indices iterator for layers

src/core/sense.rs

@@ -138,10 +138,10 @@ impl<Ctx> SensorModule<Ctx> {
 
 impl<Ctx: UiCtx + 'static> SensorModule<Ctx> {
     pub fn run(ctx: &mut Ctx, cursor: &CursorState, window_size: Vec2) {
-        let mut layers = std::mem::take(&mut ctx.ui().layers);
+        let layers = std::mem::take(&mut ctx.ui().layers);
         let mut module = std::mem::take(ctx.ui().modules.get_mut::<Self>());
 
-        for (i, _) in layers.iter_mut().rev() {
+        for i in layers.indices().rev() {
             let Some(list) = module.active.get_mut(&i) else {
                 continue;
             };

src/layout/layer.rs

@@ -95,15 +95,11 @@ impl Layers {
     }
 
     pub fn iter_mut(&mut self) -> LayerIteratorMut<'_> {
-        let mut last = 0;
-        while let Some(c) = self.vec[last].child {
-            last = c.tail;
-        }
-        LayerIteratorMut {
-            next: Some(0),
-            next_back: Some(last),
-            vec: &mut self.vec,
-        }
+        LayerIteratorMut::new(&mut self.vec)
+    }
+
+    pub fn indices(&self) -> LayerIndexIterator<'_> {
+        LayerIndexIterator::new(&self.vec)
     }
 
     pub fn write<P: Primitive>(
@@ -157,18 +153,51 @@ impl LayerNode {
 }
 
 pub struct LayerIteratorMut<'a> {
-    next: Option<usize>,
-    next_back: Option<usize>,
-    vec: &'a mut Vec<LayerNode>,
+    inner: LayerIndexIterator<'a>,
 }
 
 impl<'a> Iterator for LayerIteratorMut<'a> {
     type Item = (usize, &'a mut Layer);
 
+    fn next(&mut self) -> Option<Self::Item> {
+        let i = self.inner.next()?;
+        // SAFETY: requires index iterator to work properly
+        #[allow(mutable_transmutes)]
+        let layer: &mut Layer = unsafe { std::mem::transmute(&self.inner.vec[i]) };
+        Some((i, layer))
+    }
+}
+
+impl<'a> DoubleEndedIterator for LayerIteratorMut<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let i = self.inner.next_back()?;
+        // SAFETY: requires index iterator to work properly
+        #[allow(mutable_transmutes)]
+        let layer: &mut Layer = unsafe { std::mem::transmute(&self.inner.vec[i]) };
+        Some((i, layer))
+    }
+}
+
+impl<'a> LayerIteratorMut<'a> {
+    fn new(vec: &'a mut Vec<LayerNode>) -> Self {
+        Self {
+            inner: LayerIndexIterator::new(vec),
+        }
+    }
+}
+
+pub struct LayerIndexIterator<'a> {
+    next: Option<usize>,
+    next_back: Option<usize>,
+    vec: &'a Vec<LayerNode>,
+}
+
+impl<'a> Iterator for LayerIndexIterator<'a> {
+    type Item = usize;
+
     fn next(&mut self) -> Option<Self::Item> {
         let ret_i = self.next?;
-        // chat are we cooked? (if it's not set up correctly this could be catastrophic)
-        let node: &mut LayerNode = unsafe { std::mem::transmute(&mut self.vec[ret_i]) };
+        let node = &self.vec[ret_i];
         self.next = if let Some(c) = node.child {
             Some(c.head)
         } else if let Ptr::Next(i) = node.next {
@@ -187,14 +216,14 @@ impl<'a> Iterator for LayerIteratorMut<'a> {
             self.next = None;
             self.next_back = None;
         }
-        Some((ret_i, &mut node.data))
+        Some(ret_i)
     }
 }
 
-impl<'a> DoubleEndedIterator for LayerIteratorMut<'a> {
+impl<'a> DoubleEndedIterator for LayerIndexIterator<'a> {
     fn next_back(&mut self) -> Option<Self::Item> {
         let ret_i = self.next_back?;
-        let node: &mut LayerNode = unsafe { std::mem::transmute(&mut self.vec[ret_i]) };
+        let node = &self.vec[ret_i];
         self.next_back = if let Ptr::Next(mut i) = node.prev {
             while let Some(c) = self.vec[i].child {
                 i = c.tail
@@ -209,6 +238,20 @@ impl<'a> DoubleEndedIterator for LayerIteratorMut<'a> {
             self.next = None;
             self.next_back = None;
         }
-        Some((ret_i, &mut node.data))
+        Some(ret_i)
+    }
+}
+
+impl<'a> LayerIndexIterator<'a> {
+    fn new(vec: &'a Vec<LayerNode>) -> Self {
+        let mut last = 0;
+        while let Some(c) = vec[last].child {
+            last = c.tail;
+        }
+        Self {
+            next: Some(0),
+            next_back: Some(last),
+            vec,
+        }
     }
 }