output: more big refactors

output/src/layout/layout_bsp.rs

@@ -0,0 +1,105 @@
+use crate::*;
+use Direction::*;
+
+/// A split or layer.
+pub struct Bsp<Head, Tail>(
+    pub(crate) Direction,
+    /// First element.
+    pub(crate) Head,
+    /// Second element.
+    pub(crate) Tail,
+);
+
+impl<Head, Tail> Bsp<Head, Tail> {
+    #[inline] pub const fn n (a: Head, b: Tail) -> Self { Self(North, a, b) }
+    #[inline] pub const fn s (a: Head, b: Tail) -> Self { Self(South, a, b) }
+    #[inline] pub const fn e (a: Head, b: Tail) -> Self { Self(East,  a, b) }
+    #[inline] pub const fn w (a: Head, b: Tail) -> Self { Self(West,  a, b) }
+    #[inline] pub const fn a (a: Head, b: Tail) -> Self { Self(Above, a, b) }
+    #[inline] pub const fn b (a: Head, b: Tail) -> Self { Self(Below, a, b) }
+}
+
+impl<
+    O: Out,
+    Head: Draw<O> + Layout<O>,
+    Tail: Draw<O> + Layout<O>
+> Draw<O> for Bsp<Head, Tail> {
+    fn draw (&self, to: &mut O) {
+        let [a, b, _] = bsp_areas(to.area(), self.0, &self.1, &self.2);
+        if self.0 == Below {
+            to.place_at(a, &self.1);
+            to.place_at(b, &self.2);
+        } else {
+            to.place_at(b, &self.2);
+            to.place_at(a, &self.1);
+        }
+    }
+}
+
+impl<O: Out, Head: Layout<O>, Tail: Layout<O>> Layout<O> for Bsp<Head, Tail> {
+    fn layout (&self, area: O::Area) -> O::Area {
+        bsp_areas(area, self.0, &self.1, &self.2)[2]
+    }
+}
+
+fn bsp_areas <O: Out> (
+    area: O::Area, direction: Direction, a: &impl Layout<O>, b: &impl Layout<O>,
+) -> [O::Area;3] {
+    let [x, y, w, h] = area.xywh();
+    let [aw, ah] = a.layout(area).wh();
+    let [bw, bh] = b.layout(match direction {
+        Above | Below => area,
+        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(),
+    }).wh();
+    match direction {
+        Above | Below => {
+            let [x, y, w, h] = area.center_xy([aw.max(bw), ah.max(bh)]);
+            let a = [(x + w/2.into()).minus(aw/2.into()), (y + h/2.into()).minus(ah/2.into()), aw, ah];
+            let b = [(x + w/2.into()).minus(bw/2.into()), (y + h/2.into()).minus(bh/2.into()), bw, bh];
+            [a.into(), b.into(), [x, y, w, h].into()]
+        },
+        South => {
+            let [x, y, w, h] = area.center_xy([aw.max(bw), ah + bh]);
+            let a = [(x + w/2.into()).minus(aw/2.into()), y, aw, ah];
+            let b = [(x + w/2.into()).minus(bw/2.into()), y + ah, bw, bh];
+           [a.into(), b.into(), [x, y, w, h].into()]
+        },
+        North => {
+            let [x, y, w, h] = area.center_xy([aw.max(bw), ah + bh]);
+            let a = [(x + (w/2.into())).minus(aw/2.into()), y + bh, aw, ah];
+            let b = [(x + (w/2.into())).minus(bw/2.into()), y, bw, bh];
+            [a.into(), b.into(), [x, y, w, h].into()]
+        },
+        East => {
+            let [x, y, w, h] = area.center_xy([aw + bw, ah.max(bh)]);
+            let a = [x,      (y + h/2.into()).minus(ah/2.into()), aw, ah];
+            let b = [x + aw, (y + h/2.into()).minus(bh/2.into()), bw, bh];
+            [a.into(), b.into(), [x, y, w, h].into()]
+        },
+        West => {
+            let [x, y, w, h] = area.center_xy([aw + bw, ah.max(bh)]);
+            let a = [x + bw, (y + h/2.into()).minus(ah/2.into()), aw, ah];
+            let b = [x,      (y + h/2.into()).minus(bh/2.into()), bw, bh];
+            [a.into(), b.into(), [x, y, w, h].into()]
+        },
+    }
+}
+
+/// Stack 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 }});