switch away from handles to refs that must be upgraded once

core/src/widget/widgets.rs

@@ -1,15 +1,27 @@
+use std::sync::mpsc::Sender;
+
 use crate::{
-    IdLike, Widget, WidgetData, WidgetId,
+    IdLike, Widget, WidgetData, WidgetHandle, WidgetId, WidgetRef,
     util::{DynBorrower, HashSet, SlotVec, forget_mut, to_mut},
 };
 
-#[derive(Default)]
 pub struct Widgets {
     pub needs_redraw: HashSet<WidgetId>,
     vec: SlotVec<WidgetData>,
+    send: Sender<WidgetId>,
+    pub(crate) waiting: HashSet<WidgetId>,
 }
 
 impl Widgets {
+    pub fn new(send: Sender<WidgetId>) -> Self {
+        Self {
+            needs_redraw: Default::default(),
+            vec: Default::default(),
+            waiting: Default::default(),
+            send,
+        }
+    }
+
     pub fn has_updates(&self) -> bool {
         !self.needs_redraw.is_empty()
     }
@@ -37,20 +49,37 @@ impl Widgets {
 
     pub fn get<I: IdLike>(&self, id: &I) -> Option<&I::Widget>
     where
-        I::Widget: Sized,
+        I::Widget: Sized + Widget,
     {
         self.get_dyn(id.id())?.as_any().downcast_ref()
     }
 
     pub fn get_mut<I: IdLike>(&mut self, id: &I) -> Option<&mut I::Widget>
     where
-        I::Widget: Sized,
+        I::Widget: Sized + Widget,
     {
         self.get_dyn_mut(id.id())?.as_any_mut().downcast_mut()
     }
 
-    pub fn add<W: Widget>(&mut self, widget: W) -> WidgetId {
-        self.vec.add(WidgetData::new(widget))
+    pub fn add_strong<W: Widget>(&mut self, widget: W) -> WidgetHandle<W> {
+        let id = self.vec.add(WidgetData::new(widget));
+        WidgetHandle::new(id, self.send.clone())
+    }
+
+    pub fn add_weak<W: Widget>(&mut self, widget: W) -> WidgetRef<W> {
+        let id = self.vec.add(WidgetData::new(widget));
+        self.waiting.insert(id);
+        WidgetRef::new(id)
+    }
+
+    #[track_caller]
+    pub fn upgrade<W: ?Sized>(&mut self, rf: WidgetRef<W>) -> WidgetHandle<W> {
+        if !self.waiting.remove(&rf.id()) {
+            let label = self.label(rf);
+            let id = rf.id();
+            panic!("widget '{label}' ({id:?}) was already added\ncannot add a widget twice; consider creating two")
+        }
+        WidgetHandle::new(rf.id(), self.send.clone())
     }
 
     pub fn data(&self, id: impl IdLike) -> Option<&WidgetData> {