refactor engine and layout into input and output

output/src/direction.rs

@@ -0,0 +1,121 @@
+use crate::*;
+pub use self::Direction::*;
+
+/// A cardinal direction.
+#[derive(Copy, Clone, PartialEq)]
+pub enum Direction { North, South, East, West, Above, Below }
+
+impl Direction {
+    pub fn split_fixed <N: Coordinate> (self, area: impl Area<N>, a: N) -> ([N;4],[N;4]) {
+        let [x, y, w, h] = area.xywh();
+        match self {
+            North => ([x, (y+h).minus(a), w, a], [x, y, w, h.minus(a)]),
+            South => ([x, y, w, a], [x, y + a, w, h.minus(a)]),
+            East  => ([x, y, a, h], [x + a, y, w.minus(a), h]),
+            West  => ([(x+w).minus(a), y, a, h], [x, y, w - a, h]),
+            Above | Below => (area.xywh(), area.xywh())
+        }
+    }
+}
+
+pub struct Bsp<X, Y>(Direction, X, Y);
+
+impl<E: Output, A: Content<E>, B: Content<E>> Content<E> for Bsp<A, B> {
+    fn layout (&self, outer: E::Area) -> E::Area {
+        let [_, _, c] = self.areas(outer);
+        c
+    }
+    fn render (&self, to: &mut E) {
+        let [area_a, area_b, _] = self.areas(to.area());
+        let (a, b) = self.contents();
+        match self.0 {
+            Below => { to.place(area_a, a); to.place(area_b, b); },
+            _     => { to.place(area_b, b); to.place(area_a, a); }
+        }
+    }
+}
+
+impl<A, B> Bsp<A, B> {
+    pub fn n (a: A, b: B) -> Self { Self(North, a, b) }
+    pub fn s (a: A, b: B) -> Self { Self(South, a, b) }
+    pub fn e (a: A, b: B) -> Self { Self(East,  a, b) }
+    pub fn w (a: A, b: B) -> Self { Self(West,  a, b) }
+    pub fn a (a: A, b: B) -> Self { Self(Above, a, b) }
+    pub fn b (a: A, b: B) -> Self { Self(Below, a, b) }
+}
+
+pub trait BspAreas<E: Output, A: Content<E>, B: Content<E>> {
+    fn direction (&self) -> Direction;
+    fn contents (&self) -> (&A, &B);
+    fn areas (&self, outer: E::Area) -> [E::Area;3] {
+        let direction = self.direction();
+        let [x, y, w, h] = outer.xywh();
+        let (a, b) = self.contents();
+        let [ax, ay, aw, ah] = a.layout(outer).xywh();
+        let [bx, by, bw, bh] = b.layout(match direction {
+            Above | Below => outer,
+            South => [x, y + ah, w, h.minus(ah)].into(),
+            North => [x, y, w, h.minus(ah)].into(),
+            East  => [x + aw, y, w.minus(aw), h].into(),
+            West  => [x, y, w.minus(aw), h].into(),
+        }).xywh();
+        match direction {
+            Above | Below => {
+                let x = ax.min(bx);
+                let w = (ax+aw).max(bx+bw).minus(x);
+                let y = ay.min(by);
+                let h = (ay+ah).max(by+bh).minus(y);
+                [[ax, ay, aw, ah].into(), [bx, by, bw, bh].into(), [x, y, w, h].into()]
+            },
+            South => {
+                let [x, y, w, h] = outer.center_xy([aw.max(bw), ah + bh]);
+                let a = [x, y, aw, ah];
+                let b = [x, y + ah, bw, bh];
+                [a.into(), b.into(), [x, y, w, h].into()]
+            },
+            North => {
+                let [x, y, w, h] = outer.center_xy([aw.max(bw), ah + bh]);
+                let a = [x, y + bh, aw, ah];
+                let b = [x, y, bw, bh];
+                [a.into(), b.into(), [x, y, w, h].into()]
+            },
+            East => {
+                let [x, y, w, h] = outer.center_xy([aw + bw, ah.max(bh)]);
+                let a = [x, y, aw, ah];
+                let b = [x + aw, y, bw, bh];
+                [a.into(), b.into(), [x, y, w, h].into()]
+            },
+            West => {
+                let [x, y, w, h] = outer.center_xy([aw + bw, ah.max(bh)]);
+                let a = [x + bw, y, aw, ah];
+                let b = [x, y, bw, bh];
+                [a.into(), b.into(), [x, y, w, h].into()]
+            },
+        }
+    }
+}
+
+impl<E: Output, A: Content<E>, B: Content<E>> BspAreas<E, A, B> for Bsp<A, B> {
+    fn direction (&self) -> Direction { self. 0 }
+    fn contents (&self) -> (&A, &B) { (&self.1, &self.2) }
+}
+
+/// Renders multiple things on top of each other,
+#[macro_export] macro_rules! lay {
+    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::b(bsp, $expr);)*; bsp }}
+}
+
+/// Stack southward.
+#[macro_export] macro_rules! col {
+    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::s(bsp, $expr);)*; bsp }};
+}
+
+/// Stack northward.
+#[macro_export] macro_rules! col_up {
+    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::n(bsp, $expr);)*; bsp }}
+}
+
+/// Stack eastward.
+#[macro_export] macro_rules! row {
+    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::e(bsp, $expr);)*; bsp }};
+}