Splitting of layers for correct intersections

ui/gfx/geometry/quad_f.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_GEOMETRY_QUAD_F_H_
 #define UI_GFX_GEOMETRY_QUAD_F_H_
 
 #include <algorithm>
 #include <cmath>
 #include <iosfwd>
@@ skipping 49 matching lines @@
   // the quad may lie on the right/bottom edge of the resulting rectangle,
   // rather than being strictly inside it.
   RectF BoundingBox() const {
     float rl = std::min(std::min(p1_.x(), p2_.x()), std::min(p3_.x(), p4_.x()));
     float rr = std::max(std::max(p1_.x(), p2_.x()), std::max(p3_.x(), p4_.x()));
     float rt = std::min(std::min(p1_.y(), p2_.y()), std::min(p3_.y(), p4_.y()));
     float rb = std::max(std::max(p1_.y(), p2_.y()), std::max(p3_.y(), p4_.y()));
     return RectF(rl, rt, rr - rl, rb - rt);
   }
 
+  // Realigns the corners in the quad by rotating them n corners to the right.
+  void Realign(size_t times) {
+    for (size_t i = 0; i < times % 4; ++i) {
+      PointF temp = p1_;
+      p1_ = p2_;
+      p2_ = p3_;
+      p3_ = p4_;
+      p4_ = temp;
+    }
+  }
+
   // Add a vector to the quad, offseting each point in the quad by the vector.
   void operator+=(const Vector2dF& rhs);
   // Subtract a vector from the quad, offseting each point in the quad by the
   // inverse of the vector.
   void operator-=(const Vector2dF& rhs);
 
   // Scale each point in the quad by the |scale| factor.
   void Scale(float scale) { Scale(scale, scale); }
 
   // Scale each point in the quad by the scale factors along each axis.
@@ skipping 26 matching lines @@
 GFX_EXPORT QuadF operator-(const QuadF& lhs, const Vector2dF& rhs);
 
 // This is declared here for use in gtest-based unit tests but is defined in
 // the gfx_test_support target. Depend on that to use this in your unit test.
 // This should not be used in production code - call ToString() instead.
 void PrintTo(const QuadF& quad, ::std::ostream* os);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_QUAD_F_H_