LibWeb: Add SVG <polyline> element and test case :^)

Userland/Libraries/LibWeb/SVG/AttributeNames.h

@@ -45,6 +45,7 @@ namespace Web::SVG::AttributeNames {
     E(patternContentUnits)          \
     E(patternTransform)             \
     E(patternUnits)                 \
+    E(points)                       \
     E(pointsAtX)                    \
     E(pointsAtY)                    \
     E(pointsAtZ)                    \

Userland/Libraries/LibWeb/SVG/AttributeParser.cpp

@@ -64,6 +64,32 @@ Optional<float> AttributeParser::parse_positive_length(StringView input)
     return result;
 }
 
+Vector<Gfx::FloatPoint> AttributeParser::parse_points(StringView input)
+{
+    AttributeParser parser { input };
+
+    parser.parse_whitespace();
+
+    // FIXME: "If an odd number of coordinates is provided, then the element is in error, with the same user agent behavior
+    //        as occurs with an incorrectly specified ‘path’ element. In such error cases the user agent will drop the last,
+    //        odd coordinate and otherwise render the shape."
+    //        The parser currently doesn't notice that there is a missing coordinate, so make it notice!
+    auto coordinate_pair_sequence = parser.parse_coordinate_pair_sequence();
+
+    parser.parse_whitespace();
+    if (!parser.done())
+        return {};
+
+    // FIXME: This is awkward. Can we return Gfx::FloatPoints from some of these parsing methods instead of Vector<float>?
+    Vector<Gfx::FloatPoint> points;
+    points.ensure_capacity(coordinate_pair_sequence.size());
+
+    for (auto const& pair : coordinate_pair_sequence)
+        points.empend(pair[0], pair[1]);
+
+    return points;
+}
+
 void AttributeParser::parse_drawto()
 {
     if (match('M') || match('m')) {

Userland/Libraries/LibWeb/SVG/AttributeParser.h

@@ -9,6 +9,7 @@
 
 #include <AK/String.h>
 #include <AK/Vector.h>
+#include <LibGfx/Point.h>
 
 namespace Web::SVG {
 
@@ -42,6 +43,7 @@ public:
     static Optional<float> parse_coordinate(StringView input);
     static Optional<float> parse_length(StringView input);
     static Optional<float> parse_positive_length(StringView input);
+    static Vector<Gfx::FloatPoint> parse_points(StringView input);
 
 private:
     void parse_drawto();

Userland/Libraries/LibWeb/SVG/SVGPolylineElement.cpp

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "SVGPolylineElement.h"
+#include <LibWeb/SVG/AttributeNames.h>
+#include <LibWeb/SVG/AttributeParser.h>
+
+namespace Web::SVG {
+
+SVGPolylineElement::SVGPolylineElement(DOM::Document& document, QualifiedName qualified_name)
+    : SVGGeometryElement(document, qualified_name)
+{
+}
+
+void SVGPolylineElement::parse_attribute(FlyString const& name, String const& value)
+{
+    SVGGeometryElement::parse_attribute(name, value);
+
+    if (name == SVG::AttributeNames::points) {
+        m_points = AttributeParser::parse_points(value);
+        m_path.clear();
+    }
+}
+
+Gfx::Path& SVGPolylineElement::get_path()
+{
+    if (m_path.has_value())
+        return m_path.value();
+
+    Gfx::Path path;
+
+    if (m_points.is_empty()) {
+        m_path = move(path);
+        return m_path.value();
+    }
+
+    // 1. perform an absolute moveto operation to the first coordinate pair in the list of points
+    path.move_to(m_points.first());
+
+    // 2. for each subsequent coordinate pair, perform an absolute lineto operation to that coordinate pair.
+    for (size_t point_index = 1; point_index < m_points.size(); ++point_index)
+        path.line_to(m_points[point_index]);
+
+    m_path = move(path);
+    return m_path.value();
+}
+
+}

Userland/Libraries/LibWeb/SVG/SVGPolylineElement.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/SVG/SVGGeometryElement.h>
+
+namespace Web::SVG {
+
+class SVGPolylineElement final : public SVGGeometryElement {
+public:
+    using WrapperType = Bindings::SVGPolylineElementWrapper;
+
+    SVGPolylineElement(DOM::Document&, QualifiedName);
+    virtual ~SVGPolylineElement() override = default;
+
+    virtual void parse_attribute(FlyString const& name, String const& value) override;
+
+    virtual Gfx::Path& get_path() override;
+
+private:
+    Optional<Gfx::Path> m_path;
+
+    Vector<Gfx::FloatPoint> m_points;
+};
+
+}

Userland/Libraries/LibWeb/SVG/SVGPolylineElement.idl

@@ -0,0 +1,5 @@
+[Exposed=Window]
+interface SVGPolylineElement : SVGGeometryElement {
+};
+
+// SVGPolylineElement includes SVGAnimatedPoints;

Userland/Libraries/LibWeb/SVG/TagNames.h

@@ -16,6 +16,7 @@ namespace Web::SVG::TagNames {
     __ENUMERATE_SVG_TAG(g)          \
     __ENUMERATE_SVG_TAG(line)       \
     __ENUMERATE_SVG_TAG(path)       \
+    __ENUMERATE_SVG_TAG(polyline)   \
     __ENUMERATE_SVG_TAG(rect)       \
     __ENUMERATE_SVG_TAG(svg)