1 files changed, 105 insertions, 0 deletions
diff --git a/servo/components/style/values/computed/position.rs b/servo/components/style/values/computed/position.rs
new file mode 100644
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+++ b/servo/components/style/values/computed/position.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/. */
+
+//! CSS handling for the computed value of
+//! [`position`][position] values.
+//!
+//! [position]: https://drafts.csswg.org/css-backgrounds-3/#position
+
+use crate::values::computed::{Integer, LengthPercentage, NonNegativeNumber, Percentage};
+use crate::values::generics::position::AspectRatio as GenericAspectRatio;
+use crate::values::generics::position::Position as GenericPosition;
+use crate::values::generics::position::PositionComponent as GenericPositionComponent;
+use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
+use crate::values::generics::position::Ratio as GenericRatio;
+use crate::values::generics::position::ZIndex as GenericZIndex;
+pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
+use crate::{One, Zero};
+use std::cmp::{Ordering, PartialOrd};
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// The computed value of a CSS `<position>`
+pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;
+
+/// The computed value of an `auto | <position>`
+pub type PositionOrAuto = GenericPositionOrAuto<Position>;
+
+/// The computed value of a CSS horizontal position.
+pub type HorizontalPosition = LengthPercentage;
+
+/// The computed value of a CSS vertical position.
+pub type VerticalPosition = LengthPercentage;
+
+impl Position {
+    /// `50% 50%`
+    #[inline]
+    pub fn center() -> Self {
+        Self::new(
+            LengthPercentage::new_percent(Percentage(0.5)),
+            LengthPercentage::new_percent(Percentage(0.5)),
+        )
+    }
+
+    /// `0% 0%`
+    #[inline]
+    pub fn zero() -> Self {
+        Self::new(LengthPercentage::zero(), LengthPercentage::zero())
+    }
+}
+
+impl ToCss for Position {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.horizontal.to_css(dest)?;
+        dest.write_str(" ")?;
+        self.vertical.to_css(dest)
+    }
+}
+
+impl GenericPositionComponent for LengthPercentage {
+    fn is_center(&self) -> bool {
+        match self.to_percentage() {
+            Some(Percentage(per)) => per == 0.5,
+            _ => false,
+        }
+    }
+}
+
+/// A computed value for the `z-index` property.
+pub type ZIndex = GenericZIndex<Integer>;
+
+/// A computed <ratio> value.
+pub type Ratio = GenericRatio<NonNegativeNumber>;
+
+impl PartialOrd for Ratio {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        f64::partial_cmp(
+            &((self.0).0 as f64 * (other.1).0 as f64),
+            &((self.1).0 as f64 * (other.0).0 as f64),
+        )
+    }
+}
+
+impl Ratio {
+    /// Returns a new Ratio.
+    pub fn new(a: f32, b: f32) -> Self {
+        GenericRatio(a.into(), b.into())
+    }
+
+    /// Returns the used value. A ratio of 0/0 behaves as the ratio 1/0.
+    /// https://drafts.csswg.org/css-values-4/#ratios
+    pub fn used_value(self) -> Self {
+        if self.0.is_zero() && self.1.is_zero() {
+            Ratio::new(One::one(), Zero::zero())
+        } else {
+            self
+        }
+    }
+}
+
+/// A computed value for the `aspect-ratio` property.
+pub type AspectRatio = GenericAspectRatio<NonNegativeNumber>;