Implement parsing of an @viewport rule

components/style/viewport.rs

@@ -0,0 +1,302 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+use cssparser::{Parser, DeclarationListParser, AtRuleParser, DeclarationParser, ToCss, parse_important};
+use parser::{ParserContext, log_css_error};
+use stylesheets::Origin;
+use values::specified::{AllowedNumericType, Length, LengthOrPercentageOrAuto};
+
+use std::ascii::AsciiExt;
+use std::collections::hash_map::{Entry, HashMap};
+use std::fmt;
+use std::intrinsics;
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum ViewportDescriptor {
+    MinWidth(LengthOrPercentageOrAuto),
+    MaxWidth(LengthOrPercentageOrAuto),
+
+    MinHeight(LengthOrPercentageOrAuto),
+    MaxHeight(LengthOrPercentageOrAuto),
+
+    Zoom(Zoom),
+    MinZoom(Zoom),
+    MaxZoom(Zoom),
+
+    UserZoom(UserZoom),
+    Orientation(Orientation)
+}
+
+/// Zoom is a number | percentage | auto
+/// See http://dev.w3.org/csswg/css-device-adapt/#descdef-viewport-zoom
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum Zoom {
+    Number(f32),
+    Percentage(f32),
+    Auto,
+}
+
+impl ToCss for Zoom {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+        where W: fmt::Write
+    {
+        match self {
+            &Zoom::Number(number) => write!(dest, "{}", number),
+            &Zoom::Percentage(percentage) => write!(dest, "{}%", percentage * 100.),
+            &Zoom::Auto => write!(dest, "auto")
+        }
+    }
+}
+
+impl Zoom {
+    pub fn parse(input: &mut Parser) -> Result<Zoom, ()> {
+        use cssparser::Token;
+
+        match try!(input.next()) {
+            Token::Percentage(ref value) if AllowedNumericType::NonNegative.is_ok(value.unit_value) =>
+                Ok(Zoom::Percentage(value.unit_value)),
+            Token::Number(ref value) if AllowedNumericType::NonNegative.is_ok(value.value) =>
+                Ok(Zoom::Number(value.value)),
+            Token::Ident(ref value) if value.eq_ignore_ascii_case("auto") =>
+                Ok(Zoom::Auto),
+            _ => Err(())
+        }
+    }
+
+    #[inline]
+    pub fn to_f32(&self) -> Option<f32> {
+        match self {
+            &Zoom::Number(number) => Some(number as f32),
+            &Zoom::Percentage(percentage) => Some(percentage as f32),
+            &Zoom::Auto => None
+        }
+    }
+}
+
+define_css_keyword_enum!(UserZoom:
+                         "zoom" => Zoom,
+                         "fixed" => Fixed);
+
+define_css_keyword_enum!(Orientation:
+                         "auto" => Auto,
+                         "portrait" => Portrait,
+                         "landscape" => Landscape);
+
+struct ViewportRuleParser<'a, 'b: 'a> {
+    context: &'a ParserContext<'b>
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub struct ViewportDescriptorDeclaration {
+    pub origin: Origin,
+    pub descriptor: ViewportDescriptor,
+    pub important: bool
+}
+
+impl ViewportDescriptorDeclaration {
+    pub fn new(origin: Origin,
+               descriptor: ViewportDescriptor,
+               important: bool) -> ViewportDescriptorDeclaration
+    {
+        ViewportDescriptorDeclaration {
+            origin: origin,
+            descriptor: descriptor,
+            important: important
+        }
+    }
+}
+
+fn parse_shorthand(input: &mut Parser) -> Result<[LengthOrPercentageOrAuto; 2], ()> {
+    let min = try!(LengthOrPercentageOrAuto::parse_non_negative(input));
+    match input.try(|input| LengthOrPercentageOrAuto::parse_non_negative(input)) {
+        Err(()) => Ok([min.clone(), min]),
+        Ok(max) => Ok([min, max])
+    }
+}
+
+impl<'a, 'b> AtRuleParser for ViewportRuleParser<'a, 'b> {
+    type Prelude = ();
+    type AtRule = Vec<ViewportDescriptorDeclaration>;
+}
+
+impl<'a, 'b> DeclarationParser for ViewportRuleParser<'a, 'b> {
+    type Declaration = Vec<ViewportDescriptorDeclaration>;
+
+    fn parse_value(&self, name: &str, input: &mut Parser) -> Result<Vec<ViewportDescriptorDeclaration>, ()> {
+        macro_rules! declaration {
+            ($declaration:ident($parse:path)) => {
+                declaration!($declaration(value: try!($parse(input)),
+                                          important: input.try(parse_important).is_ok()))
+            };
+            ($declaration:ident(value: $value:expr, important: $important:expr)) => {
+                ViewportDescriptorDeclaration::new(
+                    self.context.stylesheet_origin,
+                    ViewportDescriptor::$declaration($value),
+                    $important)
+            }
+        }
+
+        macro_rules! ok {
+            ($declaration:ident($parse:path)) => {
+                Ok(vec![declaration!($declaration($parse))])
+            };
+            (shorthand -> [$min:ident, $max:ident]) => {{
+                let shorthand = try!(parse_shorthand(input));
+                let important = input.try(parse_important).is_ok();
+
+                Ok(vec![declaration!($min(value: shorthand[0], important: important)),
+                        declaration!($max(value: shorthand[1], important: important))])
+            }}
+        }
+
+        match name {
+            n if n.eq_ignore_ascii_case("min-width") =>
+                ok!(MinWidth(LengthOrPercentageOrAuto::parse_non_negative)),
+            n if n.eq_ignore_ascii_case("max-width") =>
+                ok!(MaxWidth(LengthOrPercentageOrAuto::parse_non_negative)),
+            n if n.eq_ignore_ascii_case("width") =>
+                ok!(shorthand -> [MinWidth, MaxWidth]),
+
+            n if n.eq_ignore_ascii_case("min-height") =>
+                ok!(MinHeight(LengthOrPercentageOrAuto::parse_non_negative)),
+            n if n.eq_ignore_ascii_case("max-height") =>
+                ok!(MaxHeight(LengthOrPercentageOrAuto::parse_non_negative)),
+            n if n.eq_ignore_ascii_case("height") =>
+                ok!(shorthand -> [MinHeight, MaxHeight]),
+
+            n if n.eq_ignore_ascii_case("zoom") =>
+                ok!(Zoom(Zoom::parse)),
+            n if n.eq_ignore_ascii_case("min-zoom") =>
+                ok!(MinZoom(Zoom::parse)),
+            n if n.eq_ignore_ascii_case("max-zoom") =>
+                ok!(MaxZoom(Zoom::parse)),
+
+            n if n.eq_ignore_ascii_case("user-zoom") =>
+                ok!(UserZoom(UserZoom::parse)),
+            n if n.eq_ignore_ascii_case("orientation") =>
+                ok!(Orientation(Orientation::parse)),
+
+            _ => Err(()),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct ViewportRule {
+    pub declarations: Vec<ViewportDescriptorDeclaration>
+}
+
+impl ViewportRule {
+    pub fn parse<'a>(input: &mut Parser, context: &'a ParserContext)
+                     -> Result<ViewportRule, ()>
+    {
+        let parser = ViewportRuleParser { context: context };
+
+        let mut errors = vec![];
+        let valid_declarations = DeclarationListParser::new(input, parser)
+            .filter_map(|result| {
+                match result {
+                    Ok(declarations) => Some(declarations),
+                    Err(range) => {
+                        errors.push(range);
+                        None
+                    }
+                }
+            })
+            .flat_map(|declarations| declarations.into_iter())
+            .collect::<Vec<_>>();
+
+        for range in errors {
+            let pos = range.start;
+            let message = format!("Unsupported @viewport descriptor declaration: '{}'",
+                                  input.slice(range));
+            log_css_error(input, pos, &*message);
+        }
+
+        Ok(ViewportRule { declarations: valid_declarations.iter().cascade() })
+    }
+}
+
+pub trait ViewportRuleCascade: Iterator + Sized {
+    fn cascade(self) -> ViewportRule;
+}
+
+impl<'a, I> ViewportRuleCascade for I
+    where I: Iterator<Item=&'a ViewportRule>
+{
+    #[inline]
+    fn cascade(self) -> ViewportRule {
+        ViewportRule {
+            declarations: self.flat_map(|r| r.declarations.iter()).cascade()
+        }
+    }
+}
+
+trait ViewportDescriptorDeclarationCascade: Iterator + Sized {
+    fn cascade(self) -> Vec<ViewportDescriptorDeclaration>;
+}
+
+/// Computes the cascade precedence as according to
+/// http://dev.w3.org/csswg/css-cascade/#cascade-origin
+fn cascade_precendence(origin: Origin, important: bool) -> u8 {
+    match (origin, important) {
+        (Origin::UserAgent, true) => 1,
+        (Origin::User, true) => 2,
+        (Origin::Author, true) => 3,
+        (Origin::Author, false) => 4,
+        (Origin::User, false) => 5,
+        (Origin::UserAgent, false) => 6,
+    }
+}
+
+impl ViewportDescriptorDeclaration {
+    fn higher_or_equal_precendence(&self, other: &ViewportDescriptorDeclaration) -> bool {
+        let self_precedence = cascade_precendence(self.origin, self.important);
+        let other_precedence = cascade_precendence(other.origin, other.important);
+
+        self_precedence <= other_precedence
+    }
+}
+
+fn cascade<'a, I>(iter: I) -> Vec<ViewportDescriptorDeclaration>
+    where I: Iterator<Item=&'a ViewportDescriptorDeclaration>
+{
+    let mut declarations: HashMap<u64, (usize, &'a ViewportDescriptorDeclaration)> = HashMap::new();
+
+    // index is used to reconstruct order of appearance after all declarations
+    // have been added to the map
+    let mut index = 0;
+    for declaration in iter {
+        let descriptor = unsafe {
+            intrinsics::discriminant_value(&declaration.descriptor)
+        };
+
+        match declarations.entry(descriptor) {
+            Entry::Occupied(mut entry) => {
+                if declaration.higher_or_equal_precendence(entry.get().1) {
+                    entry.insert((index, declaration));
+                    index += 1;
+                }
+            }
+            Entry::Vacant(entry) => {
+                entry.insert((index, declaration));
+                index += 1;
+            }
+        }
+    }
+
+    // convert to a list and sort the descriptors by order of appearance
+    let mut declarations: Vec<_> = declarations.into_iter().map(|kv| kv.1).collect();
+    declarations.sort_by(|a, b| a.0.cmp(&b.0));
+    declarations.into_iter().map(|id| *id.1).collect::<Vec<_>>()
+}
+
+impl<'a, I> ViewportDescriptorDeclarationCascade for I
+    where I: Iterator<Item=&'a ViewportDescriptorDeclaration>
+{
+    #[inline]
+    fn cascade(self) -> Vec<ViewportDescriptorDeclaration> {
+        cascade(self)
+    }
+}