refcount ids and delete unused

src/layout/ui.rs

@@ -6,6 +6,7 @@ use crate::{
 use std::{
     any::{Any, TypeId},
     ops::{Index, IndexMut},
+    sync::mpsc::{Receiver, Sender, channel},
 };
 
 pub struct Ui<Ctx> {
@@ -13,6 +14,8 @@ pub struct Ui<Ctx> {
     base: Option<WidgetId>,
     widgets: Widgets<Ctx>,
     updates: Vec<WidgetId>,
+    del_recv: Receiver<Id>,
+    del_send: Sender<Id>,
     pub(super) active_sensors: ActiveSensors,
     pub(super) sensor_map: SensorMap<Ctx>,
     primitives: Primitives,
@@ -35,9 +38,9 @@ impl<Ctx> Ui<Ctx> {
     }
 
     pub fn push<W: Widget<Ctx>>(&mut self, w: W) -> WidgetId<W> {
-        let id = self.ids.next();
-        self.widgets.insert(id.duplicate(), w);
-        WidgetId::new(id, TypeId::of::<W>())
+        let id = self.id();
+        self.widgets.insert(id.id.duplicate(), w);
+        id
     }
 
     pub fn set<W: Widget<Ctx>>(&mut self, i: &WidgetId<W>, w: W) {
@@ -65,7 +68,7 @@ impl<Ctx> Ui<Ctx> {
     }
 
     pub fn id<W: Widget<Ctx>>(&mut self) -> WidgetId<W> {
-        WidgetId::new(self.ids.next(), TypeId::of::<W>())
+        WidgetId::new(self.ids.next(), TypeId::of::<W>(), self.del_send.clone())
     }
 
     pub fn redraw_all(&mut self, ctx: &mut Ctx)
@@ -89,6 +92,10 @@ impl<Ctx> Ui<Ctx> {
     where
         Ctx: 'static,
     {
+        while let Ok(id) = self.del_recv.try_recv() {
+            self.widgets.delete(id);
+        }
+
         if self.full_redraw {
             self.redraw_all(ctx);
             self.full_redraw = false;
@@ -105,6 +112,10 @@ impl<Ctx> Ui<Ctx> {
     pub fn needs_redraw(&self) -> bool {
         self.full_redraw || !self.updates.is_empty()
     }
+
+    pub fn num_widgets(&self) -> usize {
+        self.widgets.len()
+    }
 }
 
 impl<W: Widget<Ctx>, Ctx> Index<&WidgetId<W>> for Ui<Ctx> {
@@ -146,6 +157,18 @@ impl<Ctx> Widgets<Ctx> {
     pub fn insert_any(&mut self, id: Id, widget: Box<dyn Widget<Ctx>>) {
         self.0.insert(id, widget);
     }
+
+    pub fn delete(&mut self, id: Id) {
+        self.0.remove(&id);
+    }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
 }
 
 impl<Ctx> dyn Widget<Ctx> {
@@ -160,6 +183,7 @@ impl<Ctx> dyn Widget<Ctx> {
 
 impl<Ctx: 'static> Default for Ui<Ctx> {
     fn default() -> Self {
+        let (del_send, del_recv) = channel();
         Self {
             ids: Default::default(),
             base: Default::default(),
@@ -169,6 +193,8 @@ impl<Ctx: 'static> Default for Ui<Ctx> {
             full_redraw: false,
             active_sensors: Default::default(),
             sensor_map: Default::default(),
+            del_send,
+            del_recv,
         }
     }
 }