implement Measure component

crates/tek_core/src/space.rs

@@ -9,6 +9,7 @@ pub trait Coordinate: Send + Sync + Copy
     + Ord + PartialEq + Eq
     + Debug + Display + Default
     + From<u16> + Into<u16>
+    + Into<usize>
     + Into<f64>
 {
     fn minus (self, other: Self) -> Self {
@@ -29,6 +30,7 @@ impl<T> Coordinate for T where
         + Ord + PartialEq + Eq
         + Debug + Display + Default
         + From<u16> + Into<u16>
+        + Into<usize>
         + Into<f64>
 {}
 
@@ -87,12 +89,10 @@ pub trait Size<N: Coordinate> {
         }
     }
 }
-
 impl<N: Coordinate> Size<N> for (N, N) {
     fn x (&self) -> N { self.0 }
     fn y (&self) -> N { self.1 }
 }
-
 impl<N: Coordinate> Size<N> for [N;2] {
     fn x (&self) -> N { self[0] }
     fn y (&self) -> N { self[1] }
@@ -880,6 +880,31 @@ impl<E: Engine, A: Widget<Engine = E>, B: Widget<Engine = E>> Widget for Split<E
     }
 }
 
+/// A widget that tracks its render width and height
+pub struct Measure<E: Engine>(PhantomData<E>, AtomicUsize, AtomicUsize);
+
+impl<E: Engine> Measure<E> {
+    pub fn w (&self) -> usize { self.1.load(Ordering::Relaxed) }
+    pub fn h (&self) -> usize { self.2.load(Ordering::Relaxed) }
+    pub fn wh (&self) -> [usize;2] { [self.w(), self.h()] }
+    pub fn set_w (&self, w: impl Into<usize>) { self.1.store(w.into(), Ordering::Relaxed) }
+    pub fn set_h (&self, h: impl Into<usize>) { self.2.store(h.into(), Ordering::Relaxed) }
+    pub fn set_wh (&self, w: impl Into<usize>, h: impl Into<usize>) { self.set_w(w); self.set_h(h); }
+    pub fn new () -> Self { Self(PhantomData::default(), 0.into(), 0.into()) }
+}
+
+impl<E: Engine> Widget for Measure<E> {
+    type Engine = E;
+    fn layout (&self, _: E::Size) -> Perhaps<E::Size> {
+        Ok(Some([0u16.into(), 0u16.into()].into()))
+    }
+    fn render (&self, to: &mut E::Output) -> Usually<()> {
+        self.set_w(to.area().w());
+        self.set_h(to.area().h());
+        Ok(())
+    }
+}
+
 /// A scrollable area.
 pub struct Scroll<
     E: Engine,