sized widgets!

src/layout/widget.rs

@@ -1,9 +1,18 @@
-use crate::layout::{Painter, Ui, WidgetId, WidgetIdFnRet};
+use crate::layout::{Painter, TextData, Textures, Ui, Vec2, WidgetId, WidgetIdFnRet};
 
 use std::{any::Any, marker::PhantomData};
 
 pub trait Widget: Any {
-    fn draw(&self, painter: &mut Painter);
+    fn draw(&mut self, painter: &mut Painter);
+    fn size(&mut self, ctx: SizeCtx) -> Vec2 {
+        ctx.size
+    }
+}
+
+pub struct SizeCtx<'a> {
+    pub size: Vec2,
+    pub text: &'a mut TextData,
+    pub textures: &'a mut Textures,
 }
 
 pub struct WidgetTag;