move Layout trait to separate module

- output: impl Layout for Measure, FieldH, FieldV
- tui: enable #[feature(trait_alias)]
- tui: define some trait aliases

tui/src/tui.rs

@@ -1,4 +1,5 @@
 #![feature(type_changing_struct_update)]
+#![feature(trait_alias)]
 #[cfg(test)] mod tui_test;
 mod tui_engine; pub use self::tui_engine::*;
 mod tui_content; pub use self::tui_content::*;

tui/src/tui_content/tui_field.rs

@@ -1,5 +1,12 @@
 use crate::*;
 
+impl<T: TuiContent, U: TuiContent> Draw<TuiOut> for FieldH<ItemTheme, T, U> {
+    fn draw (&self, to: &mut TuiOut) { to.place(&self.content()) }
+}
+impl<T: TuiContent, U: TuiContent> Draw<TuiOut> for FieldV<ItemTheme, T, U> {
+    fn draw (&self, to: &mut TuiOut) { to.place(&self.content()) }
+}
+
 // TODO:
 pub struct Field<T, U> {
     pub direction:   Direction,

tui/src/tui_engine.rs

@@ -73,12 +73,18 @@ impl Tui {
     }
 }
 
-pub trait TuiRun<R: Draw<TuiOut> + Handle<TuiIn> + 'static> {
+pub trait TuiDraw    = Draw<TuiOut>;
+pub trait TuiLayout  = Layout<TuiOut>;
+pub trait TuiContent = Content<TuiOut>;
+pub trait TuiHandle  = Handle<TuiIn>;
+pub trait TuiWidget  = TuiDraw + TuiHandle;
+
+pub trait TuiRun<T: TuiWidget + 'static> {
     /// Run an app in the main loop.
-    fn run (&self, state: &Arc<RwLock<R>>) -> Usually<()>;
+    fn run (&self, state: &Arc<RwLock<T>>) -> Usually<()>;
 }
 
-impl<T: Draw<TuiOut> + Handle<TuiIn> + Send + Sync + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
+impl<T: TuiWidget + Send + Sync + 'static> TuiRun<T> for Arc<RwLock<Tui>> {
     fn run (&self, state: &Arc<RwLock<T>>) -> Usually<()> {
         let _input_thread = TuiIn::run_input(self, state, Duration::from_millis(100));
         self.write().unwrap().setup()?;