Add style_traits crate to improve crate separation,

closes #7353

components/style/viewport.rs

@@ -2,19 +2,20 @@
  * 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 cssparser::{Parser, DeclarationListParser, AtRuleParser, DeclarationParser, parse_important};
 use euclid::scale_factor::ScaleFactor;
 use euclid::size::{Size2D, TypedSize2D};
 use parser::{ParserContext, log_css_error};
 use properties::longhands;
+use style_traits::viewport::{UserZoom, Zoom, Orientation, ViewportConstraints};
 use stylesheets::Origin;
-use util::geometry::{Au, PagePx, ViewportPx};
+use util::geometry::{Au, ViewportPx};
 use values::computed::{Context, ToComputedValue};
-use values::specified::{AllowedNumericType, LengthOrPercentageOrAuto};
+use values::specified::LengthOrPercentageOrAuto;
+
 
 use std::ascii::AsciiExt;
 use std::collections::hash_map::{Entry, HashMap};
-use std::fmt;
 use std::intrinsics;
 
 #[derive(Copy, Clone, Debug, PartialEq)]
@@ -33,61 +34,6 @@ pub enum ViewportDescriptor {
     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>
 }
@@ -306,40 +252,14 @@ impl<'a, I> ViewportDescriptorDeclarationCascade for I
     }
 }
 
-#[derive(Debug, PartialEq, Deserialize, Serialize)]
-pub struct ViewportConstraints {
-    pub size: TypedSize2D<ViewportPx, f32>,
-
-    pub initial_zoom: ScaleFactor<PagePx, ViewportPx, f32>,
-    pub min_zoom: Option<ScaleFactor<PagePx, ViewportPx, f32>>,
-    pub max_zoom: Option<ScaleFactor<PagePx, ViewportPx, f32>>,
-
-    pub user_zoom: UserZoom,
-    pub orientation: Orientation
+pub trait MaybeNew {
+    fn maybe_new(initial_viewport: TypedSize2D<ViewportPx, f32>,
+                     rule: &ViewportRule)
+                     -> Option<ViewportConstraints>;
 }
 
-impl ToCss for ViewportConstraints {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
-        where W: fmt::Write
-    {
-        try!(write!(dest, "@viewport {{"));
-        try!(write!(dest, " width: {}px;", self.size.width.get()));
-        try!(write!(dest, " height: {}px;", self.size.height.get()));
-        try!(write!(dest, " zoom: {};", self.initial_zoom.get()));
-        if let Some(min_zoom) = self.min_zoom {
-            try!(write!(dest, " min-zoom: {};", min_zoom.get()));
-        }
-        if let Some(max_zoom) = self.max_zoom {
-            try!(write!(dest, " max-zoom: {};", max_zoom.get()));
-        }
-        try!(write!(dest, " user-zoom: ")); try!(self.user_zoom.to_css(dest));
-        try!(write!(dest, "; orientation: ")); try!(self.orientation.to_css(dest));
-        write!(dest, "; }}")
-    }
-}
-
-impl ViewportConstraints {
-    pub fn maybe_new(initial_viewport: TypedSize2D<ViewportPx, f32>,
+impl MaybeNew for ViewportConstraints {
+    fn maybe_new(initial_viewport: TypedSize2D<ViewportPx, f32>,
                      rule: &ViewportRule)
                      -> Option<ViewportConstraints>
     {