2 files changed, 53 insertions, 3 deletions

diff --git a/src/platform/graphics/Geometry.cpp b/src/platform/graphics/Geometry.cpp
index 859a7bd6..896b324f 100644
--- a/src/platform/graphics/Geometry.cpp
+++ b/src/platform/graphics/Geometry.cpp
@@ -1,9 +1,11 @@
 #include "cru/platform/graphics/Geometry.h"
-
 #include "cru/base/StringUtil.h"
+#include "cru/platform/GraphicsBase.h"
+#include "cru/platform/Matrix.h"
 #include "cru/platform/graphics/Factory.h"
 
 #include <cmath>
+#include <numbers>
 #include <unordered_set>
 
 namespace cru::platform::graphics {
@@ -19,6 +21,40 @@ std::unique_ptr<IGeometry> IGeometry::CreateStrokeGeometry(
                                      "not supported on this platform.");
 }
 
+IGeometryBuilder::ArcInfo IGeometryBuilder::CalculateArcInfo(
+    const Point& start_point, const Point& radius, float angle,
+    bool is_large_arc, bool is_clockwise, const Point& end_point) {
+  auto matrix =
+      Matrix::Rotation(-angle) * Matrix::Scale(1 / radius.x, 1 / radius.y);
+  auto s1 = matrix.TransformPoint(start_point),
+       s2 = matrix.TransformPoint(end_point);
+  if (!is_clockwise) {
+    using std::swap;
+    swap(s1, s2);
+  }
+
+  auto mid = (s1 + s2) / 2;
+  auto d = s1.Distance(s2) / 2;
+  auto dc = std::sqrt(1 - d * d);
+  auto a = std::atan2(s1.x - s2.x, s2.y - s1.y);
+  Point center(mid.x - dc * std::cos(a), mid.y - dc * std::sin(a));
+
+  if (std::abs(center.x) < 0.000001) {
+    center.x = 0.f;
+  }
+  if (std::abs(center.y) < 0.000001) {
+    center.y = 0.f;
+  }
+
+  auto start_angle = std::atan2(s1.y - center.y, s1.x - center.x);
+  auto end_angle = std::atan2(s2.y - center.y, s2.x - center.x);
+  if (end_angle < 0) {
+    end_angle += std::numbers::pi_v<float> * 2;
+  }
+
+  return {matrix.Inverted()->TransformPoint(center), start_angle, end_angle};
+}
+
 void IGeometryBuilder::RelativeMoveTo(const Point& offset) {
   MoveTo(GetCurrentPosition() + offset);
 }
@@ -233,9 +269,9 @@ void IGeometryBuilder::ParseAndApplySvgPathData(std::string_view path_d) {
       ++position;
     }
 
-
     auto result = cru::string::ParseToNumber<float>(
-        path_d.substr(position), cru::string::ParseToNumberFlags::AllowTrailingJunk);
+        path_d.substr(position),
+        cru::string::ParseToNumberFlags::AllowTrailingJunk);
 
     if (!result.valid) throw Exception("Invalid svg path data number.");
 
diff --git a/src/platform/graphics/quartz/Geometry.cpp b/src/platform/graphics/quartz/Geometry.cpp
index 4c2f90a6..9b93ce15 100644
--- a/src/platform/graphics/quartz/Geometry.cpp
+++ b/src/platform/graphics/quartz/Geometry.cpp
@@ -67,6 +67,20 @@ void QuartzGeometryBuilder::QuadraticBezierTo(const Point &control_point,
                             control_point.y, end_point.x, end_point.y);
 }
 
+void QuartzGeometryBuilder::ArcTo(const Point &radius, float angle,
+                                  bool is_large_arc, bool is_clockwise,
+                                  const Point &end_point) {
+  auto info = CalculateArcInfo(GetCurrentPosition(), radius, angle,
+                               is_large_arc, is_clockwise, end_point);
+
+  auto matrix =
+      Matrix::Translation(info.center) * Matrix::Scale(radius.x, radius.y);
+  CGAffineTransform transform = Convert(matrix);
+
+  CGPathAddArc(cg_mutable_path_, &transform, 0, 0, 1, info.start_angle,
+               info.end_angle, true);
+}
+
 void QuartzGeometryBuilder::CloseFigure(bool close) {
   if (close) CGPathCloseSubpath(cg_mutable_path_);
 }