refactor engine and layout into input and output

output/src/map.rs

@@ -0,0 +1,71 @@
+use crate::*;
+
+pub fn map_south<O: Output>(
+    item_offset: O::Unit,
+    item_height: O::Unit,
+    item: impl Content<O>
+) -> impl Content<O> {
+    Push::y(item_offset, Align::n(Fixed::y(item_height, Fill::x(item))))
+}
+
+pub fn map_east<O: Output>(
+    item_offset: O::Unit,
+    item_width:  O::Unit,
+    item: impl Content<O>
+) -> impl Content<O> {
+    Push::x(item_offset, Align::w(Fixed::x(item_width, Fill::y(item))))
+}
+
+pub struct Map<'a, A, B, I, F, G>(pub PhantomData<&'a()>, pub F, pub G) where
+    I: Iterator<Item = A> + Send + Sync,
+    F: Fn() -> I + Send + Sync + 'a,
+    G: Fn(A, usize)->B + Send + Sync;
+
+impl<'a, A, B, I, F, G> Map<'a, A, B, I, F, G> where
+    I: Iterator<Item = A> + Send + Sync,
+    F: Fn() -> I + Send + Sync + 'a,
+    G: Fn(A, usize)->B + Send + Sync
+{
+    pub fn new (f: F, g: G) -> Self {
+        Self(Default::default(), f, g)
+    }
+}
+
+impl<'a, E, A, B, I, F, G> Content<E> for Map<'a, A, B, I, F, G> where
+    E: Output,
+    B: Render<E>,
+    I: Iterator<Item = A> + Send + Sync,
+    F: Fn() -> I + Send + Sync + 'a,
+    G: Fn(A, usize)->B + Send + Sync
+{
+    fn layout (&self, area: E::Area) -> E::Area {
+        let Self(_, get_iterator, callback) = self;
+        let mut index = 0;
+        let [mut min_x, mut min_y] = area.center();
+        let [mut max_x, mut max_y] = area.center();
+        for item in get_iterator() {
+            let area = callback(item, index).layout(area).xywh();
+            let [x,y,w,h] = area.xywh();
+            min_x = min_x.min(x.into());
+            min_y = min_y.min(y.into());
+            max_x = max_x.max((x + w).into());
+            max_y = max_y.max((y + h).into());
+            index += 1;
+        }
+        let w = max_x - min_x;
+        let h = max_y - min_y;
+        //[min_x.into(), min_y.into(), w.into(), h.into()].into()
+        area.center_xy([w.into(), h.into()].into()).into()
+    }
+    fn render (&self, to: &mut E) {
+        let Self(_, get_iterator, callback) = self;
+        let mut index = 0;
+        //let area = self.layout(to.area());
+        for item in get_iterator() {
+            let item = callback(item, index);
+            //to.place(area.into(), &item);
+            to.place(item.layout(to.area()), &item);
+            index += 1;
+        }
+    }
+}