HALF WORK!

8 files changed, 118 insertions, 3 deletions

diff --git a/include/cru/platform/GraphicsBase.h b/include/cru/platform/GraphicsBase.h
index 0c391b11..4e88ca26 100644
--- a/include/cru/platform/GraphicsBase.h
+++ b/include/cru/platform/GraphicsBase.h
@@ -2,6 +2,7 @@
 #include <cru/base/Range.h>
 #include <cru/base/StringUtil.h>
 
+#include <cmath>
 #include <format>
 #include <limits>
 
@@ -21,6 +22,11 @@ struct Point final {
 
   constexpr Point Negate() const { return Point(-x, -y); }
 
+  constexpr float Distance(const Point& other) {
+    auto dx = x - other.x, dy = y - other.y;
+    return std::sqrt(dx * dx + dy * dy);
+  }
+
   std::string ToString() const {
     return std::format("Point(x: {}, y: {})", x, y);
   }
@@ -39,6 +45,10 @@ constexpr Point operator-(const Point& left, const Point& right) {
   return Point(left.x - right.x, left.y - right.y);
 }
 
+constexpr Point operator/(const Point& point, float scale) {
+  return Point(point.x / scale, point.y / scale);
+}
+
 struct Size final {
   constexpr Size() = default;
   constexpr Size(const float width, const float height)
diff --git a/include/cru/platform/graphics/Geometry.h b/include/cru/platform/graphics/Geometry.h
index ef661f2a..7d314f0a 100644
--- a/include/cru/platform/graphics/Geometry.h
+++ b/include/cru/platform/graphics/Geometry.h
@@ -63,6 +63,18 @@ struct CRU_PLATFORM_GRAPHICS_API IGeometry : virtual IGraphicsResource {
  * virtual so it can override them.
  */
 struct CRU_PLATFORM_GRAPHICS_API IGeometryBuilder : virtual IGraphicsResource {
+  struct ArcInfo {
+    Point center;
+    // In radian.
+    float start_angle;
+    // In radian.
+    float end_angle;
+  };
+
+  static ArcInfo CalculateArcInfo(const Point& start_point, const Point& radius,
+                          float angle, bool is_large_arc, bool is_clockwise,
+                          const Point& end_point);
+
   virtual Point GetCurrentPosition() = 0;
 
   virtual void MoveTo(const Point& point) = 0;
diff --git a/include/cru/platform/graphics/quartz/Geometry.h b/include/cru/platform/graphics/quartz/Geometry.h
index e13d268e..abdff00e 100644
--- a/include/cru/platform/graphics/quartz/Geometry.h
+++ b/include/cru/platform/graphics/quartz/Geometry.h
@@ -43,6 +43,9 @@ class QuartzGeometryBuilder : public OsxQuartzResource,
                      const Point& end_point) override;
   void QuadraticBezierTo(const Point& control_point,
                          const Point& end_point) override;
+  void ArcTo(const Point& radius, float angle, bool is_large_arc,
+             bool is_clockwise, const Point& end_point) override;
+
   void CloseFigure(bool close) override;
 
   std::unique_ptr<IGeometry> Build() override;
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_);
 }
diff --git a/test/platform/CMakeLists.txt b/test/platform/CMakeLists.txt
index 187068b8..6e8b8646 100644
--- a/test/platform/CMakeLists.txt
+++ b/test/platform/CMakeLists.txt
@@ -6,6 +6,8 @@ add_executable(CruPlatformBaseTest
 )
 target_link_libraries(CruPlatformBaseTest PRIVATE CruPlatformBase CruTestBase)
 
+add_subdirectory(graphics)
+
 if (WIN32)
 	add_subdirectory(graphics/direct2d)
 endif()
diff --git a/test/platform/graphics/CMakeLists.txt b/test/platform/graphics/CMakeLists.txt
new file mode 100644
index 00000000..22be21e6
--- /dev/null
+++ b/test/platform/graphics/CMakeLists.txt
@@ -0,0 +1,6 @@
+add_executable(CruPlatformGraphicsTest
+	GeometryTest.cpp
+)
+target_link_libraries(CruPlatformGraphicsTest PRIVATE CruPlatformGraphics CruTestBase)
+
+cru_catch_discover_tests(CruPlatformGraphicsTest)
diff --git a/test/platform/graphics/GeometryTest.cpp b/test/platform/graphics/GeometryTest.cpp
new file mode 100644
index 00000000..8a48ddde
--- /dev/null
+++ b/test/platform/graphics/GeometryTest.cpp
@@ -0,0 +1,32 @@
+#include "cru/platform/graphics/Geometry.h"
+
+#include <catch2/catch_test_macros.hpp>
+#include <numbers>
+#include "catch2/catch_approx.hpp"
+
+using Catch::Approx;
+using cru::platform::graphics::IGeometryBuilder;
+
+constexpr float margin = 0.000001;
+
+TEST_CASE("IGeometryBuilder CalculateArcInfo", "[graphics][geometry]") {
+  auto test = [](float start_x, float start_y, float radius_x, float radius_y,
+                 float angle, bool is_large_arc, bool is_clockwise, float end_x,
+                 float end_y, float expect_center_x, float expect_center_y,
+                 float expect_start_angle, float expect_end_angle) {
+    auto info = IGeometryBuilder::CalculateArcInfo(
+        {start_x, start_y}, {radius_x, radius_y}, angle, is_large_arc,
+        is_clockwise, {end_x, end_y});
+    REQUIRE(info.center.x == Approx(expect_center_x).margin(margin));
+    REQUIRE(info.center.y == Approx(expect_center_y).margin(margin));
+    REQUIRE(info.start_angle == Approx(expect_start_angle).margin(margin));
+    REQUIRE(info.end_angle == Approx(expect_end_angle).margin(margin));
+  };
+
+  test(1, 0, 1, 1, 0, false, true, 0, 1, 0, 0, 0, std::numbers::pi / 2);
+  test(0, 1, 1, 1, 0, false, true, -1, 0, 0, 0, std::numbers::pi / 2,
+       std::numbers::pi);
+  test(-1, 0, 1, 1, 0, false, true, 0, -1, 0, 0, std::numbers::pi,
+       -std::numbers::pi / 2);
+  test(0, -1, 1, 1, 0, false, true, 1, 0, 0, 0, -std::numbers::pi / 2, 0);
+}