Implement the unitless length quirk for background-position

components/style/properties/shorthand/background.mako.rs

@@ -194,8 +194,8 @@
                     sub_properties="background-position-x background-position-y"
                     spec="https://drafts.csswg.org/css-backgrounds-4/#the-background-position">
     use properties::longhands::{background_position_x,background_position_y};
+    use values::specified::AllowQuirks;
     use values::specified::position::Position;
-    use parser::Parse;
 
     pub fn parse_value(context: &ParserContext, input: &mut Parser) -> Result<Longhands, ()> {
         let mut position_x = background_position_x::SpecifiedValue(Vec::new());
@@ -204,7 +204,7 @@
 
         try!(input.parse_comma_separated(|input| {
             loop {
-                if let Ok(value) = input.try(|input| Position::parse(context, input)) {
+                if let Ok(value) = input.try(|input| Position::parse_quirky(context, input, AllowQuirks::Yes)) {
                     position_x.0.push(value.horizontal);
                     position_y.0.push(value.vertical);
                     any = true;

components/style/values/specified/length.rs

@@ -17,7 +17,7 @@ use std::ops::Mul;
 use style_traits::ToCss;
 use style_traits::values::specified::AllowedLengthType;
 use stylesheets::CssRuleType;
-use super::{Angle, Number, SimplifiedValueNode, SimplifiedSumNode, Time, ToComputedValue};
+use super::{AllowQuirks, Angle, Number, SimplifiedValueNode, SimplifiedSumNode, Time, ToComputedValue};
 use values::{Auto, CSSFloat, Either, FONT_MEDIUM_PX, HasViewportPercentage, None_, Normal};
 use values::ExtremumLength;
 use values::computed::{ComputedValueAsSpecified, Context};
@@ -1154,7 +1154,10 @@ impl LengthOrPercentage {
         LengthOrPercentage::Length(NoCalcLength::zero())
     }
 
-    fn parse_internal(context: &ParserContext, input: &mut Parser, num_context: AllowedLengthType)
+    fn parse_internal(context: &ParserContext,
+                      input: &mut Parser,
+                      num_context: AllowedLengthType,
+                      allow_quirks: AllowQuirks)
                       -> Result<LengthOrPercentage, ()>
     {
         match try!(input.next()) {
@@ -1162,12 +1165,9 @@ impl LengthOrPercentage {
                 NoCalcLength::parse_dimension(context, value.value, unit).map(LengthOrPercentage::Length),
             Token::Percentage(ref value) if num_context.is_ok(value.unit_value) =>
                 Ok(LengthOrPercentage::Percentage(Percentage(value.unit_value))),
-            Token::Number(ref value) => {
-                if value.value != 0. && !context.length_parsing_mode.allows_unitless_lengths() {
-                    return Err(())
-                }
-                Ok(LengthOrPercentage::Length(NoCalcLength::Absolute(AbsoluteLength::Px(value.value))))
-            }
+            Token::Number(value) if value.value == 0. ||
+                                    (num_context.is_ok(value.value) && allow_quirks.allowed(context.quirks_mode)) =>
+                Ok(LengthOrPercentage::Length(NoCalcLength::from_px(value.value))),
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                 let calc = try!(input.parse_nested_block(|i| {
                     CalcLengthOrPercentage::parse_length_or_percentage(context, i)
@@ -1181,14 +1181,14 @@ impl LengthOrPercentage {
     /// Parse a non-negative length.
     #[inline]
     pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<LengthOrPercentage, ()> {
-        Self::parse_internal(context, input, AllowedLengthType::NonNegative)
+        Self::parse_internal(context, input, AllowedLengthType::NonNegative, AllowQuirks::No)
     }
 
     /// Parse a length, treating dimensionless numbers as pixels
     ///
     /// https://www.w3.org/TR/SVG2/types.html#presentation-attribute-css-value
     pub fn parse_numbers_are_pixels(context: &ParserContext, input: &mut Parser) -> Result<LengthOrPercentage, ()> {
-        if let Ok(lop) = input.try(|i| Self::parse_internal(context, i, AllowedLengthType::All)) {
+        if let Ok(lop) = input.try(|i| Self::parse(context, i)) {
             return Ok(lop)
         }
 
@@ -1204,7 +1204,7 @@ impl LengthOrPercentage {
     pub fn parse_numbers_are_pixels_non_negative(context: &ParserContext,
                                                  input: &mut Parser)
                                                  -> Result<LengthOrPercentage, ()> {
-        if let Ok(lop) = input.try(|i| Self::parse_internal(context, i, AllowedLengthType::NonNegative)) {
+        if let Ok(lop) = input.try(|i| Self::parse_non_negative(context, i)) {
             return Ok(lop)
         }
 
@@ -1230,7 +1230,18 @@ impl LengthOrPercentage {
 impl Parse for LengthOrPercentage {
     #[inline]
     fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
-        Self::parse_internal(context, input, AllowedLengthType::All)
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl LengthOrPercentage {
+    /// Parses a length or a percentage, allowing the unitless length quirk.
+    /// https://quirks.spec.whatwg.org/#the-unitless-length-quirk
+    #[inline]
+    pub fn parse_quirky(context: &ParserContext,
+                        input: &mut Parser,
+                        allow_quirks: AllowQuirks) -> Result<Self, ()> {
+        Self::parse_internal(context, input, AllowedLengthType::All, allow_quirks)
     }
 }
 

components/style/values/specified/mod.rs

@@ -7,6 +7,7 @@
 //! TODO(emilio): Enhance docs.
 
 use app_units::Au;
+use context::QuirksMode;
 use cssparser::{self, Parser, Token};
 use euclid::size::Size2D;
 use parser::{ParserContext, Parse};
@@ -1326,3 +1327,19 @@ pub type ClipRectOrAuto = Either<ClipRect, Auto>;
 
 /// <color> | auto
 pub type ColorOrAuto = Either<CSSColor, Auto>;
+
+/// Whether quirks are allowed in this context.
+#[derive(Clone, Copy, PartialEq)]
+pub enum AllowQuirks {
+    /// Quirks are allowed.
+    Yes,
+    /// Quirks are not allowed.
+    No,
+}
+
+impl AllowQuirks {
+    /// Returns `true` if quirks are allowed in this context.
+    pub fn allowed(self, quirks_mode: QuirksMode) -> bool {
+        self == AllowQuirks::Yes && quirks_mode == QuirksMode::Quirks
+    }
+}

components/style/values/specified/position.rs

@@ -19,7 +19,7 @@ use values::computed::position as computed_position;
 use values::generics::position::{Position as GenericPosition, PositionValue, PositionWithKeyword};
 use values::generics::position::HorizontalPosition as GenericHorizontalPosition;
 use values::generics::position::VerticalPosition as GenericVerticalPosition;
-use values::specified::{LengthOrPercentage, Percentage};
+use values::specified::{AllowQuirks, LengthOrPercentage, Percentage};
 
 pub use values::generics::position::Keyword;
 
@@ -132,13 +132,23 @@ impl Position {
 
 impl Parse for Position {
     fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
-        let first = input.try(|i| PositionComponent::parse(context, i))?;
-        let second = input.try(|i| PositionComponent::parse(context, i))
+        Position::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl Position {
+    /// Parses, with quirks.
+    pub fn parse_quirky(context: &ParserContext,
+                        input: &mut Parser,
+                        allow_quirks: AllowQuirks)
+                        -> Result<Self, ()> {
+        let first = input.try(|i| PositionComponent::parse_quirky(context, i, allow_quirks))?;
+        let second = input.try(|i| PositionComponent::parse_quirky(context, i, allow_quirks))
                           .unwrap_or(Either::Second(Keyword::Center));
 
-        if let Ok(third) = input.try(|i| PositionComponent::parse(context, i)) {
+        if let Ok(third) = input.try(|i| PositionComponent::parse_quirky(context, i, allow_quirks)) {
             // There's a 3rd value.
-            if let Ok(fourth) = input.try(|i| PositionComponent::parse(context, i)) {
+            if let Ok(fourth) = input.try(|i| PositionComponent::parse_quirky(context, i, allow_quirks)) {
                 // There's a 4th value.
                 Position::from_components(Some(second), Some(fourth), Some(first), Some(third))
             } else {
@@ -173,6 +183,17 @@ impl Parse for Position {
     }
 }
 
+impl PositionComponent {
+    /// Parses, with quirks.
+    fn parse_quirky(context: &ParserContext,
+                    input: &mut Parser,
+                    allow_quirks: AllowQuirks) -> Result<Self, ()> {
+        input.try(|i| LengthOrPercentage::parse_quirky(context, i, allow_quirks))
+            .map(Either::First)
+            .or_else(|()| input.try(Keyword::parse).map(Either::Second))
+    }
+}
+
 impl PositionValue<LengthOrPercentage> {
     /// Generic function for the computed value of a position.
     fn computed_value(&self, context: &Context) -> ComputedLengthOrPercentage {