widget fn ret macro

src/layout/widget.rs

@@ -59,9 +59,17 @@ pub trait WidgetLike {
 /// A function that returns a widget given a UI.
 /// Useful for defining trait functions on widgets that create a parent widget so that the children
 /// don't need to be IDs yet
+pub trait WFn<W> = FnOnce(&mut Ui) -> W;
 pub struct WidgetFn<F: FnOnce(&mut Ui) -> W, W>(pub F);
 pub struct WidgetIdFn<F: FnOnce(&mut Ui) -> WidgetId<W>, W>(pub F);
 
+macro_rules! WidgetFnRet {
+    ($W:ident) => {
+        WidgetFn<impl FnOnce(&mut Ui) -> $W, $W>
+    };
+}
+pub(crate) use WidgetFnRet;
+
 pub trait _WidgetFn<W: Widget> {
     fn call(ui: &mut Ui) -> W;
 }