From 905486edbd4702c6337d3f2460de13e8b2ae3888 Mon Sep 17 00:00:00 2001
From: unspeaker <hora.nqma@protonmail.com>
Date: Sun, 5 Jan 2025 08:16:15 +0100
Subject: [PATCH] break down engine modules

---
 edn/src/edn_item.rs             |  46 +----------
 edn/src/edn_iter.rs             |  45 ++++++++++
 edn/src/edn_main.rs             |   2 -
 edn/src/lib.rs                  |   7 +-
 engine/src/engine.rs            | 142 +-------------------------------
 engine/src/input.rs             |  58 +------------
 engine/src/input/handle.rs      |  59 +++++++++++++
 engine/src/output.rs            |  39 ++-------
 engine/src/output/area.rs       |  84 +++++++++++++++++++
 engine/src/output/content.rs    |  17 ++++
 engine/src/output/coordinate.rs |  26 ++++++
 engine/src/output/render.rs     |  12 +++
 engine/src/output/size.rs       |  32 +++++++
 engine/src/output/thunk.rs      |  10 +++
 engine/src/tui.rs               |  74 +----------------
 engine/src/tui/tui_run.rs       |  75 +++++++++++++++++
 16 files changed, 376 insertions(+), 352 deletions(-)
 create mode 100644 edn/src/edn_iter.rs
 create mode 100644 engine/src/input/handle.rs
 create mode 100644 engine/src/output/area.rs
 create mode 100644 engine/src/output/content.rs
 create mode 100644 engine/src/output/coordinate.rs
 create mode 100644 engine/src/output/render.rs
 create mode 100644 engine/src/output/size.rs
 create mode 100644 engine/src/output/thunk.rs
 create mode 100644 engine/src/tui/tui_run.rs

diff --git a/edn/src/edn_item.rs b/edn/src/edn_item.rs
index d4af7b6b..d766f08f 100644
--- a/edn/src/edn_item.rs
+++ b/edn/src/edn_item.rs
@@ -55,52 +55,8 @@ impl<T: AsRef<str> + PartialEq + Default + Clone + std::fmt::Debug> EdnItem<T> {
         EdnIterator::new(&self)
     }
 }
-enum EdnIterator<'a, T>{
-    Nil,
-    Sym(&'a T),
-    Exp(Vec<EdnIterator<'a, T>>)
-}
-impl<'a, T: AsRef<str>> EdnIterator<'a, T> {
-    fn new (item: &'a EdnItem<T>) -> Self {
-        use EdnItem::*;
-        match item {
-            Sym(t) => Self::Sym(t),
-            Exp(i) => Self::Exp(i.iter().map(EdnIterator::new).collect()),
-            _ => Self::Nil,
-        }
-    }
-}
-impl<'a, T: AsRef<str>> Iterator for EdnIterator<'a, T> {
-    type Item = &'a T;
-    fn next (&mut self) -> Option<Self::Item> {
-        use EdnIterator::*;
-        match self {
-            Sym(t) => {
-                let t = *t;
-                *self = Nil;
-                Some(t)
-            },
-            Exp(v) => match v.as_mut_slice() {
-                [a] => if let Some(next) = a.next() {
-                    Some(next)
-                } else {
-                    *self = Exp(v.split_off(1));
-                    self.next()
-                },
-                _ => {
-                    *self = Nil;
-                    None
-                }
-            },
-            _ => {
-                *self = Nil;
-                None
-            }
-        }
-    }
-}
 impl EdnItem<String> {
-    fn from (other: EdnItem<impl AsRef<str>>) -> EdnItem<String> {
+    pub fn from (other: EdnItem<impl AsRef<str>>) -> EdnItem<String> {
         use EdnItem::*;
         match other {
             Nil => Nil,
diff --git a/edn/src/edn_iter.rs b/edn/src/edn_iter.rs
new file mode 100644
index 00000000..55409cb0
--- /dev/null
+++ b/edn/src/edn_iter.rs
@@ -0,0 +1,45 @@
+use crate::*;
+pub enum EdnIterator<'a, T>{
+    Nil,
+    Sym(&'a T),
+    Exp(Vec<EdnIterator<'a, T>>)
+}
+impl<'a, T: AsRef<str>> EdnIterator<'a, T> {
+    pub fn new (item: &'a EdnItem<T>) -> Self {
+        use EdnItem::*;
+        match item {
+            Sym(t) => Self::Sym(t),
+            Exp(i) => Self::Exp(i.iter().map(EdnIterator::new).collect()),
+            _ => Self::Nil,
+        }
+    }
+}
+impl<'a, T: AsRef<str>> Iterator for EdnIterator<'a, T> {
+    type Item = &'a T;
+    fn next (&mut self) -> Option<Self::Item> {
+        use EdnIterator::*;
+        match self {
+            Sym(t) => {
+                let t = *t;
+                *self = Nil;
+                Some(t)
+            },
+            Exp(v) => match v.as_mut_slice() {
+                [a] => if let Some(next) = a.next() {
+                    Some(next)
+                } else {
+                    *self = Exp(v.split_off(1));
+                    self.next()
+                },
+                _ => {
+                    *self = Nil;
+                    None
+                }
+            },
+            _ => {
+                *self = Nil;
+                None
+            }
+        }
+    }
+}
diff --git a/edn/src/edn_main.rs b/edn/src/edn_main.rs
index f565d808..1bd543b9 100644
--- a/edn/src/edn_main.rs
+++ b/edn/src/edn_main.rs
@@ -1,5 +1,3 @@
-use crate::*;
-
 #[macro_export] macro_rules! run_tek_edn {
     ($source:expr) => {
         struct EdnRunner;
diff --git a/edn/src/lib.rs b/edn/src/lib.rs
index 857ab98e..397cd068 100644
--- a/edn/src/lib.rs
+++ b/edn/src/lib.rs
@@ -5,16 +5,13 @@ pub(crate) use std::{
     fmt::{Debug, Formatter, Error as FormatError}
 };
 pub use ::tek_layout;
-pub(crate) use ::tek_layout::{
-    *,
-    tek_engine::{Usually, Content, Render, Engine, Thunk}
-};
 
 mod edn_error; pub use self::edn_error::*;
 mod edn_item;  pub use self::edn_item::*;
+mod edn_iter;  pub use self::edn_iter::*;
+mod edn_main;  pub use self::edn_main::*;
 mod edn_token; pub use self::edn_token::*;
 mod edn_view;  pub use self::edn_view::*;
-mod edn_main;  pub use self::edn_main::*;
 
 #[cfg(test)] #[test] fn test_edn () -> Result<(), ParseError> {
     use EdnItem::*;
diff --git a/engine/src/engine.rs b/engine/src/engine.rs
index 886f9670..b3a862cd 100644
--- a/engine/src/engine.rs
+++ b/engine/src/engine.rs
@@ -1,6 +1,4 @@
 use crate::*;
-use std::fmt::{Debug, Display};
-use std::ops::{Add, Sub, Mul, Div};
 
 /// Platform backend.
 pub trait Engine: Send + Sync + Sized {
@@ -13,9 +11,9 @@ pub trait Engine: Send + Sync + Sized {
     /// Unit of length
     type Unit: Coordinate;
     /// Rectangle without offset
-    type Size: Size<Self::Unit> + From<[Self::Unit;2]> + Debug + Copy;
+    type Size: Size<Self::Unit>;
     /// Rectangle with offset
-    type Area: Area<Self::Unit> + From<[Self::Unit;4]> + Debug + Copy;
+    type Area: Area<Self::Unit>;
     /// Prepare before run
     fn setup (&mut self) -> Usually<()> { Ok(()) }
     /// True if done
@@ -23,139 +21,3 @@ pub trait Engine: Send + Sync + Sized {
     /// Clean up after run
     fn teardown (&mut self) -> Usually<()> { Ok(()) }
 }
-
-/// A linear coordinate.
-pub trait Coordinate: Send + Sync + Copy
-    + Add<Self, Output=Self>
-    + Sub<Self, Output=Self>
-    + Mul<Self, Output=Self>
-    + Div<Self, Output=Self>
-    + Ord + PartialEq + Eq
-    + Debug + Display + Default
-    + From<u16> + Into<u16>
-    + Into<usize>
-    + Into<f64>
-{
-    #[inline] fn minus (self, other: Self) -> Self {
-        if self >= other {
-            self - other
-        } else {
-            0.into()
-        }
-    }
-    #[inline] fn zero () -> Self {
-        0.into()
-    }
-}
-
-pub trait Size<N: Coordinate> {
-    fn x (&self) -> N;
-    fn y (&self) -> N;
-    #[inline] fn w (&self) -> N { self.x() }
-    #[inline] fn h (&self) -> N { self.y() }
-    #[inline] fn wh (&self) -> [N;2] { [self.x(), self.y()] }
-    #[inline] fn clip_w (&self, w: N) -> [N;2] { [self.w().min(w), self.h()] }
-    #[inline] fn clip_h (&self, h: N) -> [N;2] { [self.w(), self.h().min(h)] }
-    #[inline] fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
-        if self.w() < w || self.h() < h {
-            Err(format!("min {w}x{h}").into())
-        } else {
-            Ok(self)
-        }
-    }
-    #[inline] fn zero () -> [N;2] {
-        [N::zero(), N::zero()]
-    }
-}
-
-impl<N: Coordinate> Size<N> for (N, N) {
-    #[inline] fn x (&self) -> N { self.0 }
-    #[inline] fn y (&self) -> N { self.1 }
-}
-
-impl<N: Coordinate> Size<N> for [N;2] {
-    #[inline] fn x (&self) -> N { self[0] }
-    #[inline] fn y (&self) -> N { self[1] }
-}
-
-pub trait Area<N: Coordinate> {
-    fn x (&self) -> N;
-    fn y (&self) -> N;
-    fn w (&self) -> N;
-    fn h (&self) -> N;
-    #[inline] fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
-        if self.w() < w || self.h() < h {
-            Err(format!("min {w}x{h}").into())
-        } else {
-            Ok(self)
-        }
-    }
-    #[inline] fn xy (&self) -> [N;2] {
-        [self.x(), self.y()]
-    }
-    #[inline] fn wh (&self) -> [N;2] {
-        [self.w(), self.h()]
-    }
-    #[inline] fn xywh (&self) -> [N;4] {
-        [self.x(), self.y(), self.w(), self.h()]
-    }
-    #[inline] fn clip_h (&self, h: N) -> [N;4] {
-        [self.x(), self.y(), self.w(), self.h().min(h)]
-    }
-    #[inline] fn clip_w (&self, w: N) -> [N;4] {
-        [self.x(), self.y(), self.w().min(w), self.h()]
-    }
-    #[inline] fn clip (&self, wh: impl Size<N>) -> [N;4] {
-        [self.x(), self.y(), wh.w(), wh.h()]
-    }
-    #[inline] fn set_w (&self, w: N) -> [N;4] {
-        [self.x(), self.y(), w, self.h()]
-    }
-    #[inline] fn set_h (&self, h: N) -> [N;4] {
-        [self.x(), self.y(), self.w(), h]
-    }
-    #[inline] fn x2 (&self) -> N {
-        self.x() + self.w()
-    }
-    #[inline] fn y2 (&self) -> N {
-        self.y() + self.h()
-    }
-    #[inline] fn lrtb (&self) -> [N;4] {
-        [self.x(), self.x2(), self.y(), self.y2()]
-    }
-    #[inline] fn center (&self) -> [N;2] {
-        [self.x() + self.w()/2.into(), self.y() + self.h()/2.into()]
-    }
-    #[inline] fn center_x (&self, n: N) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [(x + w / 2.into()).minus(n / 2.into()), y + h / 2.into(), n, 1.into()]
-    }
-    #[inline] fn center_y (&self, m: N) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [x + w / 2.into(), (y + h / 2.into()).minus(m / 2.into()), 1.into(), m]
-    }
-    #[inline] fn center_xy (&self, [n, m]: [N;2]) -> [N;4] {
-        let [x, y, w, h] = self.xywh();
-        [(x + w / 2.into()).minus(n / 2.into()), (y + h / 2.into()).minus(m / 2.into()), n, m]
-    }
-    #[inline] fn centered (&self) -> [N;2] {
-        [self.x().minus(self.w()/2.into()), self.y().minus(self.h()/2.into())]
-    }
-    fn zero () -> [N;4] {
-        [N::zero(), N::zero(), N::zero(), N::zero()]
-    }
-}
-
-impl<N: Coordinate> Area<N> for (N, N, N, N) {
-    #[inline] fn x (&self) -> N { self.0 }
-    #[inline] fn y (&self) -> N { self.1 }
-    #[inline] fn w (&self) -> N { self.2 }
-    #[inline] fn h (&self) -> N { self.3 }
-}
-
-impl<N: Coordinate> Area<N> for [N;4] {
-    #[inline] fn x (&self) -> N { self[0] }
-    #[inline] fn y (&self) -> N { self[1] }
-    #[inline] fn w (&self) -> N { self[2] }
-    #[inline] fn h (&self) -> N { self[3] }
-}
diff --git a/engine/src/input.rs b/engine/src/input.rs
index 0ec9dbf3..0cc8718a 100644
--- a/engine/src/input.rs
+++ b/engine/src/input.rs
@@ -1,12 +1,6 @@
 use crate::*;
-use std::sync::{Arc, Mutex, RwLock};
 
-/// Handle input
-pub trait Handle<E: Engine>: Send + Sync {
-    fn handle (&mut self, _input: &E::Input) -> Perhaps<E::Handled> {
-        Ok(None)
-    }
-}
+mod handle; pub use self::handle::*;
 
 /// Current input state
 pub trait Input<E: Engine> {
@@ -19,53 +13,3 @@ pub trait Input<E: Engine> {
     /// Mark component as done
     fn done (&self);
 }
-
-#[macro_export] macro_rules! handle {
-    (<$E:ty>|$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
-        impl Handle<$E> for $Struct {
-            fn handle (&mut $self, $input: &<$E as Engine>::Input) -> Perhaps<<$E as Engine>::Handled> {
-                $handler
-            }
-        }
-    }
-}
-
-impl<E: Engine, H: Handle<E>> Handle<E> for &mut H {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        (*self).handle(context)
-    }
-}
-
-impl<E: Engine, H: Handle<E>> Handle<E> for Option<H> {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        if let Some(ref mut handle) = self {
-            handle.handle(context)
-        } else {
-            Ok(None)
-        }
-    }
-}
-
-impl<H, E: Engine> Handle<E> for Mutex<H> where H: Handle<E> {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        self.get_mut().unwrap().handle(context)
-    }
-}
-
-impl<H, E: Engine> Handle<E> for Arc<Mutex<H>> where H: Handle<E> {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        self.lock().unwrap().handle(context)
-    }
-}
-
-impl<H, E: Engine> Handle<E> for RwLock<H> where H: Handle<E> {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        self.write().unwrap().handle(context)
-    }
-}
-
-impl<H, E: Engine> Handle<E> for Arc<RwLock<H>> where H: Handle<E> {
-    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
-        self.write().unwrap().handle(context)
-    }
-}
diff --git a/engine/src/input/handle.rs b/engine/src/input/handle.rs
new file mode 100644
index 00000000..15a9b5e1
--- /dev/null
+++ b/engine/src/input/handle.rs
@@ -0,0 +1,59 @@
+use crate::*;
+use std::sync::{Mutex, Arc, RwLock};
+
+/// Handle input
+pub trait Handle<E: Engine>: Send + Sync {
+    fn handle (&mut self, _input: &E::Input) -> Perhaps<E::Handled> {
+        Ok(None)
+    }
+}
+
+#[macro_export] macro_rules! handle {
+    (<$E:ty>|$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
+        impl Handle<$E> for $Struct {
+            fn handle (&mut $self, $input: &<$E as Engine>::Input) -> Perhaps<<$E as Engine>::Handled> {
+                $handler
+            }
+        }
+    }
+}
+
+impl<E: Engine, H: Handle<E>> Handle<E> for &mut H {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        (*self).handle(context)
+    }
+}
+
+impl<E: Engine, H: Handle<E>> Handle<E> for Option<H> {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        if let Some(ref mut handle) = self {
+            handle.handle(context)
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+impl<H, E: Engine> Handle<E> for Mutex<H> where H: Handle<E> {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        self.get_mut().unwrap().handle(context)
+    }
+}
+
+impl<H, E: Engine> Handle<E> for Arc<Mutex<H>> where H: Handle<E> {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        self.lock().unwrap().handle(context)
+    }
+}
+
+impl<H, E: Engine> Handle<E> for RwLock<H> where H: Handle<E> {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        self.write().unwrap().handle(context)
+    }
+}
+
+impl<H, E: Engine> Handle<E> for Arc<RwLock<H>> where H: Handle<E> {
+    fn handle (&mut self, context: &E::Input) -> Perhaps<E::Handled> {
+        self.write().unwrap().handle(context)
+    }
+}
diff --git a/engine/src/output.rs b/engine/src/output.rs
index ed3b9b8c..2e891766 100644
--- a/engine/src/output.rs
+++ b/engine/src/output.rs
@@ -1,5 +1,13 @@
 use crate::*;
-use std::marker::PhantomData;
+
+mod coordinate; pub use self::coordinate::*;
+mod size; pub use self::size::*;
+mod area; pub use self::area::*;
+
+mod render;  pub use self::render::*;
+mod content; pub use self::content::*;
+mod thunk;   pub use self::thunk::*;
+
 /// Rendering target
 pub trait Output<E: Engine> {
     /// Current output area
@@ -14,35 +22,6 @@ pub trait Output<E: Engine> {
     #[inline] fn h (&self) -> E::Unit { self.area().h() }
     #[inline] fn wh (&self) -> E::Size { self.area().wh().into() }
 }
-pub trait Render<E: Engine>: Send + Sync {
-    fn layout (&self, area: E::Area) -> E::Area;
-    fn render (&self, output: &mut E::Output);
-}
-pub trait Content<E: Engine>: Send + Sync + Sized {
-    fn content (&self) -> impl Render<E> { () }
-    fn layout (&self, area: E::Area) -> E::Area { self.content().layout(area) }
-    fn render (&self, output: &mut E::Output) { self.content().render(output) }
-}
-impl<E: Engine, C: Content<E>> Render<E> for C {
-    fn layout (&self, area: E::Area) -> E::Area { Content::layout(self, area) }
-    fn render (&self, output: &mut E::Output) { Content::render(self, output) }
-}
-impl<'a, E: Engine> Content<E> for Box<dyn Render<E> + 'a> {
-    fn content (&self) -> impl Render<E> { self }
-}
-impl<'a, E: Engine> Content<E> for Box<dyn Render<E> + Send + Sync + 'a> {
-    fn content (&self) -> impl Render<E> { self }
-}
-impl<E: Engine> Content<E> for &(dyn Render<E> + '_) {
-    fn content (&self) -> impl Render<E> { self }
-}
-pub struct Thunk<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync>(F, PhantomData<E>);
-impl<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync> Thunk<E, T, F> {
-    pub fn new (thunk: F) -> Self { Self(thunk, Default::default()) }
-}
-impl<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync> Content<E> for Thunk<E, T, F> {
-    fn content (&self) -> impl Render<E> { (self.0)() }
-}
 impl<E: Engine, T: Content<E>> Content<E> for &T {
     fn content (&self) -> impl Render<E> {
         (*self).content()
diff --git a/engine/src/output/area.rs b/engine/src/output/area.rs
new file mode 100644
index 00000000..f17bad73
--- /dev/null
+++ b/engine/src/output/area.rs
@@ -0,0 +1,84 @@
+use crate::*;
+use std::fmt::Debug;
+
+pub trait Area<N: Coordinate>: From<[N;4]> + Debug + Copy {
+    fn x (&self) -> N;
+    fn y (&self) -> N;
+    fn w (&self) -> N;
+    fn h (&self) -> N;
+    #[inline] fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
+        if self.w() < w || self.h() < h {
+            Err(format!("min {w}x{h}").into())
+        } else {
+            Ok(self)
+        }
+    }
+    #[inline] fn xy (&self) -> [N;2] {
+        [self.x(), self.y()]
+    }
+    #[inline] fn wh (&self) -> [N;2] {
+        [self.w(), self.h()]
+    }
+    #[inline] fn xywh (&self) -> [N;4] {
+        [self.x(), self.y(), self.w(), self.h()]
+    }
+    #[inline] fn clip_h (&self, h: N) -> [N;4] {
+        [self.x(), self.y(), self.w(), self.h().min(h)]
+    }
+    #[inline] fn clip_w (&self, w: N) -> [N;4] {
+        [self.x(), self.y(), self.w().min(w), self.h()]
+    }
+    #[inline] fn clip (&self, wh: impl Size<N>) -> [N;4] {
+        [self.x(), self.y(), wh.w(), wh.h()]
+    }
+    #[inline] fn set_w (&self, w: N) -> [N;4] {
+        [self.x(), self.y(), w, self.h()]
+    }
+    #[inline] fn set_h (&self, h: N) -> [N;4] {
+        [self.x(), self.y(), self.w(), h]
+    }
+    #[inline] fn x2 (&self) -> N {
+        self.x() + self.w()
+    }
+    #[inline] fn y2 (&self) -> N {
+        self.y() + self.h()
+    }
+    #[inline] fn lrtb (&self) -> [N;4] {
+        [self.x(), self.x2(), self.y(), self.y2()]
+    }
+    #[inline] fn center (&self) -> [N;2] {
+        [self.x() + self.w()/2.into(), self.y() + self.h()/2.into()]
+    }
+    #[inline] fn center_x (&self, n: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [(x + w / 2.into()).minus(n / 2.into()), y + h / 2.into(), n, 1.into()]
+    }
+    #[inline] fn center_y (&self, m: N) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [x + w / 2.into(), (y + h / 2.into()).minus(m / 2.into()), 1.into(), m]
+    }
+    #[inline] fn center_xy (&self, [n, m]: [N;2]) -> [N;4] {
+        let [x, y, w, h] = self.xywh();
+        [(x + w / 2.into()).minus(n / 2.into()), (y + h / 2.into()).minus(m / 2.into()), n, m]
+    }
+    #[inline] fn centered (&self) -> [N;2] {
+        [self.x().minus(self.w()/2.into()), self.y().minus(self.h()/2.into())]
+    }
+    fn zero () -> [N;4] {
+        [N::zero(), N::zero(), N::zero(), N::zero()]
+    }
+}
+
+impl<N: Coordinate> Area<N> for (N, N, N, N) {
+    #[inline] fn x (&self) -> N { self.0 }
+    #[inline] fn y (&self) -> N { self.1 }
+    #[inline] fn w (&self) -> N { self.2 }
+    #[inline] fn h (&self) -> N { self.3 }
+}
+
+impl<N: Coordinate> Area<N> for [N;4] {
+    #[inline] fn x (&self) -> N { self[0] }
+    #[inline] fn y (&self) -> N { self[1] }
+    #[inline] fn w (&self) -> N { self[2] }
+    #[inline] fn h (&self) -> N { self[3] }
+}
diff --git a/engine/src/output/content.rs b/engine/src/output/content.rs
new file mode 100644
index 00000000..746dcd28
--- /dev/null
+++ b/engine/src/output/content.rs
@@ -0,0 +1,17 @@
+use crate::*;
+/// Build a [Render]able out of other [Render]ables,
+/// then apply optional custom render/layout on top.
+pub trait Content<E: Engine>: Send + Sync + Sized {
+    fn content (&self) -> impl Render<E> { () }
+    fn layout (&self, area: E::Area) -> E::Area { self.content().layout(area) }
+    fn render (&self, output: &mut E::Output) { self.content().render(output) }
+}
+impl<'a, E: Engine> Content<E> for Box<dyn Render<E> + 'a> {
+    fn content (&self) -> impl Render<E> { self }
+}
+impl<'a, E: Engine> Content<E> for Box<dyn Render<E> + Send + Sync + 'a> {
+    fn content (&self) -> impl Render<E> { self }
+}
+impl<E: Engine> Content<E> for &(dyn Render<E> + '_) {
+    fn content (&self) -> impl Render<E> { self }
+}
diff --git a/engine/src/output/coordinate.rs b/engine/src/output/coordinate.rs
new file mode 100644
index 00000000..5adf9385
--- /dev/null
+++ b/engine/src/output/coordinate.rs
@@ -0,0 +1,26 @@
+use std::fmt::{Debug, Display};
+use std::ops::{Add, Sub, Mul, Div};
+
+/// A linear coordinate.
+pub trait Coordinate: Send + Sync + Copy
+    + Add<Self, Output=Self>
+    + Sub<Self, Output=Self>
+    + Mul<Self, Output=Self>
+    + Div<Self, Output=Self>
+    + Ord + PartialEq + Eq
+    + Debug + Display + Default
+    + From<u16> + Into<u16>
+    + Into<usize>
+    + Into<f64>
+{
+    #[inline] fn minus (self, other: Self) -> Self {
+        if self >= other {
+            self - other
+        } else {
+            0.into()
+        }
+    }
+    #[inline] fn zero () -> Self {
+        0.into()
+    }
+}
diff --git a/engine/src/output/render.rs b/engine/src/output/render.rs
new file mode 100644
index 00000000..5ba5e1dc
--- /dev/null
+++ b/engine/src/output/render.rs
@@ -0,0 +1,12 @@
+use crate::*;
+
+/// Custom layout and rendering.
+pub trait Render<E: Engine>: Send + Sync {
+    fn layout (&self, area: E::Area) -> E::Area;
+    fn render (&self, output: &mut E::Output);
+}
+
+impl<E: Engine, C: Content<E>> Render<E> for C {
+    fn layout (&self, area: E::Area) -> E::Area { Content::layout(self, area) }
+    fn render (&self, output: &mut E::Output) { Content::render(self, output) }
+}
diff --git a/engine/src/output/size.rs b/engine/src/output/size.rs
new file mode 100644
index 00000000..cc5fa329
--- /dev/null
+++ b/engine/src/output/size.rs
@@ -0,0 +1,32 @@
+use crate::*;
+use std::fmt::Debug;
+
+pub trait Size<N: Coordinate>: From<[N;2]> + Debug + Copy {
+    fn x (&self) -> N;
+    fn y (&self) -> N;
+    #[inline] fn w (&self) -> N { self.x() }
+    #[inline] fn h (&self) -> N { self.y() }
+    #[inline] fn wh (&self) -> [N;2] { [self.x(), self.y()] }
+    #[inline] fn clip_w (&self, w: N) -> [N;2] { [self.w().min(w), self.h()] }
+    #[inline] fn clip_h (&self, h: N) -> [N;2] { [self.w(), self.h().min(h)] }
+    #[inline] fn expect_min (&self, w: N, h: N) -> Usually<&Self> {
+        if self.w() < w || self.h() < h {
+            Err(format!("min {w}x{h}").into())
+        } else {
+            Ok(self)
+        }
+    }
+    #[inline] fn zero () -> [N;2] {
+        [N::zero(), N::zero()]
+    }
+}
+
+impl<N: Coordinate> Size<N> for (N, N) {
+    #[inline] fn x (&self) -> N { self.0 }
+    #[inline] fn y (&self) -> N { self.1 }
+}
+
+impl<N: Coordinate> Size<N> for [N;2] {
+    #[inline] fn x (&self) -> N { self[0] }
+    #[inline] fn y (&self) -> N { self[1] }
+}
diff --git a/engine/src/output/thunk.rs b/engine/src/output/thunk.rs
new file mode 100644
index 00000000..a4bbd303
--- /dev/null
+++ b/engine/src/output/thunk.rs
@@ -0,0 +1,10 @@
+use crate::*;
+use std::marker::PhantomData;
+/// Lazily-evaluated [Render]able.
+pub struct Thunk<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync>(F, PhantomData<E>);
+impl<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync> Thunk<E, T, F> {
+    pub fn new (thunk: F) -> Self { Self(thunk, Default::default()) }
+}
+impl<E: Engine, T: Render<E>, F: Fn()->T + Send + Sync> Content<E> for Thunk<E, T, F> {
+    fn content (&self) -> impl Render<E> { (self.0)() }
+}
diff --git a/engine/src/tui.rs b/engine/src/tui.rs
index 68116829..c7579dd0 100644
--- a/engine/src/tui.rs
+++ b/engine/src/tui.rs
@@ -1,11 +1,10 @@
 mod tui_output; pub use self::tui_output::*;
 mod tui_input;  pub use self::tui_input::*;
+mod tui_run;    pub use self::tui_run::*;
 
 use crate::*;
 use std::sync::{Arc, RwLock, atomic::{AtomicBool, Ordering::*}};
 use std::io::{stdout, Stdout};
-use std::time::Duration;
-use std::thread::{spawn, JoinHandle};
 
 pub use ::better_panic;
 pub(crate) use better_panic::{Settings, Verbosity};
@@ -91,74 +90,3 @@ impl Tui {
         buffer
     }
 }
-
-pub trait TuiRun<R: Render<Tui> + Handle<Tui> + Sized + 'static> {
-    /// Run an app in the main loop.
-    fn run (&self, state: &Arc<RwLock<R>>) -> Usually<()>;
-    /// Spawn the input thread.
-    fn run_input (&self, state: &Arc<RwLock<R>>, poll: Duration) -> JoinHandle<()>;
-    /// Spawn the output thread.
-    fn run_output (&self, state: &Arc<RwLock<R>>, sleep: Duration) -> JoinHandle<()>;
-}
-
-impl<T: Render<Tui> + Handle<Tui> + Sized + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
-    fn run (&self, state: &Arc<RwLock<T>>) -> Usually<()> {
-        let _input_thread = self.run_input(state, Duration::from_millis(100));
-        self.write().unwrap().setup()?;
-        let render_thread = self.run_output(state, Duration::from_millis(10));
-        render_thread.join().expect("main thread failed");
-        self.write().unwrap().teardown()?;
-        Ok(())
-    }
-    fn run_input (&self, state: &Arc<RwLock<T>>, poll: Duration) -> JoinHandle<()> {
-        let exited = self.read().unwrap().exited.clone();
-        let state  = state.clone();
-        spawn(move || loop {
-            if exited.fetch_and(true, Relaxed) {
-                break
-            }
-            if ::crossterm::event::poll(poll).is_ok() {
-                let event = ::crossterm::event::read().unwrap();
-                match event {
-                    kpat!(Ctrl-KeyCode::Char('c')) => {
-                        exited.store(true, Relaxed);
-                    },
-                    _ => {
-                        let exited = exited.clone();
-                        if let Err(e) = state.write().unwrap().handle(&TuiIn(exited, event)) {
-                            panic!("{e}")
-                        }
-                    }
-                }
-            }
-        })
-    }
-    fn run_output (&self, state: &Arc<RwLock<T>>, sleep: Duration) -> JoinHandle<()> {
-        let exited = self.read().unwrap().exited.clone();
-        let engine = self.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 });
-        spawn(move || loop {
-            if exited.fetch_and(true, Relaxed) {
-                break
-            }
-            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();
-                }
-                let mut output = TuiOut { buffer, area: [0, 0, width, height] };
-                state.render(&mut output);
-                buffer = engine.write().unwrap().flip(output.buffer, size);
-            }
-            std::thread::sleep(sleep);
-        })
-    }
-}
-
diff --git a/engine/src/tui/tui_run.rs b/engine/src/tui/tui_run.rs
new file mode 100644
index 00000000..86c895bb
--- /dev/null
+++ b/engine/src/tui/tui_run.rs
@@ -0,0 +1,75 @@
+use crate::{*, tui::*};
+use ratatui::prelude::Size;
+use std::time::Duration;
+use std::thread::{spawn, JoinHandle};
+
+pub trait TuiRun<R: Render<Tui> + Handle<Tui> + Sized + 'static> {
+    /// Run an app in the main loop.
+    fn run (&self, state: &Arc<RwLock<R>>) -> Usually<()>;
+    /// Spawn the input thread.
+    fn run_input (&self, state: &Arc<RwLock<R>>, poll: Duration) -> JoinHandle<()>;
+    /// Spawn the output thread.
+    fn run_output (&self, state: &Arc<RwLock<R>>, sleep: Duration) -> JoinHandle<()>;
+}
+
+impl<T: Render<Tui> + Handle<Tui> + Sized + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
+    fn run (&self, state: &Arc<RwLock<T>>) -> Usually<()> {
+        let _input_thread = self.run_input(state, Duration::from_millis(100));
+        self.write().unwrap().setup()?;
+        let render_thread = self.run_output(state, Duration::from_millis(10));
+        render_thread.join().expect("main thread failed");
+        self.write().unwrap().teardown()?;
+        Ok(())
+    }
+    fn run_input (&self, state: &Arc<RwLock<T>>, poll: Duration) -> JoinHandle<()> {
+        let exited = self.read().unwrap().exited.clone();
+        let state  = state.clone();
+        spawn(move || loop {
+            if exited.fetch_and(true, Relaxed) {
+                break
+            }
+            if ::crossterm::event::poll(poll).is_ok() {
+                let event = ::crossterm::event::read().unwrap();
+                match event {
+                    kpat!(Ctrl-KeyCode::Char('c')) => {
+                        exited.store(true, Relaxed);
+                    },
+                    _ => {
+                        let exited = exited.clone();
+                        if let Err(e) = state.write().unwrap().handle(&TuiIn(exited, event)) {
+                            panic!("{e}")
+                        }
+                    }
+                }
+            }
+        })
+    }
+    fn run_output (&self, state: &Arc<RwLock<T>>, sleep: Duration) -> JoinHandle<()> {
+        let exited = self.read().unwrap().exited.clone();
+        let engine = self.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 });
+        spawn(move || loop {
+            if exited.fetch_and(true, Relaxed) {
+                break
+            }
+            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();
+                }
+                let mut output = TuiOut { buffer, area: [0, 0, width, height] };
+                state.render(&mut output);
+                buffer = engine.write().unwrap().flip(output.buffer, size);
+            }
+            std::thread::sleep(sleep);
+        })
+    }
+}
+