Auto merge of #16628 - nox:INTERPOL, r=emilio

Parse interpolation hints (fixes #15166)

<!-- Reviewable:start -->
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16628)
<!-- Reviewable:end -->

components/layout/display_list_builder.rs

@@ -58,8 +58,8 @@ use style::properties::longhands::border_image_repeat::computed_value::RepeatKey
 use style::properties::style_structs;
 use style::servo::restyle_damage::REPAINT;
 use style::values::{Either, RGBA, computed};
-use style::values::computed::{AngleOrCorner, Gradient, GradientKind, LengthOrPercentage};
-use style::values::computed::{LengthOrPercentageOrAuto, NumberOrPercentage};
+use style::values::computed::{AngleOrCorner, Gradient, GradientItem, GradientKind};
+use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto, NumberOrPercentage};
 use style::values::specified::{HorizontalDirection, VerticalDirection};
 use style_traits::CSSPixel;
 use style_traits::cursor::Cursor;
@@ -948,9 +948,15 @@ impl FragmentDisplayListBuilding for Fragment {
         // Determine the position of each stop per CSS-IMAGES § 3.4.
         //
         // FIXME(#3908, pcwalton): Make sure later stops can't be behind earlier stops.
-        let mut stops = Vec::with_capacity(gradient.stops.len());
+        let stop_items = gradient.items.iter().filter_map(|item| {
+            match *item {
+                GradientItem::ColorStop(ref stop) => Some(stop),
+                _ => None,
+            }
+        }).collect::<Vec<_>>();
+        let mut stops = Vec::with_capacity(stop_items.len());
         let mut stop_run = None;
-        for (i, stop) in gradient.stops.iter().enumerate() {
+        for (i, stop) in stop_items.iter().enumerate() {
             let offset = match stop.position {
                 None => {
                     if stop_run.is_none() {
@@ -960,14 +966,14 @@ impl FragmentDisplayListBuilding for Fragment {
                         } else {
                             // `unwrap()` here should never fail because this is the beginning of
                             // a stop run, which is always bounded by a length or percentage.
-                            position_to_offset(gradient.stops[i - 1].position.unwrap(), length)
+                            position_to_offset(stop_items[i - 1].position.unwrap(), length)
                         };
                         let (end_index, end_offset) =
-                            match gradient.stops[i..]
+                            match stop_items[i..]
                                           .iter()
                                           .enumerate()
                                           .find(|&(_, ref stop)| stop.position.is_some()) {
-                                None => (gradient.stops.len() - 1, 1.0),
+                                None => (stop_items.len() - 1, 1.0),
                                 Some((end_index, end_stop)) => {
                                     // `unwrap()` here should never fail because this is the end of
                                     // a stop run, which is always bounded by a length or

components/style/gecko/conversions.rs

@@ -16,7 +16,8 @@ use gecko_bindings::structs::{nsStyleCoord_CalcValue, nsStyleImage};
 use gecko_bindings::structs::{nsresult, SheetType};
 use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordDataMut};
 use stylesheets::{Origin, RulesMutateError};
-use values::computed::{CalcLengthOrPercentage, Gradient, Image, LengthOrPercentage, LengthOrPercentageOrAuto};
+use values::computed::{CalcLengthOrPercentage, Gradient, GradientItem, Image};
+use values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto};
 
 impl From<CalcLengthOrPercentage> for nsStyleCoord_CalcValue {
     fn from(other: CalcLengthOrPercentage) -> nsStyleCoord_CalcValue {
@@ -160,7 +161,7 @@ impl nsStyleImage {
         use values::computed::LengthOrPercentageOrKeyword;
         use values::specified::{HorizontalDirection, SizeKeyword, VerticalDirection};
 
-        let stop_count = gradient.stops.len();
+        let stop_count = gradient.items.len();
         if stop_count >= ::std::u32::MAX as usize {
             warn!("stylo: Prevented overflow due to too many gradient stops");
             return;
@@ -280,32 +281,40 @@ impl nsStyleImage {
             },
         };
 
-        for (index, stop) in gradient.stops.iter().enumerate() {
+        for (index, item) in gradient.items.iter().enumerate() {
             // NB: stops are guaranteed to be none in the gecko side by
             // default.
-            let mut coord: nsStyleCoord = nsStyleCoord::null();
-            coord.set(stop.position);
-            let color = match stop.color {
-                CSSColor::CurrentColor => {
-                    // TODO(emilio): gecko just stores an nscolor,
-                    // and it doesn't seem to support currentColor
-                    // as value in a gradient.
-                    //
-                    // Double-check it and either remove
-                    // currentColor for servo or see how gecko
-                    // handles this.
-                    0
-                },
-                CSSColor::RGBA(ref rgba) => convert_rgba_to_nscolor(rgba),
-            };
 
-            let mut stop = unsafe {
+            let mut gecko_stop = unsafe {
                 &mut (*gecko_gradient).mStops[index]
             };
+            let mut coord = nsStyleCoord::null();
+
+            match *item {
+                GradientItem::ColorStop(ref stop) => {
+                    gecko_stop.mColor = match stop.color {
+                        CSSColor::CurrentColor => {
+                            // TODO(emilio): gecko just stores an nscolor,
+                            // and it doesn't seem to support currentColor
+                            // as value in a gradient.
+                            //
+                            // Double-check it and either remove
+                            // currentColor for servo or see how gecko
+                            // handles this.
+                            0
+                        },
+                        CSSColor::RGBA(ref rgba) => convert_rgba_to_nscolor(rgba),
+                    };
+                    gecko_stop.mIsInterpolationHint = false;
+                    coord.set(stop.position);
+                },
+                GradientItem::InterpolationHint(hint) => {
+                    gecko_stop.mIsInterpolationHint = true;
+                    coord.set(Some(hint));
+                }
+            }
 
-            stop.mColor = color;
-            stop.mIsInterpolationHint = false;
-            stop.mLocation.move_from(coord);
+            gecko_stop.mLocation.move_from(coord);
         }
 
         unsafe {

components/style/values/computed/image.rs

@@ -120,7 +120,7 @@ impl ToCss for Image {
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Gradient {
     /// The color stops.
-    pub stops: Vec<ColorStop>,
+    pub items: Vec<GradientItem>,
     /// True if this is a repeating gradient.
     pub repeating: bool,
     /// Gradient kind can be linear or radial.
@@ -149,9 +149,9 @@ impl ToCss for Gradient {
                 try!(position.to_css(dest));
             },
         }
-        for stop in &self.stops {
+        for item in &self.items {
             try!(dest.write_str(", "));
-            try!(stop.to_css(dest));
+            try!(item.to_css(dest));
         }
         try!(dest.write_str(")"));
         Ok(())
@@ -169,8 +169,8 @@ impl fmt::Debug for Gradient {
             },
         }
 
-        for stop in &self.stops {
-            let _ = write!(f, ", {:?}", stop);
+        for item in &self.items {
+            let _ = write!(f, ", {:?}", item);
         }
         Ok(())
     }
@@ -182,13 +182,13 @@ impl ToComputedValue for specified::Gradient {
     #[inline]
     fn to_computed_value(&self, context: &Context) -> Gradient {
         let specified::Gradient {
-            ref stops,
+            ref items,
             repeating,
             ref gradient_kind,
             compat_mode,
         } = *self;
         Gradient {
-            stops: stops.iter().map(|s| s.to_computed_value(context)).collect(),
+            items: items.iter().map(|s| s.to_computed_value(context)).collect(),
             repeating: repeating,
             gradient_kind: gradient_kind.to_computed_value(context),
             compat_mode: compat_mode,
@@ -198,13 +198,13 @@ impl ToComputedValue for specified::Gradient {
     #[inline]
     fn from_computed_value(computed: &Gradient) -> Self {
         let Gradient {
-            ref stops,
+            ref items,
             repeating,
             ref gradient_kind,
             compat_mode,
         } = *computed;
         specified::Gradient {
-            stops: stops.iter().map(ToComputedValue::from_computed_value).collect(),
+            items: items.iter().map(ToComputedValue::from_computed_value).collect(),
             repeating: repeating,
             gradient_kind: ToComputedValue::from_computed_value(gradient_kind),
             compat_mode: compat_mode,
@@ -251,6 +251,53 @@ impl ToComputedValue for specified::GradientKind {
     }
 }
 
+/// Specified values for color stops and interpolation hints.
+#[derive(Clone, PartialEq, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum GradientItem {
+    /// A color stop.
+    ColorStop(ColorStop),
+    /// An interpolation hint.
+    InterpolationHint(LengthOrPercentage),
+}
+
+impl ToCss for GradientItem {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            GradientItem::ColorStop(stop) => stop.to_css(dest),
+            GradientItem::InterpolationHint(hint) => hint.to_css(dest),
+        }
+    }
+}
+
+impl ToComputedValue for specified::GradientItem {
+    type ComputedValue = GradientItem;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> GradientItem {
+        match *self {
+            specified::GradientItem::ColorStop(ref stop) => {
+                GradientItem::ColorStop(stop.to_computed_value(context))
+            },
+            specified::GradientItem::InterpolationHint(ref hint) => {
+                GradientItem::InterpolationHint(hint.to_computed_value(context))
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &GradientItem) -> Self {
+        match *computed {
+            GradientItem::ColorStop(ref stop) => {
+                specified::GradientItem::ColorStop(ToComputedValue::from_computed_value(stop))
+            },
+            GradientItem::InterpolationHint(ref hint) => {
+                specified::GradientItem::InterpolationHint(ToComputedValue::from_computed_value(hint))
+            },
+        }
+    }
+}
+
 /// Computed values for one color stop in a linear gradient.
 /// https://drafts.csswg.org/css-images/#typedef-color-stop-list
 #[derive(Clone, PartialEq, Copy)]

components/style/values/computed/mod.rs

@@ -17,8 +17,8 @@ use super::specified::grid::{TrackBreadth as GenericTrackBreadth, TrackSize as G
 
 pub use app_units::Au;
 pub use cssparser::Color as CSSColor;
-pub use self::image::{AngleOrCorner, EndingShape as GradientShape, Gradient, GradientKind, Image, ImageRect};
-pub use self::image::{LengthOrKeyword, LengthOrPercentageOrKeyword};
+pub use self::image::{AngleOrCorner, EndingShape as GradientShape, Gradient, GradientItem};
+pub use self::image::{GradientKind, Image, ImageRect, LengthOrKeyword, LengthOrPercentageOrKeyword};
 pub use super::{Auto, Either, None_};
 #[cfg(feature = "gecko")]
 pub use super::specified::{AlignItems, AlignJustifyContent, AlignJustifySelf, JustifyItems};

components/style/values/specified/image.rs

@@ -92,8 +92,8 @@ impl Image {
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Gradient {
-    /// The color stops.
-    pub stops: Vec<ColorStop>,
+    /// The color stops and interpolation hints.
+    pub items: Vec<GradientItem>,
     /// True if this is a repeating gradient.
     pub repeating: bool,
     /// Gradients can be linear or radial.
@@ -132,13 +132,13 @@ impl ToCss for Gradient {
                 }
             },
         }
-        for stop in &self.stops {
+        for item in &self.items {
             if !skipcomma {
                 try!(dest.write_str(", "));
             } else {
                 skipcomma = false;
             }
-            try!(stop.to_css(dest));
+            try!(item.to_css(dest));
         }
         dest.write_str(")")
     }
@@ -148,18 +148,18 @@ impl Gradient {
     /// Parses a gradient from the given arguments.
     pub fn parse_function(context: &ParserContext, input: &mut Parser) -> Result<Gradient, ()> {
         fn parse<F>(context: &ParserContext, input: &mut Parser, parse_kind: F)
-                    -> Result<(GradientKind, Vec<ColorStop>), ()>
+                    -> Result<(GradientKind, Vec<GradientItem>), ()>
             where F: FnOnce(&ParserContext, &mut Parser) -> Result<GradientKind, ()>
         {
             input.parse_nested_block(|input| {
                 let kind = try!(parse_kind(context, input));
-                let stops = try!(input.parse_comma_separated(|i| ColorStop::parse(context, i)));
-                Ok((kind, stops))
+                let items = try!(Gradient::parse_items(context, input));
+                Ok((kind, items))
             })
         };
         let mut repeating = false;
         let mut compat_mode = CompatMode::Modern;
-        let (gradient_kind, stops) = match_ignore_ascii_case! { &try!(input.expect_function()),
+        let (gradient_kind, items) = match_ignore_ascii_case! { &try!(input.expect_function()),
             "linear-gradient" => {
                 try!(parse(context, input, GradientKind::parse_modern_linear))
             },
@@ -195,18 +195,31 @@ impl Gradient {
             _ => { return Err(()); }
         };
 
-        // https://drafts.csswg.org/css-images/#typedef-color-stop-list
-        if stops.len() < 2 {
-            return Err(())
-        }
-
         Ok(Gradient {
-            stops: stops,
+            items: items,
             repeating: repeating,
             gradient_kind: gradient_kind,
             compat_mode: compat_mode,
         })
     }
+
+    fn parse_items(context: &ParserContext, input: &mut Parser) -> Result<Vec<GradientItem>, ()> {
+        let mut seen_stop = false;
+        let items = try!(input.parse_comma_separated(|input| {
+            if seen_stop {
+                if let Ok(hint) = input.try(|i| LengthOrPercentage::parse(context, i)) {
+                    seen_stop = false;
+                    return Ok(GradientItem::InterpolationHint(hint));
+                }
+            }
+            seen_stop = true;
+            ColorStop::parse(context, input).map(GradientItem::ColorStop)
+        }));
+        if !seen_stop || items.len() < 2 {
+            return Err(());
+        }
+        Ok(items)
+    }
 }
 
 /// Specified values for CSS linear or radial gradients.
@@ -489,7 +502,27 @@ impl AngleOrCorner {
     }
 }
 
-/// Specified values for one color stop in a linear gradient.
+/// Specified values for color stops and interpolation hints.
+/// https://drafts.csswg.org/css-images-4/#color-stop-syntax
+#[derive(Clone, PartialEq, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum GradientItem {
+    /// A color stop.
+    ColorStop(ColorStop),
+    /// An interpolation hint.
+    InterpolationHint(LengthOrPercentage),
+}
+
+impl ToCss for GradientItem {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            GradientItem::ColorStop(ref stop) => stop.to_css(dest),
+            GradientItem::InterpolationHint(ref hint) => hint.to_css(dest),
+        }
+    }
+}
+
+/// Specified values for one color stop in a gradient.
 /// https://drafts.csswg.org/css-images/#typedef-color-stop-list
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]

components/style/values/specified/mod.rs

@@ -29,8 +29,8 @@ pub use self::align::{AlignItems, AlignJustifyContent, AlignJustifySelf, Justify
 pub use self::color::Color;
 pub use self::grid::{GridLine, TrackKeyword};
 pub use self::image::{AngleOrCorner, ColorStop, EndingShape as GradientEndingShape, Gradient};
-pub use self::image::{GradientKind, HorizontalDirection, Image, ImageRect, LengthOrKeyword};
-pub use self::image::{LengthOrPercentageOrKeyword, SizeKeyword, VerticalDirection};
+pub use self::image::{GradientItem, GradientKind, HorizontalDirection, Image, ImageRect};
+pub use self::image::{LengthOrKeyword, LengthOrPercentageOrKeyword, SizeKeyword, VerticalDirection};
 pub use self::length::AbsoluteLength;
 pub use self::length::{FontRelativeLength, ViewportPercentageLength, CharacterWidth, Length, CalcLengthOrPercentage};
 pub use self::length::{Percentage, LengthOrNone, LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};