DrawPolygon class with Unit Tests

cc/quads/draw_polygon.h

+// Copyright 2014 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 CC_QUADS_DRAW_POLYGON_H_
+#define CC_QUADS_DRAW_POLYGON_H_
+
+#include <vector>
+
+#include "cc/base/math_util.h"
+#include "cc/output/bsp_compare_result.h"
+#include "cc/quads/draw_quad.h"
+#include "ui/gfx/point3_f.h"
+#include "ui/gfx/quad_f.h"
+#include "ui/gfx/vector3d_f.h"
+
+namespace cc {
+
+class CC_EXPORT DrawPolygon {
+ public:
+  DrawPolygon();
+  ~DrawPolygon();
+
+  DrawPolygon(DrawQuad* original_ref,
+              const std::vector<gfx::Point3F>& in_points,
+              const gfx::Vector3dF& normal,
+              int draw_order_index = 0);
+
+  // Split takes this DrawPolygon and splits it into two pieces that are on
+  // either side of |splitter|. Any edges of this polygon that cross the plane
+  // of |splitter| will have an intersection point that is shared by both
+  // polygons on either side.
+  // Split will only return true if it determines that we got back 2
+  // intersection points. Only when it returns true will front and back both be
+  // valid new polygons that are on opposite sides of the splitting plane.
+  bool Split(const DrawPolygon& splitter,
+             scoped_ptr<DrawPolygon>* front,
+             scoped_ptr<DrawPolygon>* back);
+  float SignedPointDistance(const gfx::Point3F& point) const;
+  // Checks polygon a against polygon b and returns which side it lies on, or
+  // whether it crosses (necessitating a split in the BSP tree).
+  static BspCompareResult SideCompare(const DrawPolygon& a,
+                                      const DrawPolygon& b);
+  void ToQuads2D(std::vector<gfx::QuadF>* quads) const;
+  void TransformToScreenSpace(const gfx::Transform& transform);
+  void TransformToLayerSpace(const gfx::Transform& inverse_transform);
+
+  const std::vector<gfx::Point3F>& points() const { return points_; }
+  const gfx::Vector3dF& normal() const { return normal_; }
+  const DrawQuad* original_ref() const { return original_ref_; }
+  int order_index() const { return order_index_; }
+
+  scoped_ptr<DrawPolygon> CreateCopy();
+
+  static gfx::Vector3dF default_normal;
+
+ private:
+  void ApplyTransform(const gfx::Transform& transform);
+  void ApplyTransformToNormal(const gfx::Transform& transform);
+
+  std::vector<gfx::Point3F> points_;
+  // Normalized, necessitated by distance calculations and tests of coplanarity.
+  gfx::Vector3dF normal_;
+  // This is an index that can be used to test whether a quad comes before or
+  // after another in document order, useful for tie-breaking when it comes
+  // to coplanar surfaces.
+  int order_index_;
+  // The pointer to the original quad, which gives us all the drawing info
+  // we need.
+  // This DrawQuad is owned by the caller and its lifetime must be preserved
+  // as long as this DrawPolygon is alive.
+  DrawQuad* original_ref_;
+};
+
+}  // namespace cc
+
+#endif  // CC_QUADS_DRAW_POLYGON_H_