy.apply(lua, col_ptr, &comp)?;
                 }
 
                 Ok(())

lyra-scripting/src/lua/mod.rs

@@ -95,11 +95,16 @@ pub const FN_NAME_INTERNAL_REFLECT: &str = "__lyra_internal_reflect";
 
 /// Name of a Lua function to retrieve the query result from a Userdata, or Table.
 /// 
-/// This function must return a Lua value and take in a single argument: [`ScriptWorldPtr`].
-/// If `nil` is returned, the query in a [`View`](crate::lua::ecs::View) will not provide any
-/// results.\
-/// If it returns a boolean, the result will act as a filter, and the value will not be in
-/// the result.\
+/// The function must match the following definition: `fn(ScriptWorldPtr, Entity) -> LuaValue`.
+/// 
+/// When `nil` is returned, its considered that the query will not result in anything for this
+/// [`View`], **no matter the entity**. When the query is used in a [`View`] and returns `nil`,
+/// it will NOT check for other entities. This is used in the [`ResQuery`] Lua query. If the
+/// resource is missing, it will always be missing for the [`View`], no matter the entity.
+/// 
+/// If it returns a boolean, the query will act as a filter. The boolean value will not be in the
+/// result. When the boolean is `false`, other entities will be checked by the [`View`].
+/// 
 /// Any other value will be included in the result.
 pub const FN_NAME_INTERNAL_ECS_QUERY_RESULT: &str = "__lyra_internal_ecs_query_result";
 
@@ -288,6 +293,16 @@ impl mlua::UserData for ScriptBorrow {
 
 /// Helper function used for reflecting userdata as a ScriptBorrow
 pub fn reflect_user_data(ud: &mlua::AnyUserData) -> ScriptBorrow {
+    let ud_name = ud.metatable().and_then(|mt| mt.get::<String>(mlua::MetaMethod::Type))
+        .unwrap_or("Unknown".to_string());
     ud.call_method::<ScriptBorrow>(FN_NAME_INTERNAL_REFLECT, ())
-        .expect("Type does not implement internal reflect method properly")
+        .unwrap_or_else(|_| panic!("UserData of name '{}' does not implement internal reflect method properly", ud_name))
+}
+
+/// Helper function used for reflecting userdata type as a ScriptBorrow
+pub fn reflect_type_user_data(ud: &mlua::AnyUserData) -> ScriptBorrow {
+    let ud_name = ud.metatable().and_then(|mt| mt.get::<String>(mlua::MetaMethod::Type))
+        .unwrap_or("Unknown".to_string());
+    ud.call_function::<ScriptBorrow>(FN_NAME_INTERNAL_REFLECT_TYPE, ())
+        .unwrap_or_else(|_| panic!("UserData of name '{}' does not implement internal reflect type function properly", ud_name))
 }

lyra-scripting/src/lua/providers/ecs.rs

@@ -1,7 +1,7 @@
 use lyra_ecs::ResourceObject;
 use lyra_reflect::Reflect;
 
-use crate::{lua::{ecs::{query::LuaResQuery, View}, wrappers::*, LuaContext, LuaWrapper, RegisterLuaType, FN_NAME_INTERNAL_REFLECT, FN_NAME_INTERNAL_REFLECT_TYPE}, ScriptApiProvider, ScriptBorrow, ScriptData, ScriptDynamicBundle, ScriptWorldPtr};
+use crate::{lua::{ecs::{query::{LuaChangedQuery, LuaResQuery}, View}, wrappers::*, LuaContext, LuaWrapper, RegisterLuaType, FN_NAME_INTERNAL_REFLECT, FN_NAME_INTERNAL_REFLECT_TYPE}, ScriptApiProvider, ScriptBorrow, ScriptData, ScriptDynamicBundle, ScriptWorldPtr};
 
 //fn register_lua_proxy::<T: 
 
@@ -46,6 +46,7 @@ impl ScriptApiProvider for LyraEcsApiProvider {
         globals.set("Window", ctx.create_proxy::<LuaWindow>()?)?;
         globals.set("View", ctx.create_proxy::<View>()?)?;
         globals.set("ResQuery", ctx.create_proxy::<LuaResQuery>()?)?;
+        globals.set("ChangedQuery", ctx.create_proxy::<LuaChangedQuery>()?)?;
 
         expose_comp_table_wrapper::<LuaCamera>(&ctx, &globals, "Camera")?;
         expose_comp_table_wrapper::<LuaFreeFlyCamera>(&ctx, &globals, "FreeFlyCamera")?;

lyra-scripting/src/lua/proxy.rs

@@ -78,9 +78,9 @@ pub struct TypeLookup {
 /// A struct used for Proxying types to and from Lua.
 #[derive(Clone)]
 pub struct ReflectLuaProxy {
-    pub fn_as_lua:
+    fn_as_lua:
         for<'a> fn(lua: &'a mlua::Lua, this_ptr: NonNull<()>) -> mlua::Result<mlua::Value>,
-    pub fn_apply: for<'a> fn(
+    fn_apply: for<'a> fn(
         lua: &'a mlua::Lua,
         this_ptr: NonNull<()>,
         value: &'a mlua::Value,
@@ -125,6 +125,16 @@ impl ReflectLuaProxy {
             },
         }
     }
+
+    /// Reflect the pointer to get a Lua value.
+    pub fn as_lua(&self, lua: &mlua::Lua, this_ptr: NonNull<()>) -> mlua::Result<mlua::Value> {
+        (self.fn_as_lua)(lua, this_ptr)
+    }
+
+    /// Set the contents in the pointer to a Lua value.
+    pub fn apply(&self, lua: &mlua::Lua, this_ptr: NonNull<()>, value: &mlua::Value) -> mlua::Result<()> {
+        (self.fn_apply)(lua, this_ptr, value)
+    }
 }
 
 impl mlua::FromLua for ScriptDynamicBundle {

lyra-scripting/src/lua/world.rs

@@ -222,7 +222,7 @@ impl mlua::UserData for ScriptWorldPtr {
                                 // this should actually be safe since the ReflectedIterator
                                 // attempts to get the type data before it is tried here
                                 .expect("Type does not have ReflectLuaProxy as a TypeData");
-                            (proxy.fn_apply)(lua, ptr, &comp)?;
+                            proxy.apply(lua, ptr, &comp)?;
                         }
                     } else {
                         let msg = format!(
@@ -262,7 +262,7 @@ impl mlua::UserData for ScriptWorldPtr {
                     .get_data::<ReflectLuaProxy>()
                     .expect("Type does not have ReflectLuaProxy as a TypeData");
 
-                (proxy.fn_as_lua)(lua, res_ptr.cast()).and_then(|ud| ud.into_lua(lua))
+                proxy.as_lua(lua, res_ptr.cast()).and_then(|ud| ud.into_lua(lua))
             } else {
                 // if the resource is not found in the world, return nil
                 Ok(mlua::Value::Nil)