LibWeb: Flesh out SVGMaskElement a bit

- Add method to resolve the masking area (based on the target element
  size)
- Parse the maskUnits and maskContentUnits attributes

Userland/Libraries/LibWeb/SVG/AttributeParser.cpp

@@ -497,15 +497,17 @@ Optional<PreserveAspectRatio> AttributeParser::parse_preserve_aspect_ratio(Strin
 }
 
 // https://svgwg.org/svg2-draft/pservers.html#LinearGradientElementGradientUnitsAttribute
-Optional<GradientUnits> AttributeParser::parse_gradient_units(StringView input)
+// https://drafts.fxtf.org/css-masking/#element-attrdef-mask-maskunits
+// https://drafts.fxtf.org/css-masking/#element-attrdef-mask-maskcontentunits
+Optional<SVGUnits> AttributeParser::parse_units(StringView input)
 {
     GenericLexer lexer { input };
     lexer.ignore_while(whitespace);
     auto gradient_units_string = lexer.consume_until(whitespace);
     if (gradient_units_string == "userSpaceOnUse"sv)
-        return GradientUnits::UserSpaceOnUse;
+        return SVGUnits::UserSpaceOnUse;
     if (gradient_units_string == "objectBoundingBox"sv)
-        return GradientUnits::ObjectBoundingBox;
+        return SVGUnits::ObjectBoundingBox;
     return {};
 }
 

Userland/Libraries/LibWeb/SVG/AttributeParser.h

@@ -88,11 +88,15 @@ struct PreserveAspectRatio {
     MeetOrSlice meet_or_slice { MeetOrSlice::Meet };
 };
 
-enum class GradientUnits {
+enum class SVGUnits {
     ObjectBoundingBox,
     UserSpaceOnUse
 };
 
+using GradientUnits = SVGUnits;
+using MaskUnits = SVGUnits;
+using MaskContentUnits = SVGUnits;
+
 enum class SpreadMethod {
     Pad,
     Repeat,
@@ -149,7 +153,7 @@ public:
     static Vector<PathInstruction> parse_path_data(StringView input);
     static Optional<Vector<Transform>> parse_transform(StringView input);
     static Optional<PreserveAspectRatio> parse_preserve_aspect_ratio(StringView input);
-    static Optional<GradientUnits> parse_gradient_units(StringView input);
+    static Optional<SVGUnits> parse_units(StringView input);
     static Optional<SpreadMethod> parse_spread_method(StringView input);
 
 private:

Userland/Libraries/LibWeb/SVG/SVGGradientElement.cpp

@@ -21,7 +21,7 @@ void SVGGradientElement::attribute_changed(DeprecatedFlyString const& name, Depr
 {
     SVGElement::attribute_changed(name, value);
     if (name == AttributeNames::gradientUnits) {
-        m_gradient_units = AttributeParser::parse_gradient_units(value);
+        m_gradient_units = AttributeParser::parse_units(value);
     } else if (name == AttributeNames::spreadMethod) {
         m_spread_method = AttributeParser::parse_spread_method(value);
     } else if (name == AttributeNames::gradientTransform) {

Userland/Libraries/LibWeb/SVG/SVGMaskElement.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -7,6 +8,7 @@
 #include <LibWeb/Bindings/SVGMaskElementPrototype.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Layout/SVGGraphicsBox.h>
+#include <LibWeb/SVG/AttributeNames.h>
 #include <LibWeb/SVG/SVGMaskElement.h>
 
 namespace Web::SVG {
@@ -29,4 +31,34 @@ JS::GCPtr<Layout::Node> SVGMaskElement::create_layout_node(NonnullRefPtr<CSS::St
     return heap().allocate_without_realm<Layout::SVGGraphicsBox>(document(), *this, move(style));
 }
 
+void SVGMaskElement::attribute_changed(DeprecatedFlyString const& name, DeprecatedString const& value)
+{
+    SVGGraphicsElement::attribute_changed(name, value);
+    if (name == AttributeNames::maskUnits) {
+        m_mask_units = AttributeParser::parse_units(value);
+    } else if (name == AttributeNames::maskContentUnits) {
+        m_mask_content_units = AttributeParser::parse_units(value);
+    }
+}
+
+MaskContentUnits SVGMaskElement::mask_content_units() const
+{
+    return m_mask_content_units.value_or(MaskContentUnits::UserSpaceOnUse);
+}
+
+MaskUnits SVGMaskElement::mask_units() const
+{
+    return m_mask_units.value_or(MaskUnits::ObjectBoundingBox);
+}
+
+CSSPixelRect SVGMaskElement::resolve_masking_area(CSSPixelRect const& mask_target) const
+{
+    if (mask_units() == SVG::MaskUnits::UserSpaceOnUse) {
+        dbgln("SVG: maskUnits=userSpaceOnUse is not supported");
+        return {};
+    }
+    // TODO: Resolve this based on the x, y, width, and height of the mask.
+    return mask_target.inflated(mask_target.size().scaled(CSSPixels(2) / 10));
+}
+
 }

Userland/Libraries/LibWeb/SVG/SVGMaskElement.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <LibWeb/SVG/AttributeParser.h>
 #include <LibWeb/SVG/SVGGraphicsElement.h>
 
 namespace Web::SVG {
@@ -16,11 +17,21 @@ class SVGMaskElement final : public SVGGraphicsElement {
 public:
     virtual ~SVGMaskElement() override;
 
+    virtual void attribute_changed(DeprecatedFlyString const& name, DeprecatedString const& value) override;
+
     virtual JS::GCPtr<Layout::Node> create_layout_node(NonnullRefPtr<CSS::StyleProperties>) override;
 
+    CSSPixelRect resolve_masking_area(CSSPixelRect const& mask_target) const;
+
+    MaskContentUnits mask_content_units() const;
+    MaskUnits mask_units() const;
+
 private:
     SVGMaskElement(DOM::Document&, DOM::QualifiedName);
     virtual void initialize(JS::Realm&) override;
+
+    Optional<MaskContentUnits> m_mask_content_units = {};
+    Optional<MaskUnits> m_mask_units = {};
 };
 
 }