diff --git a/examples/tui_00.rs b/examples/tui_00.rs
index 94bf069..80e7acd 100644
--- a/examples/tui_00.rs
+++ b/examples/tui_00.rs
@@ -4,7 +4,6 @@ namespace!(State: bool  {});
 namespace!(State: u16   {});
 namespace!(State: Color {});
    handle!(TuiIn: |self: State, input|Action::from(input).eval(self).map(|_|None));
-     from!(Action: |input: &TuiIn| todo!());
      view!(State: TuiOut: [ evaluate_output_expression, evaluate_output_expression_tui ]);
      draw!(State: TuiOut: [ draw_example ]);
 #[derive(Debug, Default)] struct State {
@@ -12,6 +11,7 @@ namespace!(State: Color {});
     /** Command history (undo/redo) */ history: Vec<Action>,
     /** User-controllable value     */ cursor:  usize,
 }
+impl_from!(Action: |input: &TuiIn| todo!());
 #[derive(Debug)] enum Action {
     /** Increment cursor */ Next,
     /** Decrement cursor */ Prev
diff --git a/src/tengri.rs b/src/tengri.rs
index fd0560e..7c1968b 100644
--- a/src/tengri.rs
+++ b/src/tengri.rs
@@ -36,7 +36,7 @@ pub extern crate unicode_width; pub(crate) use unicode_width::*;
 };
 pub(crate) use ::std::{
     io::{stdout, Stdout, Write},
-    sync::{Arc, RwLock, atomic::{AtomicBool, AtomicUsize, Ordering::*}},
+    sync::{Arc, Weak, RwLock, atomic::{AtomicBool, AtomicUsize, Ordering::*}},
     fmt::{Debug, Display},
     ops::{Add, Sub, Mul, Div},
     marker::PhantomData,
@@ -156,8 +156,6 @@ pub(crate) use ::std::{
     }
 }
 
-
-
 /// Define layout operation.
 ///
 /// ```
diff --git a/src/tengri_impl.rs b/src/tengri_impl.rs
index 3b3d1ea..0a865c2 100644
--- a/src/tengri_impl.rs
+++ b/src/tengri_impl.rs
@@ -37,7 +37,7 @@ impl<'a, T: AsRef<str>> TrimString<T> {
     fn as_ref (&self) -> TrimStringRef<'_, T> { TrimStringRef(self.0, &self.1) }
 }
 impl<O: Out, T: Draw<O>> ErrorBoundary<O, T> {
-    pub fn new (content: Perhaps<T>) -> Self { Self(Default::default(), content) }
+    pub fn new (content: Perhaps<T>) -> Self { Self(content, Default::default()) }
 }
 impl<O: Out, T, L: Content<O>, V: Content<O>> HasContent<O> for FieldH<T, L, V> {
     fn content (&self) -> impl Content<O> { Bsp::e(&self.1, &self.2) }
@@ -89,9 +89,6 @@ impl<S, T: Command<S>> Command<S> for Option<T> {
         Ok(None)
     }
 }
-impl<O: Out, T: Content<O>, F: Fn()->T> Lazy<O, T, F> {
-    pub const fn new (thunk: F) -> Self { Self(thunk, PhantomData) }
-}
 impl<O: Out> Layout<O> for Measure<O> {}
 impl<E: Out, T: AsRef<Measure<E>>> Measured<E> for T {
     fn measure (&self) -> &Measure<E> { self.as_ref() }
@@ -102,14 +99,16 @@ impl<O: Out> Clone for Measure<O> {
     }
 }
 impl<O: Out, F: Fn(&mut O)> Thunk<O, F> {
-    pub const fn new (draw: F) -> Self { Self(PhantomData, draw) }
+    pub const fn new (draw: F) -> Self { Self(draw, PhantomData) }
 }
 impl<O: Out, F: Fn(&mut O)> Draw<O> for Thunk<O, F> {
-    fn draw (&self, to: &mut O) { (self.1)(to) }
+    fn draw (&self, to: &mut O) { (self.0)(to) }
 }
 impl<O: Out, F: Fn(&mut O)> Layout<O> for Thunk<O, F> {}
 impl<T: PartialEq, U> Memo<T, U> {
-    pub fn new (value: T, view: U) -> Self { Self { value, view: Arc::new(view.into()) } }
+    pub fn new (value: T, view: U) -> Self {
+        Self { value, view: Arc::new(view.into()) }
+    }
     pub fn update <R> (&mut self, newval: T, draw: impl Fn(&mut U, &T, &T)->R) -> Option<R> {
         if newval != self.value {
             let result = draw(&mut*self.view.write().unwrap(), &newval, &self.value);
@@ -528,7 +527,7 @@ impl<O: Out, Head: Layout<O>, Tail: Layout<O>> Layout<O> for Bsp<Head, Tail> {
     fn layout_w (&self, area: XYWH<O::Unit>) -> O::Unit {
         match self.0 {
             Above | Below | North | South => self.1.layout_w(area).max(self.2.layout_w(area)),
-            East  | West  => self.1.layout_w_min(area).plus(self.2.layout_w(area)),  
+            East  | West  => self.1.layout_w_min(area).plus(self.2.layout_w(area)),
         }
     }
     fn layout_w_min (&self, area: XYWH<O::Unit>) -> O::Unit {
@@ -546,7 +545,7 @@ impl<O: Out, Head: Layout<O>, Tail: Layout<O>> Layout<O> for Bsp<Head, Tail> {
     fn layout_h (&self, area: XYWH<O::Unit>) -> O::Unit {
         match self.0 {
             Above | Below | East  | West  => self.1.layout_h(area).max(self.2.layout_h(area)),
-            North | South => self.1.layout_h(area).plus(self.2.layout_h(area)),      
+            North | South => self.1.layout_h(area).plus(self.2.layout_h(area)),
         }
     }
     fn layout_h_min (&self, area: XYWH<O::Unit>) -> O::Unit {
@@ -558,7 +557,7 @@ impl<O: Out, Head: Layout<O>, Tail: Layout<O>> Layout<O> for Bsp<Head, Tail> {
     fn layout_h_max (&self, area: XYWH<O::Unit>) -> O::Unit {
         match self.0 {
             Above | Below | North | South => self.1.layout_h_max(area).max(self.2.layout_h_max(area)),
-            East  | West  => self.1.layout_h_max(area).plus(self.2.layout_h_max(area)), 
+            East  | West  => self.1.layout_h_max(area).plus(self.2.layout_h_max(area)),
         }
     }
     fn layout (&self, area: XYWH<O::Unit>) -> XYWH<O::Unit> {
@@ -871,60 +870,119 @@ mod xywh {
     impl_from!(ItemColor: |okhsl: Okhsl<f32>| Self { okhsl, rgb: okhsl_to_rgb(okhsl) });
     impl_debug!(BigBuffer |self, f| { write!(f, "[BB {}x{} ({})]", self.width, self.height, self.content.len()) });
     impl Tui {
+        /// True if done
+        pub fn exited (&self) -> bool { self.exited.fetch_and(true, Relaxed) }
+        /// Prepare before run
+        pub fn setup (&self) -> Usually<()> { tui_setup(&mut*self.backend.write().unwrap()) }
+        /// Clean up after run
+        pub fn teardown (&self) -> Usually<()> { tui_teardown(&mut*self.backend.write().unwrap()) }
+        /// Apply changes to the display buffer.
+        pub fn flip (&mut self, mut buffer: Buffer, size: ratatui::prelude::Rect) -> Buffer {
+            tui_resized(&mut*self.backend.write().unwrap(), &mut*self.buffer.write().unwrap(), size);
+            tui_redrawn(&mut*self.backend.write().unwrap(), &mut*self.buffer.write().unwrap(), &mut buffer);
+            buffer
+        }
+        /// Create the engine.
         pub fn new (output: Box<dyn Write + Send + Sync>) -> Usually<Self> {
             let backend = CrosstermBackend::new(output);
             let Size { width, height } = backend.size()?;
             Ok(Self {
                 exited:  Arc::new(AtomicBool::new(false)),
-                buffer:  Buffer::empty(Rect { x: 0, y: 0, width, height }),
-                area:    [0, 0, width, height],
+                buffer:  Buffer::empty(Rect { x: 0, y: 0, width, height }).into(),
+                area:    XYWH(0, 0, width, height),
                 perf:    Default::default(),
-                backend,
+                backend: backend.into(),
+                event:   None,
+                error:   None,
             })
         }
-        /// Create and launch a terminal user interface.
-        pub fn run <T> (self, join: bool, state: &Arc<RwLock<T>>) -> Usually<Arc<RwLock<Self>>> where
-            T: Handle<TuiIn> + Draw<TuiOut> + Send + Sync + 'static
+        /// Run an amm in the engine.
+        pub fn run <T> (mut self, join: bool, state: &Arc<RwLock<T>>) -> Usually<Arc<Self>> where
+            T: Handle<Tui> + Draw<Tui> + Send + Sync + 'static
         {
-            let tui = Arc::new(RwLock::new(self));
-            let _input_thread = tui_input(tui.clone(), state, Duration::from_millis(100));
-            tui.write().unwrap().setup()?;
-            let render_thread = tui_output(tui.clone(), state, Duration::from_millis(10))?;
+            self.setup()?;
+            let tui = Arc::new(self);
+            let _input_thread = tui_input(&tui, state, Duration::from_millis(100))?;
+            let render_thread = tui_output(&tui, state, Duration::from_millis(10))?;
             if join {
-                match render_thread.join() {
-                    Ok(result) => {
-                        tui.write().unwrap().teardown()?;
-                        println!("\n\rRan successfully: {result:?}\n\r");
-                    },
-                    Err(error) => {
-                        tui.write().unwrap().teardown()?;
-                        panic!("\n\rDraw thread failed: error={error:?}.\n\r")
-                    },
+                let result = render_thread.join();
+                tui.teardown()?;
+                match result {
+                    Ok(result) => println!("\n\rRan successfully: {result:?}\n\r"),
+                    Err(error) => panic!("\n\rDraw thread failed: error={error:?}.\n\r"),
                 }
             }
             Ok(tui)
         }
-        /// True if done
-        pub fn exited (&self) -> bool { self.exited.fetch_and(true, Relaxed) }
-        /// Prepare before run
-        pub fn setup (&mut self) -> Usually<()> { tui_setup(&mut self.backend) }
-        /// Clean up after run
-        pub fn teardown (&mut self) -> Usually<()> { tui_teardown(&mut self.backend) }
-        /// Apply changes to the display buffer.
-        pub fn flip (&mut self, mut buffer: Buffer, size: ratatui::prelude::Rect) -> Buffer {
-            tui_resized(&mut self.backend, &mut self.buffer, size);
-            tui_redrawn(&mut self.backend, &mut self.buffer, &mut buffer);
-            buffer
+    }
+
+    /// Spawn the input thread.
+    pub fn tui_input <T: Handle<Tui> + Send + Sync + 'static> (
+        engine: &Arc<Tui>, state: &Arc<RwLock<T>>, poll: Duration
+    ) -> Result<TuiThread, std::io::Error> {
+        let state = state.clone();
+        let engine = engine.clone();
+        TuiThread::new_poll(engine.exited.clone(), poll, move |_| {
+            let event = read().unwrap();
+            match event {
+                Event::Key(KeyEvent {
+                    modifiers: KeyModifiers::CONTROL,
+                    code:      KeyCode::Char('c'),
+                    kind:      KeyEventKind::Press,
+                    state:     KeyEventState::NONE
+                }) => {
+                    engine.exited.store(true, Relaxed);
+                },
+                _ => {
+                    let event = TuiEvent::from_crossterm(event);
+                    if let Err(e) = state.write().unwrap().handle(&engine) {
+                        panic!("{e}")
+                    }
+                }
+            }
+        })
+    }
+
+    /// Spawn the output thread.
+    pub fn tui_output <T: Draw<Tui> + Send + Sync + 'static> (
+        engine: &Arc<Tui>, state: &Arc<RwLock<T>>, sleep: Duration
+    ) -> Result<TuiThread, std::io::Error> {
+        let state = state.clone();
+        let mut engine = engine.clone();
+        let WH(width, height) = tui_wh(&engine);
+        let mut buffer = Buffer::empty(Rect { x: 0, y: 0, width, height });
+        TuiThread::new_sleep(engine.exited.clone(), sleep, move |perf| {
+            let WH(width, height) = tui_wh(&engine);
+            if let Ok(state) = state.try_read() {
+                let size = Rect { x: 0, y: 0, width, height };
+                if buffer.area != size {
+                    engine.backend.write().unwrap()
+                        .clear_region(ClearType::All).expect("pre-frame clear region failed");
+                    buffer.resize(size);
+                    buffer.reset();
+                }
+                state.draw(&engine);
+                buffer = engine.flip(*engine.buffer.write().unwrap(), size);
+            }
+            let timer = format!("{:>3.3}ms", perf.used.load(Relaxed));
+            buffer.set_string(0, 0, &timer, Style::default());
+        })
+    }
+
+    fn tui_wh (engine: &Tui) -> WH<u16> {
+        let Size { width, height } = engine.backend.read().unwrap().size().expect("get size failed");
+        WH(width, height)
+    }
+
+    impl Input for Tui {
+        type Event = TuiEvent;
+        type Handled = bool;
+        fn event (&self) -> &TuiEvent {
+            self.event.as_ref().expect("input.event called outside of input handler")
         }
     }
 
-    impl Input for TuiIn {
-        type Event = TuiEvent;
-        type Handled = bool;
-        fn event (&self) -> &TuiEvent { &self.event }
-    }
-
-    impl Done for TuiIn {
+    impl Done for Tui {
         fn done (&self) { self.exited.store(true, Relaxed); }
         fn is_done (&self) -> bool { self.exited.fetch_and(true, Relaxed) }
     }
@@ -1003,7 +1061,7 @@ mod xywh {
         }
     }
 
-    impl Out for TuiOut {
+    impl Out for Tui {
         type Unit = u16;
         #[inline] fn area (&self) -> XYWH<u16> { self.area }
         #[inline] fn area_mut (&mut self) -> &mut XYWH<u16> { &mut self.area }
@@ -1015,9 +1073,11 @@ mod xywh {
         }
     }
 
-    impl TuiOut {
+    impl Tui {
         #[inline] pub fn with_rect (&mut self, area: XYWH<u16>) -> &mut Self { self.area = area; self }
-        pub fn update    (&mut self, area: XYWH<u16>, callback: &impl Fn(&mut Cell, u16, u16)) { tui_update(&mut self.buffer, area, callback); }
+        pub fn update    (&mut self, area: XYWH<u16>, callback: &impl Fn(&mut Cell, u16, u16)) {
+            tui_update(&mut*self.buffer.write().unwrap(), area, callback);
+        }
         pub fn fill_char (&mut self, area: XYWH<u16>, c: char) { self.update(area, &|cell,_,_|{cell.set_char(c);}) }
         pub fn fill_bg   (&mut self, area: XYWH<u16>, color: Color) { self.update(area, &|cell,_,_|{cell.set_bg(color);}) }
         pub fn fill_fg   (&mut self, area: XYWH<u16>, color: Color) { self.update(area, &|cell,_,_|{cell.set_fg(color);}) }
@@ -1044,7 +1104,7 @@ mod xywh {
             }
         }
         pub fn tint_all (&mut self, fg: Color, bg: Color, modifier: Modifier) {
-            for cell in self.buffer.content.iter_mut() {
+            for cell in self.buffer.write().unwrap().content.iter_mut() {
                 cell.fg = fg;
                 cell.bg = bg;
                 cell.modifier = modifier;
@@ -1052,8 +1112,8 @@ mod xywh {
         }
         pub fn blit (&mut self, text: &impl AsRef<str>, x: u16, y: u16, style: Option<Style>) {
             let text = text.as_ref();
-            let buf = &mut self.buffer;
             let style = style.unwrap_or(Style::default());
+            let mut buf = self.buffer.write().unwrap();
             if x < buf.area.width && y < buf.area.height {
                 buf.set_string(x, y, text, style);
             }
@@ -1063,7 +1123,7 @@ mod xywh {
         /// TODO: do a paragraph (handle newlines)
         pub fn text (&mut self, text: &impl AsRef<str>, x0: u16, y: u16, max_width: u16) {
             let text = text.as_ref();
-            let buf  = &mut self.buffer;
+            let mut buf = &mut self.buffer;
             let mut string_width: u16 = 0;
             for character in text.chars() {
                 let x = x0 + string_width;
@@ -1072,7 +1132,7 @@ mod xywh {
                 if string_width > max_width {
                     break
                 }
-                if let Some(cell) = buf.cell_mut(ratatui::prelude::Position { x, y }) {
+                if let Some(cell) = buf.write().unwrap().cell_mut(ratatui::prelude::Position { x, y }) {
                     cell.set_char(character);
                 } else {
                     break
@@ -1098,9 +1158,7 @@ mod xywh {
         }
     }
 
-    pub fn tui_setup <W: Write> (
-        backend: &mut CrosstermBackend<W>
-    ) -> Usually<()> {
+    pub fn tui_setup <W: Write> (backend: &mut CrosstermBackend<W>) -> Usually<()> {
         let better_panic_handler = Settings::auto().verbosity(Verbosity::Full).create_panic_handler();
         std::panic::set_hook(Box::new(move |info: &std::panic::PanicHookInfo|{
             stdout().execute(LeaveAlternateScreen).unwrap();
@@ -1159,82 +1217,66 @@ mod xywh {
         }
     }
 
-    /// Spawn the output thread.
-    pub fn tui_output <T: Draw<TuiOut> + Send + Sync + 'static> (
-        engine: Arc<RwLock<Tui>>, state: &Arc<RwLock<T>>, timer: Duration
-    ) -> Result<JoinHandle<()>, std::io::Error> {
-        let exited = engine.read().unwrap().exited.clone();
-        let engine = engine.clone();
-        let state  = state.clone();
-        let Size { width, height } = engine.read().unwrap().backend.size().expect("get size failed");
-        let mut buffer = Buffer::empty(Rect { x: 0, y: 0, width, height });
-        std::thread::Builder::new()
-            .name("tui output thread".into())
-            .spawn(move || loop {
-                if exited.fetch_and(true, Relaxed) {
-                    break
-                }
-                let t0 = engine.read().unwrap().perf.get_t0();
-                let Size { width, height } = engine.read().unwrap().backend.size()
-                    .expect("get size failed");
-                if let Ok(state) = state.try_read() {
-                    let size = Rect { x: 0, y: 0, width, height };
-                    if buffer.area != size {
-                        engine.write().unwrap().backend.clear_region(ClearType::All).expect("clear failed");
-                        buffer.resize(size);
-                        buffer.reset();
+    impl TuiThread {
+        /// Spawn a TUI thread that runs `callt least one, then repeats until `exit`.
+        pub fn new <F> (exit: Arc<AtomicBool>, call: F) -> Result<Self, std::io::Error>
+            where F: Fn(&PerfModel)->() + Send + Sync + 'static
+        {
+            let perf = Arc::new(PerfModel::default());
+            Ok(Self {
+                exit: exit.clone(),
+                perf: perf.clone(),
+                join: std::thread::Builder::new().name("tengri tui output".into()).spawn(move || {
+                    while !exit.fetch_and(true, Relaxed) {
+                        let _ = perf.cycle(&call);
                     }
-                    let mut output = TuiOut { buffer, area: XYWH(0, 0, width, height) };
-                    state.draw(&mut output);
-                    buffer = engine.write().unwrap().flip(output.buffer, size);
-                }
-                let t1 = (*engine.read().unwrap()).perf.get_t1(t0).unwrap();
-                buffer.set_string(0, 0, &format!("{:>3}.{:>3}ms", t1.as_millis(), t1.as_micros() % 1000), Style::default());
-                std::thread::sleep(timer);
+                })?.into()
             })
+        }
+
+        /// Spawn a TUI thread that runs `callt least one, then repeats
+        /// until `exit`, sleeping for `time` msec after every iteration.
+        pub fn new_sleep <F> (
+            exit: Arc<AtomicBool>, time: Duration, call: F
+        ) -> Result<Self, std::io::Error>
+            where F: Fn(&PerfModel)->() + Send + Sync + 'static
+        {
+            Self::new(exit, move |perf| { let _ = call(perf); std::thread::sleep(time); })
+        }
+
+        /// Spawn a TUI thread that runs `callt least one, then repeats
+        /// until `exit`, using polling to run every `time` msec.
+        pub fn new_poll <F> (
+            exit: Arc<AtomicBool>, time: Duration, call: F
+        ) -> Result<Self, std::io::Error>
+            where F: Fn(&PerfModel)->() + Send + Sync + 'static
+        {
+            Self::new(exit, move |perf| { if poll(time).is_ok() { let _ = call(perf); } })
+        }
+
+        pub fn join (self) -> Result<(), Box<dyn std::any::Any + Send>> {
+            self.join.join()
+        }
     }
 
-    /// Spawn the input thread.
-    pub fn tui_input <T: Handle<TuiIn> + Send + Sync + 'static> (
-        engine: Arc<RwLock<Tui>>, state: &Arc<RwLock<T>>, timer: Duration
-    ) -> JoinHandle<()> {
-        let exited = engine.read().unwrap().exited.clone();
-        let state  = state.clone();
-        spawn(move || loop {
-            if exited.fetch_and(true, Relaxed) {
-                break
-            }
-            if poll(timer).is_ok() {
-                let event = read().unwrap();
-                match event {
-                    Event::Key(KeyEvent {
-                        code:      KeyCode::Char('c'),
-                        modifiers: KeyModifiers::CONTROL,
-                        kind:      KeyEventKind::Press,
-                        state:     KeyEventState::NONE
-                    }) => {
-                        exited.store(true, Relaxed);
-                    },
-                    _ => {
-                        let exited = exited.clone();
-                        let event  = TuiEvent::from_crossterm(event);
-                        if let Err(e) = state.write().unwrap().handle(&TuiIn { exited, event }) {
-                            panic!("{e}")
-                        }
-                    }
-                }
-            }
-        })
+    impl PerfModel {
+        fn cycle <F: Fn(&Self)->T, T> (&self, call: &F) -> T {
+            let t0 = self.get_t0();
+            let result = call(self);
+            let _t1 = self.get_t1(t0).unwrap();
+            result
+        }
     }
+
     impl<T> Phat<T> {
         pub const LO: &'static str = "▄";
         pub const HI: &'static str = "▀";
         /// A phat line
-        pub fn lo (fg: Color, bg: Color) -> impl Content<TuiOut> {
+        pub fn lo (fg: Color, bg: Color) -> impl Content<Tui> {
             Fixed::Y(1, Tui::fg_bg(fg, bg, Repeat::X(Self::LO)))
         }
         /// A phat line
-        pub fn hi (fg: Color, bg: Color) -> impl Content<TuiOut> {
+        pub fn hi (fg: Color, bg: Color) -> impl Content<Tui> {
             Fixed::Y(1, Tui::fg_bg(fg, bg, Repeat::X(Self::HI)))
         }
     }
@@ -1244,17 +1286,17 @@ mod xywh {
         const ICON_DEC_H: &[char] = &[' ', '🞀', ' '];
         const ICON_INC_H: &[char] = &[' ', '🞂', ' '];
     }
-    impl<S: BorderStyle, W: Content<TuiOut>> HasContent<TuiOut> for Bordered<S, W> {
-        fn content (&self) -> impl Content<TuiOut> {
+    impl<S: BorderStyle, W: Content<Tui>> HasContent<Tui> for Bordered<S, W> {
+        fn content (&self) -> impl Content<Tui> {
             Fill::XY(lay!( When::new(self.0, Border(self.0, self.1)), Pad::XY(1, 1, &self.2) ))
         }
     }
     impl<
-        A: Content<TuiOut>,
-        B: Content<TuiOut>,
-        C: Content<TuiOut>,
-    > HasContent<TuiOut> for Tryptich<A, B, C> {
-        fn content (&self) -> impl Content<TuiOut> {
+        A: Content<Tui>,
+        B: Content<Tui>,
+        C: Content<Tui>,
+    > HasContent<Tui> for Tryptich<A, B, C> {
+        fn content (&self) -> impl Content<Tui> {
             let Self { top, h, left: (w_a, ref a), middle: (w_b, ref b), right: (w_c, ref c) } = *self;
             Fixed::Y(h, if top {
                 Bsp::a(
@@ -1275,8 +1317,8 @@ mod xywh {
             })
         }
     }
-    impl<T: Content<TuiOut>> HasContent<TuiOut> for Phat<T> {
-        fn content (&self) -> impl Content<TuiOut> {
+    impl<T: Content<Tui>> HasContent<Tui> for Phat<T> {
+        fn content (&self) -> impl Content<Tui> {
             let [fg, bg, hi, lo] = self.colors;
             let top = Fixed::Y(1, Self::lo(bg, hi));
             let low = Fixed::Y(1, Self::hi(bg, lo));
@@ -1284,37 +1326,37 @@ mod xywh {
             Min::XY(self.width, self.height, Bsp::s(top, Bsp::n(low, Fill::XY(content))))
         }
     }
-    impl<T: Content<TuiOut>> Layout<TuiOut> for Modify<T> {}
-    impl<T: Content<TuiOut>> Layout<TuiOut> for Styled<T> {}
-    impl Layout<TuiOut> for Repeat<'_> {}
-    impl Layout<TuiOut> for &str {
+    impl<T: Content<Tui>> Layout<Tui> for Modify<T> {}
+    impl<T: Content<Tui>> Layout<Tui> for Styled<T> {}
+    impl Layout<Tui> for Repeat<'_> {}
+    impl Layout<Tui> for &str {
         fn layout (&self, to: XYWH<u16>) -> XYWH<u16> {
             to.centered_xy([width_chars_max(to.w(), self), 1])
         }
     }
-    impl Layout<TuiOut> for String {
+    impl Layout<Tui> for String {
         fn layout (&self, to: XYWH<u16>) -> XYWH<u16> {
             self.as_str().layout(to)
         }
     }
-    impl Layout<TuiOut> for Arc<str> {
+    impl Layout<Tui> for Arc<str> {
         fn layout (&self, to: XYWH<u16>) -> XYWH<u16> {
             self.as_ref().layout(to)
         }
     }
-    impl<'a, T: AsRef<str>> Layout<TuiOut> for TrimString<T> {
+    impl<'a, T: AsRef<str>> Layout<Tui> for TrimString<T> {
         fn layout (&self, to: XYWH<u16>) -> XYWH<u16> {
             Layout::layout(&self.as_ref(), to)
         }
     }
-    impl<'a, T: AsRef<str>> Layout<TuiOut> for TrimStringRef<'a, T> {
+    impl<'a, T: AsRef<str>> Layout<Tui> for TrimStringRef<'a, T> {
         fn layout (&self, to: XYWH<u16>) -> XYWH<u16> {
             XYWH(to.x(), to.y(), to.w().min(self.0).min(self.1.as_ref().width() as u16), to.h())
         }
     }
-    impl<T: Draw<TuiOut>> Draw<TuiOut> for ErrorBoundary<TuiOut, T> {
-        fn draw (&self, to: &mut TuiOut) {
-            match self.1.as_ref() {
+    impl<T: Draw<Tui>> Draw<Tui> for ErrorBoundary<Tui, T> {
+        fn draw (&self, to: &mut Tui) {
+            match self.0.as_ref() {
                 Ok(Some(content)) => content.draw(to),
                 Ok(None) => to.blit(&"empty?", 0, 0, Some(Style::default().yellow())),
                 Err(e) => {
@@ -1328,32 +1370,33 @@ mod xywh {
         }
     }
 
-    impl Draw<TuiOut> for u64 {
-        fn draw (&self, _to: &mut TuiOut) {
+    impl Draw<Tui> for u64 {
+        fn draw (&self, _to: &mut Tui) {
             todo!()
         }
     }
 
-    impl Draw<TuiOut> for f64 {
-        fn draw (&self, _to: &mut TuiOut) {
+    impl Draw<Tui> for f64 {
+        fn draw (&self, _to: &mut Tui) {
             todo!()
         }
     }
 
-    impl Draw<TuiOut> for Repeat<'_> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl Draw<Tui> for Repeat<'_> {
+        fn draw (&self, to: &mut Tui) {
             let XYWH(x, y, w, h) = to.area();
+            let mut buf = to.buffer.write().unwrap();
             match self {
                 Self::X(c) => {
                     for x in x..x+w {
-                        if let Some(cell) = to.buffer.cell_mut(Position::from((x, y))) {
+                        if let Some(cell) = buf.cell_mut(Position::from((x, y))) {
                             cell.set_symbol(&c);
                         }
                     }
                 },
                 Self::Y(c) => {
                     for y in y..y+h {
-                        if let Some(cell) = to.buffer.cell_mut(Position::from((x, y))) {
+                        if let Some(cell) = buf.cell_mut(Position::from((x, y))) {
                             cell.set_symbol(&c);
                         }
                     }
@@ -1362,7 +1405,7 @@ mod xywh {
                     let a = c.len();
                     for (_v, y) in (y..y+h).enumerate() {
                         for (u, x) in (x..x+w).enumerate() {
-                            if let Some(cell) = to.buffer.cell_mut(Position::from((x, y))) {
+                            if let Some(cell) = buf.cell_mut(Position::from((x, y))) {
                                 let u = u % a;
                                 cell.set_symbol(&c[u..u+1]);
                             }
@@ -1373,14 +1416,15 @@ mod xywh {
         }
     }
 
-    impl Draw<TuiOut> for Scrollbar {
-        fn draw (&self, to: &mut TuiOut) {
+    impl Draw<Tui> for Scrollbar {
+        fn draw (&self, to: &mut Tui) {
             let XYWH(x1, y1, w, h) = to.area();
+            let mut buf = to.buffer.write().unwrap();
             match self {
                 Self::X { .. } => {
                     let x2 = x1 + w;
                     for (i, x) in (x1..=x2).enumerate() {
-                        if let Some(cell) = to.buffer.cell_mut(Position::from((x, y1))) {
+                        if let Some(cell) = buf.cell_mut(Position::from((x, y1))) {
                             if i < (Self::ICON_DEC_H.len()) {
                                 cell.set_fg(Rgb(255, 255, 255));
                                 cell.set_bg(Rgb(0, 0, 0));
@@ -1404,7 +1448,7 @@ mod xywh {
                 Self::Y { .. } => {
                     let y2 = y1 + h;
                     for (i, y) in (y1..=y2).enumerate() {
-                        if let Some(cell) = to.buffer.cell_mut(Position::from((x1, y))) {
+                        if let Some(cell) = buf.cell_mut(Position::from((x1, y))) {
                             if (i as usize) < (Self::ICON_DEC_V.len()) {
                                 cell.set_fg(Rgb(255, 255, 255));
                                 cell.set_bg(Rgb(0, 0, 0));
@@ -1429,55 +1473,55 @@ mod xywh {
         }
     }
 
-    impl Draw<TuiOut> for &str {
-        fn draw (&self, to: &mut TuiOut) {
+    impl Draw<Tui> for &str {
+        fn draw (&self, to: &mut Tui) {
             let XYWH(x, y, w, ..) = self.layout(to.area());
             to.text(&self, x, y, w)
         }
     }
 
-    impl Draw<TuiOut> for String {
-        fn draw (&self, to: &mut TuiOut) {
+    impl Draw<Tui> for String {
+        fn draw (&self, to: &mut Tui) {
             self.as_str().draw(to)
         }
     }
 
-    impl Draw<TuiOut> for Arc<str> {
-        fn draw (&self, to: &mut TuiOut) { self.as_ref().draw(to) }
+    impl Draw<Tui> for Arc<str> {
+        fn draw (&self, to: &mut Tui) { self.as_ref().draw(to) }
     }
 
-    impl<T: Content<TuiOut>> Draw<TuiOut> for Foreground<Color, T> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl<T: Content<Tui>> Draw<Tui> for Foreground<Color, T> {
+        fn draw (&self, to: &mut Tui) {
             let area = self.layout(to.area());
             to.fill_fg(area, self.0);
             to.place_at(area, &self.1);
         }
     }
 
-    impl<T: Content<TuiOut>> Draw<TuiOut> for Background<Color, T> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl<T: Content<Tui>> Draw<Tui> for Background<Color, T> {
+        fn draw (&self, to: &mut Tui) {
             let area = self.layout(to.area());
             to.fill_bg(area, self.0);
             to.place_at(area, &self.1);
         }
     }
 
-    impl<T: Content<TuiOut>> Draw<TuiOut> for Modify<T> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl<T: Content<Tui>> Draw<Tui> for Modify<T> {
+        fn draw (&self, to: &mut Tui) {
             to.fill_mod(to.area(), self.0, self.1);
             self.2.draw(to)
         }
     }
 
-    impl<T: Content<TuiOut>> Draw<TuiOut> for Styled<T> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl<T: Content<Tui>> Draw<Tui> for Styled<T> {
+        fn draw (&self, to: &mut Tui) {
             to.place(&self.1);
             // TODO write style over area
         }
     }
 
-    impl<S: BorderStyle> Draw<TuiOut> for Border<S> {
-        fn draw (&self, to: &mut TuiOut) {
+    impl<S: BorderStyle> Draw<Tui> for Border<S> {
+        fn draw (&self, to: &mut Tui) {
             let Border(enabled, style) = self;
             if *enabled {
                 let area = to.area();
@@ -1499,20 +1543,21 @@ mod xywh {
         }
     }
 
-    impl<'a, T: AsRef<str>> Draw<TuiOut> for TrimString<T> {
-        fn draw (&self, to: &mut TuiOut) { Draw::draw(&self.as_ref(), to) }
+    impl<'a, T: AsRef<str>> Draw<Tui> for TrimString<T> {
+        fn draw (&self, to: &mut Tui) { Draw::draw(&self.as_ref(), to) }
     }
 
-    impl<T: AsRef<str>> Draw<TuiOut> for TrimStringRef<'_, T> {
-        fn draw (&self, target: &mut TuiOut) {
+    impl<T: AsRef<str>> Draw<Tui> for TrimStringRef<'_, T> {
+        fn draw (&self, target: &mut Tui) {
             let area = target.area();
+            let mut buf = target.buffer.write().unwrap();
             let mut width: u16 = 1;
             let mut chars = self.1.as_ref().chars();
             while let Some(c) = chars.next() {
                 if width > self.0 || width > area.w() {
                     break
                 }
-                if let Some(cell) = target.buffer.cell_mut(Position {
+                if let Some(cell) = buf.cell_mut(Position {
                     x: area.x() + width - 1,
                     y: area.y()
                 }) {
@@ -1581,7 +1626,7 @@ mod xywh {
             "bropen"  | "openbracket"  => Char('['),
             "brclose" | "closebracket" => Char(']'),
             "pgup" | "pageup"   => PageUp,
-            "pgdn" | "pagedown" => PageDown, 
+            "pgdn" | "pagedown" => PageDown,
             "f1"                => F(1),
             "f2"                => F(2),
             "f3"                => F(3),
@@ -1625,16 +1670,16 @@ mod xywh {
     /// Should be impl something or other...
     ///
     /// ```
-    /// use tengri::{Namespace, Understand, TuiOut, ratatui::prelude::Color};
+    /// use tengri::{Namespace, Understand, Tui, ratatui::prelude::Color};
     ///
     /// struct State;
     /// impl<'b> Namespace<'b, bool>    for State {}
     /// impl<'b> Namespace<'b, u16>     for State {}
     /// impl<'b> Namespace<'b, Color>   for State {}
-    /// impl     Understand<TuiOut, ()> for State {}
+    /// impl     Understand<Tui, ()> for State {}
     /// # fn main () -> tengri::Usually<()> {
     /// let state = State;
-    /// let mut out = TuiOut::default();
+    /// let mut out = Tui::default();
     /// tengri::evaluate_output_expression_tui(&state, &mut out, "")?;
     /// tengri::evaluate_output_expression_tui(&state, &mut out, "text Hello world!")?;
     /// tengri::evaluate_output_expression_tui(&state, &mut out, "fg (g 0) (text Hello world!)")?;
@@ -1643,9 +1688,9 @@ mod xywh {
     /// # Ok(()) }
     /// ```
     pub fn evaluate_output_expression_tui <'a, S> (
-        state: &S, output: &mut TuiOut, expr: impl Expression + 'a
+        state: &S, output: &mut Tui, expr: impl Expression + 'a
     ) -> Usually<bool> where
-        S: Understand<TuiOut, ()>
+        S: Understand<Tui, ()>
             + for<'b>Namespace<'b, bool>
             + for<'b>Namespace<'b, u16>
             + for<'b>Namespace<'b, Color>
@@ -1668,7 +1713,7 @@ mod xywh {
             Some("fg") => {
                 let arg0  = arg0?.expect("fg: expected arg 0 (color)");
                 let color = Namespace::namespace(state, arg0)?.unwrap_or_else(||panic!("fg: {arg0:?}: not a color"));
-                let thunk = Thunk::new(move|output: &mut TuiOut|state.understand(output, &arg1).unwrap());
+                let thunk = Thunk::new(move|output: &mut Tui|state.understand(output, &arg1).unwrap());
                 output.place(&Tui::fg(color, thunk))
             },
 
@@ -1678,7 +1723,7 @@ mod xywh {
                 //panic!("head: {head:?}\narg0: {arg0:?}\narg1: {arg1:?}\narg2: {arg2:?}");
                 let arg0  = arg0?.expect("bg: expected arg 0 (color)");
                 let color = Namespace::namespace(state, arg0)?.unwrap_or_else(||panic!("bg: {arg0:?}: not a color"));
-                let thunk = Thunk::new(move|output: &mut TuiOut|state.understand(output, &arg1).unwrap());
+                let thunk = Thunk::new(move|output: &mut Tui|state.understand(output, &arg1).unwrap());
                 output.place(&Tui::bg(color, thunk))
             },
 
@@ -1692,7 +1737,7 @@ mod xywh {
     /// let _ = tengri::button_2("", "", true);
     /// let _ = tengri::button_2("", "", false);
     /// ```
-    pub fn button_2 <'a> (key: impl Content<TuiOut>, label: impl Content<TuiOut>, editing: bool) -> impl Content<TuiOut> {
+    pub fn button_2 <'a> (key: impl Content<Tui>, label: impl Content<Tui>, editing: bool) -> impl Content<Tui> {
         Tui::bold(true, Bsp::e(
             Tui::fg_bg(Tui::orange(), Tui::g(0), Bsp::e(Tui::fg(Tui::g(0), &"▐"), Bsp::e(key, Tui::fg(Tui::g(96), &"▐")))),
             When::new(!editing, Tui::fg_bg(Tui::g(255), Tui::g(96), label))))
@@ -1703,8 +1748,8 @@ mod xywh {
     /// let _ = tengri::button_3("", "", "", false);
     /// ```
     pub fn button_3 <'a> (
-        key: impl Content<TuiOut>, label: impl Content<TuiOut>, value: impl Content<TuiOut>, editing: bool,
-    ) -> impl Content<TuiOut> {
+        key: impl Content<Tui>, label: impl Content<Tui>, value: impl Content<Tui>, editing: bool,
+    ) -> impl Content<Tui> {
         Tui::bold(true, Bsp::e(
             Tui::fg_bg(Tui::orange(), Tui::g(0),
                 Bsp::e(Tui::fg(Tui::g(0), &"▐"), Bsp::e(key, Tui::fg(if editing { Tui::g(128) } else { Tui::g(96) }, "▐")))),
@@ -1731,9 +1776,9 @@ mod xywh {
                 fn enabled (&self) -> bool { self.0 }
             }
             #[derive(Copy, Clone)] pub struct $T(pub bool, pub Style);
-            impl Layout<TuiOut> for $T {}
-            impl Draw<TuiOut> for $T {
-                fn draw (&self, to: &mut TuiOut) {
+            impl Layout<Tui> for $T {}
+            impl Draw<Tui> for $T {
+                fn draw (&self, to: &mut Tui) {
                     if self.enabled() { let _ = BorderStyle::draw(self, to); }
                 }
             }
diff --git a/src/tengri_struct.rs b/src/tengri_struct.rs
index 5460d64..8dd33e3 100644
--- a/src/tengri_struct.rs
+++ b/src/tengri_struct.rs
@@ -2,56 +2,51 @@ pub use self::logical::*; mod logical {
     use crate::*;
 
     /// Thunks can be natural error boundaries!
+    ///
+    /// ```
+    /// let _ = tengri::ErrorBoundary::<tengri::Tui, &'static str>::new(Ok(Some("hello")));
+    /// let _ = tengri::ErrorBoundary::<tengri::Tui, &'static str>::new(Ok(None));
+    /// let _ = tengri::ErrorBoundary::<tengri::Tui, &'static str>::new(Err("draw fail".into()));
+    /// ```
     pub struct ErrorBoundary<O: Out, T: Draw<O>>(
-        pub std::marker::PhantomData<O>,
-        pub Perhaps<T>
-    );
-
-    // TODO DOCUMENTME
-    pub struct Lazy<O, T, F>(
-        pub F,
-        pub PhantomData<(O, T)>
-    );
-
-    // TODO DOCUMENTME
-    pub struct Thunk<O: Out, F: Fn(&mut O)>(
+        pub Perhaps<T>,
         pub PhantomData<O>,
-        pub F
     );
 
-    // TODO DOCUMENTME
+    /// Late-evaluate a rendering.
+    ///
+    /// ```
+    /// let _ = tengri::Thunk::<tengri::Tui, _>::new(|out|{});
+    /// ```
+    pub struct Thunk<O: Out, F: Fn(&mut O)>(
+        pub F,
+        pub PhantomData<O>,
+    );
+
+    /// Memoize a rendering.
+    ///
+    /// ```
+    /// let _ = tengri::Memo::new((), ());
+    /// ```
     #[derive(Debug, Default)] pub struct Memo<T, U> {
         pub value: T,
         pub view: Arc<RwLock<U>>
     }
 }
 
-pub use self::temporal::*; mod temporal {
-    use crate::*;
-
-    /// Performance counter
-    #[derive(Debug)]
-    pub struct PerfModel {
-        pub enabled: bool,
-
-        pub clock:  quanta::Clock,
-        // In nanoseconds. Time used by last iteration.
-        pub used:   AtomicF64,
-        // In microseconds. Max prescribed time for iteration (frame, chunk...).
-        pub window: AtomicF64,
-    }
-}
-
 pub use self::spatial::*; mod spatial {
     use crate::*;
 
-    // TODO DOCUMENTME
-    pub struct Bordered<S, W>(pub bool, pub S, pub W);
-
-    // TODO DOCUMENTME
-    pub struct Border<S>(pub bool, pub S);
-
     /// A binary split or layer.
+    ///
+    /// ```
+    /// let _ = tengri::Bsp::n((), ());
+    /// let _ = tengri::Bsp::s((), ());
+    /// let _ = tengri::Bsp::e((), ());
+    /// let _ = tengri::Bsp::w((), ());
+    /// let _ = tengri::Bsp::a((), ());
+    /// let _ = tengri::Bsp::b((), ());
+    /// ```
     pub struct Bsp<Head, Tail>(
         /// Direction of split
         pub(crate) Direction,
@@ -118,7 +113,7 @@ pub use self::spatial::*; mod spatial {
     /// A widget that tracks its rendered width and height.
     ///
     /// ```
-    /// let measure = tengri::Measure::<tengri::TuiOut>::default();
+    /// let measure = tengri::Measure::<tengri::Tui>::default();
     /// ```
     #[derive(Default)] pub struct Measure<O: Out> {
         pub __: PhantomData<O>,
@@ -129,7 +124,7 @@ pub use self::spatial::*; mod spatial {
     /// Show an item only when a condition is true.
     ///
     /// ```
-    /// fn test () -> impl tengri::Draw<tengri::TuiOut> {
+    /// fn test () -> impl tengri::Draw<tengri::Tui> {
     ///     tengri::when(true, "Yes")
     /// }
     /// ```
@@ -141,7 +136,7 @@ pub use self::spatial::*; mod spatial {
     /// Show one item if a condition is true and another if the condition is false.
     ///
     /// ```
-    /// fn test () -> impl tengri::Draw<tengri::TuiOut> {
+    /// fn test () -> impl tengri::Draw<tengri::Tui> {
     ///     tengri::either(true, "Yes", "No")
     /// }
     /// ```
@@ -212,7 +207,7 @@ pub use self::spatial::*; mod spatial {
     /// ```
     /// use ::tengri::*;
     /// let area = XYWH(10u16, 10, 20, 20);
-    /// fn test (area: XYWH<u16>, item: &impl Draw<TuiOut>, expected: [u16;4]) {
+    /// fn test (area: XYWH<u16>, item: &impl Draw<Tui>, expected: [u16;4]) {
     ///     //assert_eq!(Lay::layout(item, area), expected);
     ///     //assert_eq!(Draw::layout(item, area),  expected);
     /// };
@@ -242,13 +237,19 @@ pub use self::spatial::*; mod spatial {
     // TODO DOCUMENTME
     pub enum Pad<U, A> { X(U, A), Y(U, A), XY(U, U, A), }
 
+    // TODO DOCUMENTME
+    pub struct Bordered<S, W>(pub bool, pub S, pub W);
+
+    // TODO DOCUMENTME
+    pub struct Border<S>(pub bool, pub S);
+
     /// TODO DOCUMENTME
     ///
     /// ```
     /// use tengri::{Bounded, XYWH};
     /// let area = XYWH(0, 0, 0, 0);
     /// let content = "";
-    /// let bounded: Bounded<tengri::TuiOut, _> = Bounded(area, content);
+    /// let bounded: Bounded<tengri::Tui, _> = Bounded(area, content);
     /// ```
     pub struct Bounded<O: Out, D>(pub XYWH<O::Unit>, pub D);
 
@@ -314,24 +315,26 @@ pub use self::spatial::*; mod spatial {
     /// # Ok(()) }
     /// ```
     pub struct Tui {
+        /// Exit flag
         pub exited:  Arc<AtomicBool>,
-        pub backend: CrosstermBackend<Box<dyn Write + Send + Sync>>,
-        pub buffer:  Buffer,
-        pub area:    [u16;4],
+        /// Error message
+        pub error:   Option<Arc<str>>,
+        /// Performance counter
         pub perf:    PerfModel,
+        /// Ratatui backend
+        pub backend: RwLock<CrosstermBackend<Box<dyn Write + Send + Sync>>>,
+        /// Current tnput event
+        pub event:   Option<TuiEvent>,
+        /// Current output buffer
+        pub buffer:  RwLock<Buffer>,
+        /// FIXME unused?
+        pub area:    XYWH<u16>,
     }
 
-    /// The TUI input event source.
-    ///
-    /// ```
-    /// use ::{tengri::{TuiIn, TuiEvent}, std::sync::Arc};
-    /// let tui_in = TuiIn { event: 'f'.into(), exited: Arc::new(false.into()) };
-    /// ```
-    #[derive(Debug, Clone)] pub struct TuiIn {
-        /// Input event
-        pub event: TuiEvent,
-        /// Exit flag
-        pub exited: Arc<AtomicBool>,
+    #[derive(Debug)] pub struct TuiThread {
+        pub exit: Arc<AtomicBool>,
+        pub perf: Arc<PerfModel>,
+        pub join: JoinHandle<()>,
     }
 
     #[derive(Debug, Clone, Eq, PartialEq, PartialOrd)] pub struct TuiEvent(
@@ -343,16 +346,6 @@ pub use self::spatial::*; mod spatial {
         pub KeyModifiers
     );
 
-    /// The TUI output render target.
-    ///
-    /// ```
-    /// let tui_out = tengri::TuiOut::default();
-    /// ```
-    #[derive(Default)] pub struct TuiOut {
-        pub buffer: Buffer,
-        pub area:   XYWH<u16>,
-    }
-
     /// TUI buffer sized by `usize` instead of `u16`.
     #[derive(Default)] pub struct BigBuffer {
         pub width:   usize,
@@ -499,3 +492,19 @@ mod textual {
     pub type BoxedJackEventHandler<'j> =
         Box<dyn Fn(JackEvent) + Send + Sync + 'j>;
 }
+
+pub use self::temporal::*; mod temporal {
+    use crate::*;
+
+    /// Performance counter
+    #[derive(Debug)]
+    pub struct PerfModel {
+        pub clock: quanta::Clock,
+        /// Measurement has a small cost. Disable it here.
+        pub enabled: bool,
+        // In nanoseconds. Time used by last iteration.
+        pub used: AtomicF64,
+        // In microseconds. Max prescribed time for iteration (frame, chunk...).
+        pub window: AtomicF64,
+    }
+}
diff --git a/src/tengri_trait.rs b/src/tengri_trait.rs
index f5e80f0..052225b 100644
--- a/src/tengri_trait.rs
+++ b/src/tengri_trait.rs
@@ -235,20 +235,20 @@ pub use self::output::*; mod output {
 #[cfg(feature = "tui")] mod tui {
     use crate::*;
     use ratatui::prelude::*;
-    pub trait TuiDraw    = Draw<TuiOut>;
-    pub trait TuiLayout  = crate::Layout<TuiOut>;
-    pub trait TuiContent = Content<TuiOut>;
-    pub trait TuiHandle  = Handle<TuiIn>;
+    pub trait TuiDraw    = Draw<Tui>;
+    pub trait TuiLayout  = crate::Layout<Tui>;
+    pub trait TuiContent = Content<Tui>;
+    pub trait TuiHandle  = Handle<Tui>;
     pub trait TuiWidget  = TuiDraw + TuiHandle;
-    pub trait BorderStyle: Content<TuiOut> + Copy {
+    pub trait BorderStyle: Content<Tui> + Copy {
         fn enabled (&self) -> bool;
-        fn enclose (self, w: impl Content<TuiOut>) -> impl Content<TuiOut> {
+        fn enclose (self, w: impl Content<Tui>) -> impl Content<Tui> {
             Bsp::b(Fill::XY(Border(self.enabled(), self)), w)
         }
-        fn enclose2 (self, w: impl Content<TuiOut>) -> impl Content<TuiOut> {
+        fn enclose2 (self, w: impl Content<Tui>) -> impl Content<Tui> {
             Bsp::b(Pad::XY(1, 1, Fill::XY(Border(self.enabled(), self))), w)
         }
-        fn enclose_bg (self, w: impl Content<TuiOut>) -> impl Content<TuiOut> {
+        fn enclose_bg (self, w: impl Content<Tui>) -> impl Content<Tui> {
             Tui::bg(self.style().unwrap().bg.unwrap_or(Color::Reset),
                 Bsp::b(Fill::XY(Border(self.enabled(), self)), w))
         }
@@ -275,7 +275,7 @@ pub use self::output::*; mod output {
         fn border_sw (&self) -> &str { Self::SW }
         fn border_se (&self) -> &str { Self::SE }
         #[inline] fn draw <'a> (
-            &self, to: &mut TuiOut
+            &self, to: &mut Tui
         ) -> Usually<()> {
             if self.enabled() {
                 self.draw_horizontal(to, None)?;
@@ -285,7 +285,7 @@ pub use self::output::*; mod output {
             Ok(())
         }
         #[inline] fn draw_horizontal (
-            &self, to: &mut TuiOut, style: Option<Style>
+            &self, to: &mut Tui, style: Option<Style>
         ) -> Usually<XYWH<u16>> {
             let area = to.area();
             let style = style.or_else(||self.style_horizontal());
@@ -297,7 +297,7 @@ pub use self::output::*; mod output {
             Ok(area)
         }
         #[inline] fn draw_vertical (
-            &self, to: &mut TuiOut, style: Option<Style>
+            &self, to: &mut Tui, style: Option<Style>
         ) -> Usually<XYWH<u16>> {
             let area = to.area();
             let style = style.or_else(||self.style_vertical());
@@ -315,7 +315,7 @@ pub use self::output::*; mod output {
             Ok(area)
         }
         #[inline] fn draw_corners (
-            &self, to: &mut TuiOut, style: Option<Style>
+            &self, to: &mut Tui, style: Option<Style>
         ) -> Usually<XYWH<u16>> {
             let area = to.area();
             let style = style.or_else(||self.style_corners());