Add support for MaxLength

This builds on the ExtremumLength type from the previous commit.

components/style/values/computed/length.rs

@@ -601,3 +601,58 @@ impl ToCss for MinLength {
         }
     }
 }
+
+/// A value suitable for a `max-width` or `max-height` property.
+/// See specified/values/length.rs for more details.
+#[derive(Debug, Copy, Clone, PartialEq)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[allow(missing_docs)]
+pub enum MaxLength {
+    LengthOrPercentage(LengthOrPercentage),
+    None,
+    ExtremumLength(ExtremumLength),
+}
+
+impl ToComputedValue for specified::MaxLength {
+    type ComputedValue = MaxLength;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> MaxLength {
+        match *self {
+            specified::MaxLength::LengthOrPercentage(ref lop) => {
+                MaxLength::LengthOrPercentage(lop.to_computed_value(context))
+            }
+            specified::MaxLength::None => {
+                MaxLength::None
+            }
+            specified::MaxLength::ExtremumLength(ref ext) => {
+                MaxLength::ExtremumLength(ext.clone())
+            }
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &MaxLength) -> Self {
+        match *computed {
+            MaxLength::None =>
+                specified::MaxLength::None,
+            MaxLength::LengthOrPercentage(ref lop) =>
+                specified::MaxLength::LengthOrPercentage(specified::LengthOrPercentage::from_computed_value(&lop)),
+            MaxLength::ExtremumLength(ref ext) =>
+                specified::MaxLength::ExtremumLength(ext.clone()),
+        }
+    }
+}
+
+impl ToCss for MaxLength {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            MaxLength::LengthOrPercentage(lop) =>
+                lop.to_css(dest),
+            MaxLength::None =>
+                dest.write_str("none"),
+            MaxLength::ExtremumLength(ext) =>
+                ext.to_css(dest),
+        }
+    }
+}

components/style/values/computed/mod.rs

@@ -23,7 +23,7 @@ pub use super::specified::{Angle, BorderStyle, GridLine, Time, UrlOrNone};
 pub use super::specified::url::{SpecifiedUrl, UrlExtraData};
 pub use self::length::{CalcLengthOrPercentage, Length, LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};
 pub use self::length::{LengthOrPercentageOrAutoOrContent, LengthOrPercentageOrNone, LengthOrNone};
-pub use self::length::MinLength;
+pub use self::length::{MaxLength, MinLength};
 pub use self::position::Position;
 
 pub mod basic_shape;

components/style/values/specified/length.rs

@@ -1353,3 +1353,49 @@ impl Parse for MinLength {
             })
     }
 }
+
+/// A value suitable for a `max-width` or `max-height` property.
+#[derive(Debug, Clone, PartialEq)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[allow(missing_docs)]
+pub enum MaxLength {
+    LengthOrPercentage(LengthOrPercentage),
+    None,
+    ExtremumLength(ExtremumLength),
+}
+
+impl HasViewportPercentage for MaxLength {
+    fn has_viewport_percentage(&self) -> bool {
+        match *self {
+            MaxLength::LengthOrPercentage(ref lop) => lop.has_viewport_percentage(),
+            _ => false
+        }
+    }
+}
+
+impl ToCss for MaxLength {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            MaxLength::LengthOrPercentage(ref lop) =>
+                lop.to_css(dest),
+            MaxLength::None =>
+                dest.write_str("none"),
+            MaxLength::ExtremumLength(ref ext) =>
+                ext.to_css(dest),
+        }
+    }
+}
+
+impl Parse for MaxLength {
+    fn parse(_context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
+        input.try(ExtremumLength::parse).map(MaxLength::ExtremumLength)
+            .or_else(|()| input.try(LengthOrPercentage::parse_non_negative).map(MaxLength::LengthOrPercentage))
+            .or_else(|()| {
+                match_ignore_ascii_case! { try!(input.expect_ident()),
+                    "none" =>
+                        Ok(MaxLength::None),
+                    _ => Err(())
+                }
+            })
+    }
+}

components/style/values/specified/mod.rs

@@ -30,7 +30,7 @@ pub use self::image::{SizeKeyword, VerticalDirection};
 pub use self::length::{FontRelativeLength, ViewportPercentageLength, CharacterWidth, Length, CalcLengthOrPercentage};
 pub use self::length::{Percentage, LengthOrNone, LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};
 pub use self::length::{LengthOrPercentageOrNone, LengthOrPercentageOrAutoOrContent, NoCalcLength, CalcUnit};
-pub use self::length::MinLength;
+pub use self::length::{MaxLength, MinLength};
 pub use self::position::{HorizontalPosition, Position, VerticalPosition};
 
 #[cfg(feature = "gecko")]