style: Move clear CSS property outside mako

closes #21155

components/style/values/computed/box.rs

@@ -11,7 +11,7 @@ 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_::{Clear as SpecifiedClear, Float as SpecifiedFloat};
 pub use values::specified::box_::{OverscrollBehavior, ScrollSnapType, TouchAction, TransitionProperty, WillChange};
 
 /// A computed value for the `vertical-align` property.
@@ -83,3 +83,59 @@ impl ToComputedValue for SpecifiedFloat {
         }
     }
 }
+
+#[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 `clear` property.
+pub enum Clear {
+    None,
+    Left,
+    Right,
+    Both
+}
+
+impl ToComputedValue for SpecifiedClear {
+    type ComputedValue = Clear;
+
+    #[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 {
+            SpecifiedClear::InlineStart => {
+                context.rule_cache_conditions.borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Clear::Left
+                } else {
+                    Clear::Right
+                }
+            },
+            SpecifiedClear::InlineEnd => {
+                context.rule_cache_conditions.borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Clear::Right
+                } else {
+                    Clear::Left
+                }
+            },
+            SpecifiedClear::None => Clear::None,
+            SpecifiedClear::Left => Clear::Left,
+            SpecifiedClear::Right => Clear::Right,
+            SpecifiedClear::Both => Clear::Both
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> SpecifiedClear {
+        match *computed {
+            Clear::None => SpecifiedClear::None,
+            Clear::Left => SpecifiedClear::Left,
+            Clear::Right => SpecifiedClear::Right,
+            Clear::Both => SpecifiedClear::Both,
+        }
+    }
+}