trying to get new Bsp to work; update docs

layout/src/measure.rs

@@ -1,5 +1,6 @@
 use crate::*;
 use std::sync::{Arc, atomic::{AtomicUsize, Ordering::Relaxed}};
+use ratatui::prelude::{Style, Color};
 
 // TODO: 🡘  🡙 ←🡙→ indicator to expand window when too small
 
@@ -79,3 +80,43 @@ impl<E: Engine> Measure<E> {
 //}
 
 //impl<E: Engine> ContentDebug<E> for E {}
+
+impl Render<Tui> for Measure<Tui> {
+    fn min_size (&self, _: [u16;2]) -> Perhaps<[u16;2]> {
+        Ok(Some([0u16.into(), 0u16.into()].into()))
+    }
+    fn render (&self, to: &mut TuiOutput) -> Usually<()> {
+        self.set_w(to.area().w());
+        self.set_h(to.area().h());
+        Ok(())
+    }
+}
+
+impl Measure<Tui> {
+    pub fn debug (&self) -> ShowMeasure {
+        ShowMeasure(&self)
+    }
+}
+
+render!(<Tui>|self: ShowMeasure<'a>|render(|to: &mut TuiOutput|Ok({
+    let w = self.0.w();
+    let h = self.0.h();
+    to.blit(&format!(" {w} x {h} "), to.area.x(), to.area.y(), Some(
+        Style::default().bold().italic().bg(Color::Rgb(255, 0, 255)).fg(Color::Rgb(0,0,0))
+    ))
+})));
+
+pub struct ShowMeasure<'a>(&'a Measure<Tui>);
+
+pub struct DebugOverlay<E: Engine, W: Render<E>>(PhantomData<E>, pub W);
+
+impl<T: Render<Tui>> Render<Tui> for DebugOverlay<Tui, T> {
+    fn min_size (&self, to: [u16;2]) -> Perhaps<[u16;2]> {
+        self.1.min_size(to)
+    }
+    fn render (&self, to: &mut TuiOutput) -> Usually<()> {
+        let [x, y, w, h] = to.area();
+        self.1.render(to)?;
+        Ok(to.blit(&format!("{w}x{h}+{x}+{y}"), x, y, Some(Style::default().green())))
+    }
+}