1 files changed, 67 insertions(+), 0 deletions(-)

A piet/src/conv.rs

@@ 0,0 1,67 @@
+//! Conversions of fundamental numeric and geometric types.
+
+use kurbo::Vec2;
+
+/// This is our own implementation of a "lossy From" trait, representing
+/// a conversion that can have precision loss. It is essentially adapted
+/// from <https://github.com/rust-lang/rfcs/pull/2484>.
+///
+/// If and when such a trait is standardized, we should switch to that.
+/// Alternatively, a case can be made it should move somewhere else, or
+/// we should adopt a similar trait (it has some similarity to AsPrimitive
+/// from num_traits).
+pub trait RoundFrom<T> {
+    fn round_from(x: T) -> Self;
+}
+
+/// The companion to `RoundFrom`. As with `From` and `Into`, a blanket
+/// implementation is provided; for the most part, implement `RoundFrom`.
+pub trait RoundInto<T> {
+    fn round_into(self) -> T;
+}
+
+impl<T, U> RoundInto<U> for T
+where
+    U: RoundFrom<T>,
+{
+    fn round_into(self) -> U {
+        U::round_from(self)
+    }
+}
+
+impl RoundFrom<f64> for f32 {
+    fn round_from(x: f64) -> f32 {
+        x as f32
+    }
+}
+
+impl RoundFrom<Vec2> for (f32, f32) {
+    fn round_from(p: Vec2) -> (f32, f32) {
+        (p.x as f32, p.y as f32)
+    }
+}
+
+impl RoundFrom<(f32, f32)> for Vec2 {
+    fn round_from(p: (f32, f32)) -> Vec2 {
+        Vec2::new(p.0 as f64, p.1 as f64)
+    }
+}
+
+impl RoundFrom<Vec2> for (f64, f64) {
+    fn round_from(p: Vec2) -> (f64, f64) {
+        (p.x, p.y)
+    }
+}
+
+impl RoundFrom<(f64, f64)> for Vec2 {
+    fn round_from(p: (f64, f64)) -> Vec2 {
+        Vec2::new(p.0, p.1)
+    }
+}
+
+/// Blanket implementation, no conversion needed.
+impl<T> RoundFrom<T> for T {
+    fn round_from(x: T) -> T {
+        x
+    }
+}