1 files changed, 101 insertions, 0 deletions
diff --git a/servo/components/style/values/computed/angle.rs b/servo/components/style/values/computed/angle.rs
new file mode 100644
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+++ b/servo/components/style/values/computed/angle.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed angles.
+
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::CSSFloat;
+use crate::Zero;
+use std::f64::consts::PI;
+use std::fmt::{self, Write};
+use std::{f32, f64};
+use style_traits::{CssWriter, ToCss};
+
+/// A computed angle in degrees.
+#[derive(
+    Add,
+    Animate,
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+)]
+#[repr(C)]
+pub struct Angle(CSSFloat);
+
+impl ToCss for Angle {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.degrees().to_css(dest)?;
+        dest.write_str("deg")
+    }
+}
+
+const RAD_PER_DEG: f64 = PI / 180.0;
+
+impl Angle {
+    /// Creates a computed `Angle` value from a radian amount.
+    pub fn from_radians(radians: CSSFloat) -> Self {
+        Angle(radians / RAD_PER_DEG as f32)
+    }
+
+    /// Creates a computed `Angle` value from a degrees amount.
+    #[inline]
+    pub fn from_degrees(degrees: CSSFloat) -> Self {
+        Angle(degrees)
+    }
+
+    /// Returns the amount of radians this angle represents.
+    #[inline]
+    pub fn radians(&self) -> CSSFloat {
+        self.radians64().min(f32::MAX as f64).max(f32::MIN as f64) as f32
+    }
+
+    /// Returns the amount of radians this angle represents as a `f64`.
+    ///
+    /// Gecko stores angles as singles, but does this computation using doubles.
+    ///
+    /// This is significant enough to mess up rounding to the nearest
+    /// quarter-turn for 225 degrees, for example.
+    #[inline]
+    pub fn radians64(&self) -> f64 {
+        self.0 as f64 * RAD_PER_DEG
+    }
+
+    /// Return the value in degrees.
+    #[inline]
+    pub fn degrees(&self) -> CSSFloat {
+        self.0
+    }
+}
+
+impl Zero for Angle {
+    #[inline]
+    fn zero() -> Self {
+        Angle(0.0)
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+}
+
+impl ComputeSquaredDistance for Angle {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        // Use the formula for calculating the distance between angles defined in SVG:
+        // https://www.w3.org/TR/SVG/animate.html#complexDistances
+        self.radians64()
+            .compute_squared_distance(&other.radians64())
+    }
+}