refactor out typemap

core/src/event/manager.rs

@@ -1,25 +1,17 @@
 use crate::{
     ActiveData, Event, EventCtx, EventFn, EventLike, IdLike, LayerId, Ui, WidgetData, WidgetId,
-    util::HashMap,
-};
-use std::{
-    any::{Any, TypeId},
-    rc::Rc,
+    util::{HashMap, TypeMap},
 };
+use std::{any::TypeId, rc::Rc};
 
 #[derive(Default)]
 pub struct EventManager {
-    types: HashMap<TypeId, Box<dyn EventManagerLike>>,
+    types: TypeMap<dyn EventManagerLike>,
 }
 
 impl EventManager {
     pub fn get_type<E: EventLike, Ctx: 'static>(&mut self) -> &mut TypeEventManager<E::Event, Ctx> {
-        self.types
-            .entry(Self::type_key::<E, Ctx>())
-            .or_insert(Box::new(TypeEventManager::<E::Event, Ctx>::default()))
-            .as_any()
-            .downcast_mut()
-            .unwrap()
+        self.types.type_or_default()
     }
 
     pub fn register<I: IdLike, E: EventLike, Ctx: 'static>(
@@ -58,7 +50,6 @@ pub trait EventManagerLike {
     fn remove(&mut self, id: WidgetId);
     fn draw(&mut self, data: &ActiveData);
     fn undraw(&mut self, data: &ActiveData);
-    fn as_any(&mut self) -> &mut dyn Any;
 }
 
 type EventData<E, Ctx> = (E, Rc<dyn for<'a> EventFn<Ctx, <E as Event>::Data<'a>>>);
@@ -87,9 +78,6 @@ impl<E: Event, Ctx: 'static> EventManagerLike for TypeEventManager<E, Ctx> {
             layer.remove(&data.id);
         }
     }
-    fn as_any(&mut self) -> &mut dyn Any {
-        self
-    }
 }
 
 impl<E: Event, Ctx> Default for TypeEventManager<E, Ctx> {

core/src/util/mod.rs

@@ -1,19 +1,21 @@
+mod typemap;
 mod arena;
 mod borrow;
 mod change;
-mod slot;
 mod id;
 mod math;
 mod refcount;
+mod slot;
 mod vec2;
 
+pub use typemap::*;
 pub use arena::*;
 pub use borrow::*;
 pub use change::*;
-pub use slot::*;
 pub use id::*;
 pub use math::*;
 pub use refcount::*;
+pub use slot::*;
 pub use vec2::*;
 
 pub type HashMap<K, V> = fxhash::FxHashMap<K, V>;

core/src/util/typemap.rs

@@ -0,0 +1,56 @@
+use crate::util::HashMap;
+use std::{
+    any::TypeId,
+    marker::Unsize,
+    ops::{Deref, DerefMut},
+};
+
+pub struct TypeMap<Trait: ?Sized> {
+    map: HashMap<TypeId, Box<Trait>>,
+}
+
+impl<Trait: ?Sized> TypeMap<Trait> {
+    pub fn set_type<T: Unsize<Trait> + 'static>(&mut self, val: T) {
+        self.map
+            .insert(TypeId::of::<T>(), Box::new(val) as Box<Trait>);
+    }
+
+    pub fn type_mut<T: Unsize<Trait> + 'static>(&mut self) -> Option<&mut T> {
+        Some(Self::convert_mut(self.map.get_mut(&TypeId::of::<T>())?))
+    }
+
+    pub fn type_or_default<T: Default + Unsize<Trait> + 'static>(&mut self) -> &mut T {
+        Self::convert_mut(
+            self.map
+                .entry(TypeId::of::<T>())
+                .or_insert(Box::new(T::default()) as Box<Trait>),
+        )
+    }
+
+    fn convert_mut<T: Unsize<Trait>>(entry: &mut Box<Trait>) -> &mut T {
+        // allegedly this is just what Any does...
+        unsafe { &mut *(entry.as_mut() as *mut Trait as *mut T) }
+    }
+}
+
+impl<T: ?Sized> Deref for TypeMap<T> {
+    type Target = HashMap<TypeId, Box<T>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.map
+    }
+}
+
+impl<T: ?Sized> DerefMut for TypeMap<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.map
+    }
+}
+
+impl<T: ?Sized> Default for TypeMap<T> {
+    fn default() -> Self {
+        Self {
+            map: Default::default(),
+        }
+    }
+}