made painter actually how I wanted it (draw now takes in an owned painter)

src/layout/widget.rs

@@ -2,7 +2,7 @@ use crate::{Painter, Ui, WidgetId, WidgetIdFnRet};
 use std::{any::Any, marker::PhantomData};
 
 pub trait Widget<Ctx>: Any {
-    fn draw(&self, painter: &mut Painter<Ctx>);
+    fn draw(&self, painter: Painter<Ctx>);
 }
 
 pub struct WidgetTag;