...

3 files changed, 22 insertions, 2 deletions

diff --git a/include/cru/platform/Matrix.hpp b/include/cru/platform/Matrix.hpp
index 7985af0e..72459b79 100644
--- a/include/cru/platform/Matrix.hpp
+++ b/include/cru/platform/Matrix.hpp
@@ -2,6 +2,7 @@
 #include "GraphicsBase.hpp"
 
 #include <cmath>
+#include <optional>
 
 namespace cru::platform {
 struct Matrix {
@@ -80,6 +81,18 @@ struct Matrix {
                   a.m31 * b.m12 + a.m32 * b.m22 + b.m32};
   }
 
+  std::optional<Matrix> Inverted() const {
+    if (m11 * m22 == m12 * m21) return std::nullopt;
+    Matrix result;
+    result.m11 = m22 / (m11 * m22 - m12 * m21);
+    result.m12 = m12 / (m12 * m21 - m11 * m22);
+    result.m21 = m21 / (m12 * m21 - m11 * m22);
+    result.m22 = m11 / (m11 * m22 - m12 * m21);
+    result.m31 = (m21 * m32 - m22 * m31) / (m11 * m22 - m12 * m21);
+    result.m32 = (m31 * m12 - m11 * m32) / (m11 * m22 - m12 * m21);
+    return result;
+  }
+
  private:
   static constexpr float PI = 3.1415926535f;
 
diff --git a/include/cru/platform/graphics/Painter.hpp b/include/cru/platform/graphics/Painter.hpp
index 24592f95..9bde0640 100644
--- a/include/cru/platform/graphics/Painter.hpp
+++ b/include/cru/platform/graphics/Painter.hpp
@@ -7,6 +7,8 @@ struct IPainter : virtual IPlatformResource {
   virtual Matrix GetTransform() = 0;
   virtual void SetTransform(const Matrix& matrix) = 0;
 
+  virtual void ConcatTransform(const Matrix& matrix) = 0;
+
   virtual void Clear(const Color& color) = 0;
 
   virtual void DrawLine(const Point& start, const Point& end, IBrush* brush,
@@ -26,6 +28,10 @@ struct IPainter : virtual IPlatformResource {
 
   virtual void PopLayer() = 0;
 
+  virtual void PushState() = 0;
+
+  virtual void PopState() = 0;
+
   virtual void EndDraw() = 0;
 };
 }  // namespace cru::platform::graphics
diff --git a/include/cru/platform/graphics/util/Painter.hpp b/include/cru/platform/graphics/util/Painter.hpp
index 90457cf4..2e0fbb51 100644
--- a/include/cru/platform/graphics/util/Painter.hpp
+++ b/include/cru/platform/graphics/util/Painter.hpp
@@ -10,8 +10,9 @@ void WithTransform(IPainter* painter, const Matrix& matrix, const Fn& action) {
   static_assert(std::is_invocable_v<decltype(action), IPainter*>,
                 "Action must can be be invoked with painter.");
   const auto old = painter->GetTransform();
-  painter->SetTransform(matrix * old);
+  painter->PushState();
+  painter->ConcatTransform(matrix);
   action(painter);
-  painter->SetTransform(old);
+  painter->PopState();
 }
 }  // namespace cru::platform::graphics::util