cleanup Engine API and generalize Inset/Outset

crates/tek_core/src/engine.rs

@@ -14,19 +14,22 @@ pub trait Engine: Send + Sync + Sized {
     /// Unit of distance.
     type Unit: Number;
     type Area: Area<Self::Unit> + From<[Self::Unit;4]> + Debug;
+    type Size: Size<Self::Unit> + From<[Self::Unit;2]> + Debug;
 
     type HandleInput;
     type Handled;
 
-    // FIXME
-    fn area (&self) -> Self::Area;
-    // FIXME
-    fn with_area (&mut self, x: Self::Unit, y: Self::Unit, w: Self::Unit, h: Self::Unit)
-        -> &mut Self;
-    // FIXME
-    fn render_in (
+    #[inline] fn area (&self) -> Self::Area;
+    #[inline] fn area_mut (&mut self) -> &mut Self::Area;
+    #[inline] fn render_in (
         &mut self, area: Self::Area, widget: &impl Widget<Engine = Self>
-    ) -> Perhaps<Self::Area>;
+    ) -> Perhaps<Self::Area> {
+        let last = self.area();
+        *self.area_mut() = area;
+        let next = widget.render(self)?;
+        *self.area_mut() = last;
+        Ok(next)
+    }
 }
 
 pub trait Widget: Send + Sync {
@@ -600,6 +603,42 @@ impl<N: Number, T: Widget> Outset<N, T> {
     }
 }
 
+impl<E: Engine, T: Widget<Engine = E>> Widget for Inset<E::Unit, T> {
+    type Engine = E;
+    fn layout (&self, to: E::Area) -> Perhaps<E::Area> {
+        match *self {
+            Self::X(x, ref inner)     => Shrink::X(x + x, inner as &dyn Widget<Engine = E>),
+            Self::Y(y, ref inner)     => Shrink::Y(y + y, inner as &dyn Widget<Engine = E>),
+            Self::XY(x, y, ref inner) => Shrink::XY(x + x, y + y, inner as &dyn Widget<Engine = E>),
+        }.layout(to)
+    }
+    fn render (&self, to: &mut E) -> Perhaps<E::Area> {
+        match *self {
+            Self::X(x, ref inner)     => Plus::X(x, inner as &dyn Widget<Engine = E>),
+            Self::Y(y, ref inner)     => Plus::Y(y, inner as &dyn Widget<Engine = E>),
+            Self::XY(x, y, ref inner) => Plus::XY(x, y, inner as &dyn Widget<Engine = E>),
+        }.render(to)
+    }
+}
+
+impl<E: Engine, T: Widget<Engine = E>> Widget for Outset<E::Unit, T> {
+    type Engine = E;
+    fn layout (&self, to: E::Area) -> Perhaps<E::Area> {
+        match *self {
+            Self::X(x, ref inner)     => Grow::X(x + x, inner as &dyn Widget<Engine = E>),
+            Self::Y(y, ref inner)     => Grow::Y(y + y, inner as &dyn Widget<Engine = E>),
+            Self::XY(x, y, ref inner) => Grow::XY(x + x, y + y, inner as &dyn Widget<Engine = E>),
+        }.layout(to)
+    }
+    fn render (&self, to: &mut E) -> Perhaps<E::Area> {
+        match *self {
+            Self::X(x, ref inner)     => Plus::X(x, inner as &dyn Widget<Engine = E>),
+            Self::Y(y, ref inner)     => Plus::Y(y, inner as &dyn Widget<Engine = E>),
+            Self::XY(x, y, ref inner) => Plus::XY(x, y, inner as &dyn Widget<Engine = E>),
+        }.render(to)
+    }
+}
+
 /// Move origin point of drawing area
 pub enum Plus<N: Number, T: Widget> {
     /// Move origin to the right