LibWeb: Implement the color-interpolation property for SVG gradients

This changes the operating color space for gradient `<linearGradient>`
and `<radialGradient>` elements.

Libraries/LibGfx/InterpolationColorSpace.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2025, Tim Ledbetter <tim.ledbetter@ladybird.org>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+namespace Gfx {
+
+enum class InterpolationColorSpace {
+    LinearRGB,
+    SRGB,
+};
+
+}

Libraries/LibWeb/CSS/ComputedProperties.cpp

@@ -232,6 +232,12 @@ Color ComputedProperties::color_or_fallback(PropertyID id, ColorResolutionContex
     return value.to_color(color_resolution_context).value();
 }
 
+ColorInterpolation ComputedProperties::color_interpolation() const
+{
+    auto const& value = property(PropertyID::ColorInterpolation);
+    return keyword_to_color_interpolation(value.to_keyword()).value_or(CSS::ColorInterpolation::Auto);
+}
+
 // https://drafts.csswg.org/css-color-adjust-1/#determine-the-used-color-scheme
 PreferredColorScheme ComputedProperties::color_scheme(PreferredColorScheme preferred_scheme, Optional<Vector<String> const&> document_supported_schemes) const
 {

Libraries/LibWeb/CSS/ComputedProperties.h

@@ -78,6 +78,7 @@ public:
     Optional<LengthPercentage> length_percentage(PropertyID) const;
     LengthBox length_box(PropertyID left_id, PropertyID top_id, PropertyID right_id, PropertyID bottom_id, Length const& default_value) const;
     Color color_or_fallback(PropertyID, ColorResolutionContext, Color fallback) const;
+    ColorInterpolation color_interpolation() const;
     PreferredColorScheme color_scheme(PreferredColorScheme, Optional<Vector<String> const&> document_supported_schemes) const;
     TextAnchor text_anchor() const;
     TextAlign text_align() const;

Libraries/LibWeb/CSS/ComputedValues.h

@@ -104,6 +104,7 @@ public:
     static Color caret_color() { return Color::Black; }
     static CSS::Clear clear() { return CSS::Clear::None; }
     static CSS::Clip clip() { return CSS::Clip::make_auto(); }
+    static CSS::ColorInterpolation color_interpolation() { return CSS::ColorInterpolation::Auto; }
     static CSS::PreferredColorScheme color_scheme() { return CSS::PreferredColorScheme::Auto; }
     static CSS::ContentVisibility content_visibility() { return CSS::ContentVisibility::Visible; }
     static CursorData cursor() { return { CSS::CursorPredefined::Auto }; }
@@ -428,6 +429,7 @@ public:
     Color caret_color() const { return m_inherited.caret_color; }
     CSS::Clear clear() const { return m_noninherited.clear; }
     CSS::Clip clip() const { return m_noninherited.clip; }
+    CSS::ColorInterpolation color_interpolation() const { return m_inherited.color_interpolation; }
     CSS::PreferredColorScheme color_scheme() const { return m_inherited.color_scheme; }
     CSS::ContentVisibility content_visibility() const { return m_inherited.content_visibility; }
     Vector<CursorData> const& cursor() const { return m_inherited.cursor; }
@@ -638,6 +640,7 @@ protected:
         CSS::Length border_spacing_vertical { InitialValues::border_spacing() };
         CSS::CaptionSide caption_side { InitialValues::caption_side() };
         Color color { InitialValues::color() };
+        CSS::ColorInterpolation color_interpolation { InitialValues::color_interpolation() };
         CSS::PreferredColorScheme color_scheme { InitialValues::color_scheme() };
         Optional<Color> accent_color {};
         Color webkit_text_fill_color { InitialValues::color() };
@@ -837,6 +840,7 @@ public:
     void set_border_spacing_vertical(CSS::Length border_spacing_vertical) { m_inherited.border_spacing_vertical = border_spacing_vertical; }
     void set_caption_side(CSS::CaptionSide caption_side) { m_inherited.caption_side = caption_side; }
     void set_color(Color color) { m_inherited.color = color; }
+    void set_color_interpolation(CSS::ColorInterpolation color_interpolation) { m_inherited.color_interpolation = color_interpolation; }
     void set_color_scheme(CSS::PreferredColorScheme color_scheme) { m_inherited.color_scheme = color_scheme; }
     void set_clip(CSS::Clip const& clip) { m_noninherited.clip = clip; }
     void set_content(ContentData const& content) { m_noninherited.content = content; }

Libraries/LibWeb/CSS/Enums.json

@@ -132,6 +132,11 @@
     "inline-start",
     "inline-end"
   ],
+  "color-interpolation": [
+    "auto",
+    "linearrgb",
+    "srgb"
+  ],
   "column-span": [
     "none",
     "all"

Libraries/LibWeb/CSS/Keywords.json

@@ -301,6 +301,7 @@
   "lighter",
   "line-through",
   "linear",
+  "linearrgb",
   "lining-nums",
   "linktext",
   "list-item",

Libraries/LibWeb/CSS/Properties.json

@@ -1229,6 +1229,15 @@
       "hashless-hex-color"
     ]
   },
+  "color-interpolation": {
+    "affects-layout": false,
+    "animation-type": "discrete",
+    "inherited": true,
+    "initial": "srgb",
+    "valid-types": [
+      "color-interpolation"
+    ]
+  },
   "color-scheme": {
     "affects-layout": false,
     "animation-type": "discrete",

Libraries/LibWeb/Layout/Node.cpp

@@ -1017,6 +1017,7 @@ void NodeWithStyle::apply_style(CSS::ComputedProperties const& computed_style)
     computed_values.set_contain(computed_style.contain());
 
     computed_values.set_caret_color(computed_style.caret_color(*this));
+    computed_values.set_color_interpolation(computed_style.color_interpolation());
 
     propagate_style_to_anonymous_wrappers();
 

Libraries/LibWeb/Painting/DisplayListPlayerSkia.cpp

@@ -633,6 +633,9 @@ static SkPaint paint_style_to_skia_paint(Painting::SVGGradientPaintStyle const&
         shader = SkGradientShader::MakeTwoPointConical(start_center, start_radius, end_center, end_radius, colors.data(), positions.data(), color_stops.size(), tile_mode, 0, &matrix);
     }
     paint.setShader(shader);
+    if (auto* gradient_paint_style = as_if<SVGGradientPaintStyle>(paint_style); gradient_paint_style->color_space() == Gfx::InterpolationColorSpace::LinearRGB) {
+        paint.setColorFilter(SkColorFilters::LinearToSRGBGamma());
+    }
 
     return paint;
 }

Libraries/LibWeb/Painting/PaintStyle.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/AtomicRefCounted.h>
+#include <LibGfx/InterpolationColorSpace.h>
 #include <LibGfx/PaintStyle.h>
 
 namespace Web::Painting {
@@ -46,6 +47,9 @@ public:
     ReadonlySpan<ColorStop> color_stops() const { return m_color_stops; }
     Optional<float> repeat_length() const { return m_repeat_length; }
 
+    Gfx::InterpolationColorSpace color_space() const { return m_color_space; }
+    void set_color_space(Gfx::InterpolationColorSpace color_space) { m_color_space = color_space; }
+
     virtual ~SVGGradientPaintStyle() { }
 
 protected:
@@ -54,6 +58,7 @@ protected:
 
     Optional<Gfx::AffineTransform> m_gradient_transform {};
     SpreadMethod m_spread_method { SpreadMethod::Pad };
+    Gfx::InterpolationColorSpace m_color_space { Gfx::InterpolationColorSpace::SRGB };
 };
 
 class SVGLinearGradientPaintStyle final : public SVGGradientPaintStyle {

Libraries/LibWeb/SVG/SVGElement.cpp

@@ -54,6 +54,7 @@ static ReadonlySpan<NamedPropertyID> attribute_style_properties()
         NamedPropertyID(CSS::PropertyID::ClipPath),
         NamedPropertyID(CSS::PropertyID::ClipRule),
         NamedPropertyID(CSS::PropertyID::Color),
+        NamedPropertyID(CSS::PropertyID::ColorInterpolation),
         NamedPropertyID(CSS::PropertyID::Cursor),
         NamedPropertyID(CSS::PropertyID::Cx, { SVG::TagNames::circle, SVG::TagNames::ellipse }),
         NamedPropertyID(CSS::PropertyID::Cy, { SVG::TagNames::circle, SVG::TagNames::ellipse }),

Libraries/LibWeb/SVG/SVGGradientElement.cpp

@@ -66,6 +66,19 @@ SpreadMethod SVGGradientElement::spread_method_impl(HashTable<SVGGradientElement
     return SpreadMethod::Pad;
 }
 
+Gfx::InterpolationColorSpace SVGGradientElement::color_space() const
+{
+    switch (computed_properties()->color_interpolation()) {
+    case CSS::ColorInterpolation::Linearrgb:
+        return Gfx::InterpolationColorSpace::LinearRGB;
+    case CSS::ColorInterpolation::Auto:
+    case CSS::ColorInterpolation::Srgb:
+        return Gfx::InterpolationColorSpace::SRGB;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
 Optional<Gfx::AffineTransform> SVGGradientElement::gradient_transform() const
 {
     HashTable<SVGGradientElement const*> seen_gradients;

Libraries/LibWeb/SVG/SVGGradientElement.h

@@ -52,6 +52,8 @@ public:
 
     SpreadMethod spread_method() const;
 
+    Gfx::InterpolationColorSpace color_space() const;
+
     Optional<Gfx::AffineTransform> gradient_transform() const;
 
 protected:

Libraries/LibWeb/SVG/SVGLinearGradientElement.cpp

@@ -156,6 +156,7 @@ Optional<Painting::PaintStyle> SVGLinearGradientElement::to_gfx_paint_style(SVGP
 
     m_paint_style->set_gradient_transform(gradient_paint_transform(paint_context));
     m_paint_style->set_spread_method(to_painting_spread_method(spread_method()));
+    m_paint_style->set_color_space(color_space());
     return *m_paint_style;
 }
 

Libraries/LibWeb/SVG/SVGRadialGradientElement.cpp

@@ -212,6 +212,7 @@ Optional<Painting::PaintStyle> SVGRadialGradientElement::to_gfx_paint_style(SVGP
     }
     m_paint_style->set_gradient_transform(gradient_paint_transform(paint_context));
     m_paint_style->set_spread_method(to_painting_spread_method(spread_method()));
+    m_paint_style->set_color_space(color_space());
     return *m_paint_style;
 }
 

Tests/LibWeb/Ref/expected/wpt-import/svg/pservers/reftests/reference/gradient-color-interpolation-ref.svg

@@ -0,0 +1,24 @@
+<svg width="100%" height="100%"
+  xmlns="http://www.w3.org/2000/svg"
+  xmlns:html="http://www.w3.org/1999/xhtml">
+
+  <style>
+    div {
+      border: none;
+      margin: 0;
+      padding: 0;
+    };
+  </style>
+  <defs>
+    <linearGradient id="gradientLinearRGB" gradientUnits="objectBoundingBox" color-interpolation="linearRGB">
+      <stop offset="0" stop-color="white"/>
+      <stop offset=".33" stop-color="blue"/>
+      <stop offset=".66" stop-color="red"/>
+      <stop offset="1" stop-color="yellow"/>
+    </linearGradient>
+  </defs>
+
+  <foreignObject x="20" y="20" width="200" height="200">
+    <html:div style="height:100%;width:100%;background: linear-gradient(90deg in srgb-linear, white 0%, blue 33%, red 66%, yellow 100%);"/>
+  </foreignObject>
+</svg>

Tests/LibWeb/Ref/input/wpt-import/svg/pservers/reftests/gradient-color-interpolation.svg

@@ -0,0 +1,22 @@
+<svg width="100%" height="100%"
+  xmlns="http://www.w3.org/2000/svg"
+  xmlns:html="http://www.w3.org/1999/xhtml">
+  <g id="testmeta">
+    <title>Gradient with color-interpolation: linearRGB</title>
+    <html:link rel="help"
+          href="https://www.w3.org/TR/SVG2/pservers.html#LinearGradients"/>
+    <html:link rel="match" href="../../../../../expected/wpt-import/svg/pservers/reftests/reference/gradient-color-interpolation-ref.svg" />
+    <html:meta name="fuzzy" content="maxDifference=0-20;totalPixels=0-29400" />
+  </g>
+
+  <defs>
+    <linearGradient id="gradientLinearRGB" gradientUnits="objectBoundingBox" color-interpolation="linearRGB">
+      <stop offset="0" stop-color="white"/>
+      <stop offset=".33" stop-color="blue"/>
+      <stop offset=".66" stop-color="red"/>
+      <stop offset="1" stop-color="yellow"/>
+    </linearGradient>
+  </defs>
+
+  <rect x="20" y="20" width="200" height="200" style="fill:url(#gradientLinearRGB)" />
+</svg>

Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-has-indexed-property-getter.txt

@@ -8,6 +8,7 @@ All properties associated with getComputedStyle(document.body):
     "caret-color",
     "clip-rule",
     "color",
+    "color-interpolation",
     "color-scheme",
     "cursor",
     "direction",

Tests/LibWeb/Text/expected/css/CSSStyleProperties-all-supported-properties-and-default-values.txt

@@ -340,6 +340,8 @@ All supported properties and their default values exposed from CSSStylePropertie
 'clipRule': 'nonzero'
 'clip-rule': 'nonzero'
 'color': 'rgb(0, 0, 0)'
+'colorInterpolation': 'srgb'
+'color-interpolation': 'srgb'
 'colorScheme': 'normal'
 'color-scheme': 'normal'
 'columnCount': 'auto'

Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt

@@ -6,6 +6,7 @@ caption-side: top
 caret-color: rgb(0, 0, 0)
 clip-rule: nonzero
 color: rgb(0, 0, 0)
+color-interpolation: srgb
 color-scheme: normal
 cursor: auto
 direction: ltr
@@ -89,7 +90,7 @@ background-position-x: 0%
 background-position-y: 0%
 background-repeat: repeat
 background-size: auto
-block-size: 1365px
+block-size: 1380px
 border-block-end-color: rgb(0, 0, 0)
 border-block-end-style: none
 border-block-end-width: 0px
@@ -165,7 +166,7 @@ grid-row-start: auto
 grid-template-areas: none
 grid-template-columns: none
 grid-template-rows: none
-height: 2505px
+height: 2520px
 inline-size: 784px
 inset-block-end: auto
 inset-block-start: auto

Tests/LibWeb/Text/expected/wpt-import/css/css-cascade/all-prop-revert-layer.txt

@@ -1,8 +1,8 @@
 Harness status: OK
 
-Found 254 tests
+Found 255 tests
 
-247 Pass
+248 Pass
 7 Fail
 Pass	accent-color
 Pass	border-collapse
@@ -11,6 +11,7 @@ Pass	caption-side
 Pass	caret-color
 Pass	clip-rule
 Pass	color
+Pass	color-interpolation
 Pass	color-scheme
 Pass	cursor
 Pass	direction

Tests/LibWeb/Text/expected/wpt-import/css/cssom/shorthand-values.txt

@@ -2,15 +2,15 @@ Harness status: OK
 
 Found 20 tests
 
-15 Pass
+14 Pass
-5 Fail
+6 Fail
 Pass	The serialization of border: 1px; border-top: 1px; should be canonical.
 Pass	The serialization of border: 1px solid red; should be canonical.
 Pass	The serialization of border: 1px red; should be canonical.
 Pass	The serialization of border: red; should be canonical.
 Fail	The serialization of border-top: 1px; border-right: 1px; border-bottom: 1px; border-left: 1px; border-image: none; should be canonical.
 Fail	The serialization of border-top: 1px; border-right: 1px; border-bottom: 1px; border-left: 1px; should be canonical.
-Pass	The serialization of border-top: 1px; border-right: 2px; border-bottom: 3px; border-left: 4px; should be canonical.
+Fail	The serialization of border-top: 1px; border-right: 2px; border-bottom: 3px; border-left: 4px; should be canonical.
 Fail	The serialization of border: 1px; border-top: 2px; should be canonical.
 Fail	The serialization of border: 1px; border-top: 1px !important; should be canonical.
 Fail	The serialization of border: 1px; border-top-color: red; should be canonical.

Tests/LibWeb/Text/expected/wpt-import/svg/painting/parsing/color-interpolation-invalid.txt

@@ -0,0 +1,7 @@
+Harness status: OK
+
+Found 2 tests
+
+2 Pass
+Pass	e.style['color-interpolation'] = "none" should not set the property value
+Pass	e.style['color-interpolation'] = "auto srgb" should not set the property value

Tests/LibWeb/Text/expected/wpt-import/svg/painting/parsing/color-interpolation-valid.txt

@@ -0,0 +1,8 @@
+Harness status: OK
+
+Found 3 tests
+
+3 Pass
+Pass	e.style['color-interpolation'] = "auto" should set the property value
+Pass	e.style['color-interpolation'] = "srgb" should set the property value
+Pass	e.style['color-interpolation'] = "linearrgb" should set the property value

Tests/LibWeb/Text/expected/wpt-import/svg/styling/presentation-attributes-irrelevant.txt

@@ -1,12 +1,13 @@
 Harness status: OK
 
-Found 45 tests
+Found 46 tests
 
-42 Pass
+43 Pass
 3 Fail
 Pass	clip-path presentation attribute supported on an irrelevant element
 Pass	clip-rule presentation attribute supported on an irrelevant element
 Pass	color presentation attribute supported on an irrelevant element
+Pass	color-interpolation presentation attribute supported on an irrelevant element
 Pass	cursor presentation attribute supported on an irrelevant element
 Pass	direction presentation attribute supported on an irrelevant element
 Pass	display presentation attribute supported on an irrelevant element

Tests/LibWeb/Text/expected/wpt-import/svg/styling/presentation-attributes-relevant.txt

@@ -1,12 +1,13 @@
 Harness status: OK
 
-Found 55 tests
+Found 56 tests
 
-51 Pass
+52 Pass
 4 Fail
 Pass	clip-path presentation attribute supported on a relevant element
 Pass	clip-rule presentation attribute supported on a relevant element
 Pass	color presentation attribute supported on a relevant element
+Pass	color-interpolation presentation attribute supported on a relevant element
 Pass	cursor presentation attribute supported on a relevant element
 Pass	cx presentation attribute supported on a relevant element
 Pass	cy presentation attribute supported on a relevant element

Tests/LibWeb/Text/expected/wpt-import/svg/styling/presentation-attributes-unknown.txt

@@ -1,12 +1,13 @@
 Harness status: OK
 
-Found 45 tests
+Found 46 tests
 
-42 Pass
+43 Pass
 3 Fail
 Pass	clip-path presentation attribute supported on an unknown SVG element
 Pass	clip-rule presentation attribute supported on an unknown SVG element
 Pass	color presentation attribute supported on an unknown SVG element
+Pass	color-interpolation presentation attribute supported on an unknown SVG element
 Pass	cursor presentation attribute supported on an unknown SVG element
 Pass	direction presentation attribute supported on an unknown SVG element
 Pass	display presentation attribute supported on an unknown SVG element

Tests/LibWeb/Text/input/wpt-import/svg/painting/parsing/color-interpolation-invalid.svg

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     xmlns:h="http://www.w3.org/1999/xhtml"
+     width="800px" height="800px">
+  <title>SVG Painting: parsing color-interpolation with invalid values</title>
+  <metadata>
+    <h:link rel="help" href="https://svgwg.org/svg2-draft/painting.html#ColorInterpolationProperty"/>
+    <h:meta name="assert" content="color-interpolation supports only the grammar 'auto | sRGB | linearRGB'."/>
+  </metadata>
+  <g id="target"></g>
+  <h:script src="../../../resources/testharness.js"/>
+  <h:script src="../../../resources/testharnessreport.js"/>
+  <h:script src="../../../css/support/parsing-testcommon.js"/>
+  <script><![CDATA[
+
+test_invalid_value("color-interpolation", "none");
+test_invalid_value("color-interpolation", "auto srgb");
+
+  ]]></script>
+</svg>

Tests/LibWeb/Text/input/wpt-import/svg/painting/parsing/color-interpolation-valid.svg

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     xmlns:h="http://www.w3.org/1999/xhtml"
+     width="800px" height="800px">
+  <title>SVG Painting: parsing color-interpolation with valid values</title>
+  <metadata>
+    <h:link rel="help" href="https://svgwg.org/svg2-draft/painting.html#ColorInterpolationProperty"/>
+    <h:meta name="assert" content="color-interpolation supports the full grammar 'auto | sRGB | linearRGB'."/>
+  </metadata>
+  <g id="target"></g>
+  <h:script src="../../../resources/testharness.js"/>
+  <h:script src="../../../resources/testharnessreport.js"/>
+  <h:script src="../../../css/support/parsing-testcommon.js"/>
+  <script><![CDATA[
+
+test_valid_value("color-interpolation", "auto");
+test_valid_value("color-interpolation", "srgb");
+test_valid_value("color-interpolation", "linearrgb");
+
+  ]]></script>
+</svg>