refactor engine and layout into input and output

input/src/command.rs

@@ -0,0 +1,45 @@
+use crate::*;
+pub trait Command<S>: Send + Sync + Sized {
+    fn execute (self, state: &mut S) -> Perhaps<Self>;
+    fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T> {
+        Ok(self.execute(state)?.map(wrap))
+    }
+}
+#[macro_export] macro_rules! input_to_command {
+    (<$($l:lifetime),+> $Command:ty: |$state:ident:$State:ty, $input:ident:$Input:ty| $handler:expr) => {
+        impl<$($l),+> InputToCommand<$Input, $State> for $Command {
+            fn input_to_command ($state: &$State, $input: &$Input) -> Option<Self> {
+                Some($handler)
+            }
+        }
+    };
+    ($Command:ty: |$state:ident:$State:ty, $input:ident:$Input:ty| $handler:expr) => {
+        impl InputToCommand<$Input, $State> for $Command {
+            fn input_to_command ($state: &$State, $input: &$Input) -> Option<Self> {
+                Some($handler)
+            }
+        }
+    }
+}
+
+pub trait InputToCommand<I, S>: Command<S> + Sized {
+    fn input_to_command (state: &S, input: &I) -> Option<Self>;
+    fn execute_with_state (state: &mut S, input: &I) -> Perhaps<bool> {
+        Ok(if let Some(command) = Self::input_to_command(state, input) {
+            let _undo = command.execute(state)?;
+            Some(true)
+        } else {
+            None
+        })
+    }
+}
+
+#[macro_export] macro_rules! command {
+    ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
+        impl$(<$($l),+>)? Command<$State> for $Command {
+            fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
+                Ok($handler)
+            }
+        }
+    };
+}

input/src/engine.rs

@@ -0,0 +1,15 @@
+use crate::*;
+
+/// Event source
+pub trait Input: Send + Sync + Sized {
+    /// Type of input event
+    type Event;
+    /// Result of handling input
+    type Handled;
+    /// Currently handled event
+    fn event (&self) -> &Self::Event;
+    /// Whether component should exit
+    fn is_done (&self) -> bool;
+    /// Mark component as done
+    fn done (&self);
+}

input/src/event_map.rs

@@ -0,0 +1,43 @@
+use crate::*;
+
+pub struct EventMap<'a, S, I: PartialEq, C> {
+    pub bindings: &'a [(I, &'a dyn Fn(&S) -> Option<C>)],
+    pub fallback: Option<&'a dyn Fn(&S, &I) -> Option<C>>
+}
+impl<'a, S, I: PartialEq, C> EventMap<'a, S, I, C> {
+    pub fn handle (&self, state: &S, input: &I) -> Option<C> {
+        for (binding, handler) in self.bindings.iter() {
+            if input == binding {
+                return handler(state)
+            }
+        }
+        if let Some(fallback) = self.fallback {
+            fallback(state, input)
+        } else {
+            None
+        }
+    }
+}
+
+#[macro_export] macro_rules! keymap {
+    (
+        $(<$lt:lifetime>)? $KEYS:ident = |$state:ident: $State:ty, $input:ident: $Input:ty| $Command:ty
+        { $($key:expr => $handler:expr),* $(,)? } $(,)?
+    ) => {
+        pub const $KEYS: EventMap<'static, $State, $Input, $Command> = EventMap {
+            fallback: None,
+            bindings: &[ $(($key, &|$state|Some($handler)),)* ]
+        };
+        input_to_command!($(<$lt>)? $Command: |$state: $State, input: $Input|$KEYS.handle($state, input)?);
+    };
+    (
+        $(<$lt:lifetime>)? $KEYS:ident = |$state:ident: $State:ty, $input:ident: $Input:ty| $Command:ty
+        { $($key:expr => $handler:expr),* $(,)? }, $default:expr
+    ) => {
+        pub const $KEYS: EventMap<'static, $State, $Input, $Command> = EventMap {
+            fallback: Some(&|$state, $input|Some($default)),
+            bindings: &[ $(($key, &|$state|Some($handler)),)* ]
+        };
+        input_to_command!($(<$lt>)? $Command: |$state: $State, input: $Input|$KEYS.handle($state, input)?);
+    };
+}

input/src/handle.rs

@@ -0,0 +1,61 @@
+use crate::*;
+use std::sync::{Mutex, Arc, RwLock};
+
+/// Implement the [Handle] trait.
+#[macro_export] macro_rules! handle {
+    (|$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
+        impl<E: Engine> Handle<E> for $Struct {
+            fn handle (&mut $self, $input: &E) -> Perhaps<E::Handled> {
+                $handler
+            }
+        }
+    };
+    ($E:ty: |$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
+        impl Handle<$E> for $Struct {
+            fn handle (&mut $self, $input: &$E) -> Perhaps<<$E as Input>::Handled> {
+                $handler
+            }
+        }
+    }
+}
+
+/// Handle input
+pub trait Handle<E: Input>: Send + Sync {
+    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
+        Ok(None)
+    }
+}
+impl<E: Input, H: Handle<E>> Handle<E> for &mut H {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        (*self).handle(context)
+    }
+}
+impl<E: Input, H: Handle<E>> Handle<E> for Option<H> {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        if let Some(ref mut handle) = self {
+            handle.handle(context)
+        } else {
+            Ok(None)
+        }
+    }
+}
+impl<H, E: Input> Handle<E> for Mutex<H> where H: Handle<E> {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        self.get_mut().unwrap().handle(context)
+    }
+}
+impl<H, E: Input> Handle<E> for Arc<Mutex<H>> where H: Handle<E> {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        self.lock().unwrap().handle(context)
+    }
+}
+impl<H, E: Input> Handle<E> for RwLock<H> where H: Handle<E> {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        self.write().unwrap().handle(context)
+    }
+}
+impl<H, E: Input> Handle<E> for Arc<RwLock<H>> where H: Handle<E> {
+    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
+        self.write().unwrap().handle(context)
+    }
+}

input/src/lib.rs

@@ -0,0 +1,65 @@
+#![feature(associated_type_defaults)]
+
+//mod component; pub use self::component::*;
+mod engine; pub use self::engine::*;
+mod handle; pub use self::handle::*;
+mod command; pub use self::command::*;
+mod event_map; pub use self::event_map::*;
+
+pub(crate) use std::marker::PhantomData;
+pub(crate) use std::error::Error;
+
+/// Standard result type.
+pub(crate) type Usually<T> = Result<T, Box<dyn Error>>;
+
+/// Standard optional result type.
+pub(crate) type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
+
+#[cfg(test)] #[test] fn test_dimensions () {
+    assert_eq!(Area::center(&[10u16, 10, 20, 20]), [20, 20]);
+}
+
+#[cfg(test)] #[test] fn test_stub_engine () -> Usually<()> {
+    struct TestEngine(bool);
+    struct TestInput(bool);
+    struct TestOutput([u16;4]);
+    enum TestEvent { Test1 }
+    impl Engine for TestEngine {
+        type Input   = TestInput;
+        type Handled = ();
+        type Output  = TestOutput;
+        type Unit    = u16;
+        type Size    = [u16;2];
+        type Area    = [u16;4];
+        fn exited (&self) -> bool {
+            self.0
+        }
+    }
+    impl Input<TestEngine> for TestInput {
+        type Event = TestEvent;
+        fn event (&self) -> &Self::Event {
+            &TestEvent::Test1
+        }
+        fn is_done (&self) -> bool {
+            self.0
+        }
+        fn done (&self) {}
+    }
+    impl Output<TestEngine> for TestOutput {
+        fn area (&self) -> [u16;4] {
+            self.0
+        }
+        fn area_mut (&mut self) -> &mut [u16;4] {
+            &mut self.0
+        }
+        fn place (&mut self, _: [u16;4], _: &impl Render<TestEngine>) {
+            ()
+        }
+    }
+    impl Content<TestEngine> for String {
+        fn render (&self, to: &mut TestOutput) {
+            to.area_mut().set_w(self.len() as u16);
+        }
+    }
+    Ok(())
+}