style: Move float CSS property outside mako

closes #21130

components/style/values/computed/box.rs

@@ -4,13 +4,14 @@
 
 //! Computed types for box properties.
 
-use values::computed::Number;
+use values::computed::{Context, Number, ToComputedValue};
 use values::computed::length::{LengthOrPercentage, NonNegativeLength};
 use values::generics::box_::AnimationIterationCount as GenericAnimationIterationCount;
 use values::generics::box_::Perspective as GenericPerspective;
 use values::generics::box_::VerticalAlign as GenericVerticalAlign;
 
 pub use values::specified::box_::{AnimationName, Contain, Display, OverflowClipBox};
+pub use values::specified::box_::Float as SpecifiedFloat;
 pub use values::specified::box_::{OverscrollBehavior, ScrollSnapType, TouchAction, TransitionProperty, WillChange};
 
 /// A computed value for the `vertical-align` property.
@@ -29,3 +30,56 @@ impl AnimationIterationCount {
 
 /// A computed value for the `perspective` property.
 pub type Perspective = GenericPerspective<NonNegativeLength>;
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq,
+         SpecifiedValueInfo, ToCss)]
+/// A computed value for the `float` property.
+pub enum Float {
+    Left,
+    Right,
+    None
+}
+
+impl ToComputedValue for SpecifiedFloat {
+    type ComputedValue = Float;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        let ltr = context.style().writing_mode.is_bidi_ltr();
+        // https://drafts.csswg.org/css-logical-props/#float-clear
+        match *self {
+            SpecifiedFloat::InlineStart => {
+                context.rule_cache_conditions.borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Float::Left
+                } else {
+                    Float::Right
+                }
+            },
+            SpecifiedFloat::InlineEnd => {
+                context.rule_cache_conditions.borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Float::Right
+                } else {
+                    Float::Left
+                }
+            },
+            SpecifiedFloat::Left => Float::Left,
+            SpecifiedFloat::Right => Float::Right,
+            SpecifiedFloat::None => Float::None
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> SpecifiedFloat {
+        match *computed {
+            Float::Left => SpecifiedFloat::Left,
+            Float::Right => SpecifiedFloat::Right,
+            Float::None => SpecifiedFloat::None
+        }
+    }
+}