app work

src/layout/id.rs

@@ -141,6 +141,9 @@ pub struct IdFnTag;
 pub trait WidgetIdFn<W>: FnOnce(&mut Ui) -> WidgetId<W> {}
 impl<W, F: FnOnce(&mut Ui) -> WidgetId<W>> WidgetIdFn<W> for F {}
 
+pub trait WidgetRet: FnOnce(&mut Ui) -> WidgetId<AnyWidget> {}
+impl<F: FnOnce(&mut Ui) -> WidgetId<AnyWidget>> WidgetRet for F {}
+
 impl<W: 'static> WidgetLike<IdTag> for WidgetId<W> {
     type Widget = W;
     fn add(self, _: &mut Ui) -> WidgetId<W> {

src/layout/widget.rs

@@ -1,4 +1,7 @@
-use crate::layout::{Len, Painter, SizeCtx, StaticWidgetId, Ui, WidgetId, WidgetIdFn};
+use crate::{
+    core::WidgetPtr,
+    layout::{Len, Painter, SizeCtx, StaticWidgetId, Ui, WidgetId, WidgetIdFn},
+};
 
 use std::{any::Any, marker::PhantomData};
 
@@ -48,6 +51,12 @@ pub trait WidgetLike<Tag> {
     {
         ui.set_root(self);
     }
+    fn set_ptr(self, ptr: &WidgetId<WidgetPtr>, ui: &mut Ui)
+    where
+        Self: Sized,
+    {
+        ui[ptr].inner = Some(self.add(ui).any());
+    }
 }
 
 /// A function that returns a widget given a UI.