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

1 files changed, 73 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/SVG/SVGCircleElement.cpp b/Userland/Libraries/LibWeb/SVG/SVGCircleElement.cpp
new file mode 100644
index 0000000000..e524859579
--- /dev/null
+++ b/Userland/Libraries/LibWeb/SVG/SVGCircleElement.cpp
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "SVGCircleElement.h"
+#include <LibWeb/SVG/AttributeNames.h>
+#include <LibWeb/SVG/AttributeParser.h>
+
+namespace Web::SVG {
+
+SVGCircleElement::SVGCircleElement(DOM::Document& document, QualifiedName qualified_name)
+    : SVGGeometryElement(document, qualified_name)
+{
+}
+
+void SVGCircleElement::parse_attribute(FlyString const& name, String const& value)
+{
+    SVGGeometryElement::parse_attribute(name, value);
+
+    if (name == SVG::AttributeNames::cx) {
+        m_center_x = AttributeParser::parse_coordinate(value);
+        m_path.clear();
+    } else if (name == SVG::AttributeNames::cy) {
+        m_center_y = AttributeParser::parse_coordinate(value);
+        m_path.clear();
+    } else if (name == SVG::AttributeNames::r) {
+        m_radius = AttributeParser::parse_positive_length(value);
+        m_path.clear();
+    }
+}
+
+Gfx::Path& SVGCircleElement::get_path()
+{
+    if (m_path.has_value())
+        return m_path.value();
+
+    float cx = m_center_x.value_or(0);
+    float cy = m_center_y.value_or(0);
+    float r = m_radius.value_or(0);
+
+    Gfx::Path path;
+
+    // A zero radius disables rendering.
+    if (r == 0) {
+        m_path = move(path);
+        return m_path.value();
+    }
+
+    bool large_arc = false;
+    bool sweep = true;
+
+    // 1. A move-to command to the point cx+r,cy;
+    path.move_to({ cx + r, cy });
+
+    // 2. arc to cx,cy+r;
+    path.arc_to({ cx, cy + r }, r, large_arc, sweep);
+
+    // 3. arc to cx-r,cy;
+    path.arc_to({ cx - r, cy }, r, large_arc, sweep);
+
+    // 4. arc to cx,cy-r;
+    path.arc_to({ cx, cy - r }, r, large_arc, sweep);
+
+    // 5. arc with a segment-completing close path operation.
+    path.arc_to({ cx + r, cy }, r, large_arc, sweep);
+
+    m_path = move(path);
+    return m_path.value();
+}
+
+}