Implement viewport percentage length units ('vw', 'vh', 'vmin', 'vmax')

components/style/media_queries.rs

@@ -34,6 +34,8 @@ impl Range<specified::Length> {
                     let initial_font_size = longhands::font_size::get_initial_value();
                     value.to_computed_value(initial_font_size, initial_font_size)
                 }
+                &specified::Length::ViewportPercentage(value) =>
+                    value.to_computed_value(viewport_size),
                 _ => unreachable!()
             }
         };

components/style/properties.mako.rs

@@ -19,6 +19,7 @@ use cssparser::{Parser, Color, RGBA, AtRuleParser, DeclarationParser,
                 DeclarationListParser, parse_important, ToCss};
 use geom::num::Zero;
 use geom::SideOffsets2D;
+use geom::size::Size2D;
 
 use values::specified::BorderStyle;
 use values::computed::{self, ToComputedValue};
@@ -3732,6 +3733,7 @@ pub fn cascade(viewport_size: Size2D<Au>,
         let inherited_font_style = inherited_style.get_font();
         computed::Context {
             is_root_element: is_root_element,
+            viewport_size: viewport_size,
             inherited_font_weight: inherited_font_style.font_weight,
             inherited_font_size: inherited_font_style.font_size,
             inherited_height: inherited_style.get_box().height,

components/style/values.rs

@@ -52,11 +52,14 @@ pub type CSSFloat = f64;
 
 pub mod specified {
     use std::ascii::AsciiExt;
+    use std::cmp;
     use std::f64::consts::PI;
     use std::fmt;
     use std::fmt::{Formatter, Debug};
+    use std::num::{NumCast, ToPrimitive};
     use url::Url;
     use cssparser::{self, Token, Parser, ToCss, CssStringWriter};
+    use geom::size::Size2D;
     use parser::ParserContext;
     use text_writer::{self, TextWriter};
     use util::geometry::Au;
@@ -154,6 +157,51 @@ pub mod specified {
         }
     }
 
+    #[derive(Clone, PartialEq, Copy)]
+    pub enum ViewportPercentageLength {
+        Vw(CSSFloat),
+        Vh(CSSFloat),
+        Vmin(CSSFloat),
+        Vmax(CSSFloat)
+    }
+
+    impl fmt::Debug for ViewportPercentageLength {
+        #[inline] fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { self.fmt_to_css(f) }
+    }
+
+    impl ToCss for ViewportPercentageLength {
+        fn to_css<W>(&self, dest: &mut W) -> text_writer::Result where W: TextWriter {
+            match self {
+                &ViewportPercentageLength::Vw(length) => write!(dest, "{}vw", length),
+                &ViewportPercentageLength::Vh(length) => write!(dest, "{}vh", length),
+                &ViewportPercentageLength::Vmin(length) => write!(dest, "{}vmin", length),
+                &ViewportPercentageLength::Vmax(length) => write!(dest, "{}vmax", length)
+            }
+        }
+    }
+
+    impl ViewportPercentageLength {
+        pub fn to_computed_value(&self, viewport_size: Size2D<Au>) -> Au {
+            macro_rules! to_unit {
+                ($viewport_dimension:expr) => {
+                    $viewport_dimension.to_f64().unwrap() / 100.0
+                }
+            }
+
+            let value = match self {
+                &ViewportPercentageLength::Vw(length) =>
+                    length * to_unit!(viewport_size.width),
+                &ViewportPercentageLength::Vh(length) =>
+                    length * to_unit!(viewport_size.height),
+                &ViewportPercentageLength::Vmin(length) =>
+                    length * to_unit!(cmp::min(viewport_size.width, viewport_size.height)),
+                &ViewportPercentageLength::Vmax(length) =>
+                    length * to_unit!(cmp::max(viewport_size.width, viewport_size.height)),
+            };
+            NumCast::from(value).unwrap()
+        }
+    }
+
     #[derive(Clone, PartialEq, Copy)]
     pub struct CharacterWidth(pub i32);
 
@@ -173,6 +221,8 @@ pub mod specified {
     pub enum Length {
         Absolute(Au),  // application units
         FontRelative(FontRelativeLength),
+        ViewportPercentage(ViewportPercentageLength),
+
         /// HTML5 "character width", as defined in HTML5 § 14.5.4.
         ///
         /// This cannot be specified by the user directly and is only generated by
@@ -189,6 +239,7 @@ pub mod specified {
             match self {
                 &Length::Absolute(length) => write!(dest, "{}px", length.to_subpx()),
                 &Length::FontRelative(length) => length.to_css(dest),
+                &Length::ViewportPercentage(length) => length.to_css(dest),
                 &Length::ServoCharacterWidth(_)
                 => panic!("internal CSS values should never be serialized"),
             }
@@ -232,6 +283,11 @@ pub mod specified {
                 "ex" => Ok(Length::FontRelative(FontRelativeLength::Ex(value))),
                 "ch" => Err(()),
                 "rem" => Ok(Length::FontRelative(FontRelativeLength::Rem(value))),
+                // viewport percentages
+                "vw" => Ok(Length::ViewportPercentage(ViewportPercentageLength::Vw(value))),
+                "vh" => Ok(Length::ViewportPercentage(ViewportPercentageLength::Vh(value))),
+                "vmin" => Ok(Length::ViewportPercentage(ViewportPercentageLength::Vmin(value))),
+                "vmax" => Ok(Length::ViewportPercentage(ViewportPercentageLength::Vmax(value)))
                 _ => Err(())
             }
         }
@@ -701,6 +757,7 @@ pub mod computed {
     use super::specified::{AngleOrCorner};
     use super::{specified, CSSFloat};
     pub use cssparser::Color as CSSColor;
+    use geom::size::Size2D;
     use properties::longhands;
     use std::fmt;
     use url::Url;
@@ -727,6 +784,7 @@ pub mod computed {
         pub border_bottom_present: bool,
         pub border_left_present: bool,
         pub is_root_element: bool,
+        pub viewport_size: Size2D<Au>
         // TODO, as needed: viewport size, etc.
     }
 
@@ -768,6 +826,8 @@ pub mod computed {
                 &specified::Length::Absolute(length) => length,
                 &specified::Length::FontRelative(length) =>
                     length.to_computed_value(context.font_size, context.root_font_size),
+                &specified::Length::ViewportPercentage(length) =>
+                    length.to_computed_value(context.viewport_size),
                 &specified::Length::ServoCharacterWidth(length) =>
                     length.to_computed_value(context.font_size)
             }