iris: share resource handle bookkeeping

core/src/util/slot.rs

@@ -5,6 +5,10 @@ pub struct SlotId {
 }
 
 impl SlotId {
+    pub(crate) fn slot(self) -> u32 {
+        self.idx
+    }
+
     /// A stable, collision-free `u64` encoding of this id -- for a caller
     /// (accesskit's `NodeId`, today) that wants a flat integer key rather
     /// than the two `u32`s. `idx` is offset by one so no real id ever
@@ -18,6 +22,7 @@ impl SlotId {
 pub struct SlotVec<T> {
     data: Vec<(u32, Option<T>)>,
     free: Vec<u32>,
+    len: usize,
 }
 
 impl<T> SlotVec<T> {
@@ -25,11 +30,12 @@ impl<T> SlotVec<T> {
         Self {
             data: Default::default(),
             free: Default::default(),
+            len: 0,
         }
     }
 
     pub fn add(&mut self, x: T) -> SlotId {
-        if let Some(idx) = self.free.pop() {
+        let id = if let Some(idx) = self.free.pop() {
             let (genr, data) = &mut self.data[idx as usize];
             *data = Some(x);
             SlotId { idx, genr: *genr }
@@ -38,14 +44,35 @@ impl<T> SlotVec<T> {
             let genr = 0;
             self.data.push((genr, Some(x)));
             SlotId { idx, genr }
-        }
+        };
+        self.len += 1;
+        id
     }
 
     pub fn free(&mut self, id: SlotId) {
+        let _ = self.remove(id);
+    }
+
+    pub fn remove(&mut self, id: SlotId) -> Option<T> {
+        self.remove_inner(id, true)
+    }
+
+    pub fn remove_unrecycled(&mut self, id: SlotId) -> Option<T> {
+        self.remove_inner(id, false)
+    }
+
+    fn remove_inner(&mut self, id: SlotId, recycle: bool) -> Option<T> {
         let (genr, data) = &mut self.data[id.idx as usize];
+        if *genr != id.genr {
+            return None;
+        }
         *genr += 1;
-        *data = None;
-        self.free.push(id.idx);
+        let value = data.take()?;
+        self.len -= 1;
+        if recycle {
+            self.free.push(id.idx);
+        }
+        Some(value)
     }
 
     pub fn get(&self, id: SlotId) -> Option<&T> {
@@ -65,7 +92,7 @@ impl<T> SlotVec<T> {
     }
 
     pub fn len(&self) -> usize {
-        self.data.len() - self.free.len()
+        self.len
     }
 
     pub fn is_empty(&self) -> bool {
@@ -75,6 +102,10 @@ impl<T> SlotVec<T> {
     pub fn values_mut(&mut self) -> impl Iterator<Item = &mut T> {
         self.data.iter_mut().filter_map(|(_, value)| value.as_mut())
     }
+
+    pub fn capacity(&self) -> usize {
+        self.data.len()
+    }
 }
 
 impl<T> Default for SlotVec<T> {