Add Vector2d classes that represent offsets, instead of using Point.

ui/gfx/vector2d.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.
+
+// Defines a simple integer vector class.  This class is used to indicate a
+// distance in two dimensions between two points. Subtracting two points should
+// produce a vector, and adding a vector to a point produces the point at the
+// vector's distance from the original point.
+
+#ifndef UI_GFX_VECTOR2D_H_
+#define UI_GFX_VECTOR2D_H_
+
+#include <string>
+
+#include "base/basictypes.h"

[Peter Kasting, 2012/10/30 20:24:37]

How come this file includes this but vector2d_f.h doesn't?

[danakj, 2012/10/30 21:14:53]

For LengthSquared to return int64.

+#include "ui/base/ui_export.h"
+#include "ui/gfx/vector2d_f.h"
+
+namespace gfx {
+
+class UI_EXPORT Vector2d {
+ public:
+  Vector2d();
+  Vector2d(int x, int y);
+
+  int x() const { return x_; }
+  void set_x(int x) { x_ = x; }
+
+  int y() const { return y_; }
+  void set_y(int y) { y_ = y; }
+
+  // True if both components of the vector are 0.
+  bool IsZero() const;
+
+  // Adds |x| and |y| to the x-axis and y-axis components respectively.
+  void Grow(int x, int y);
+
+  // Add the components of the |other| vector to the current vector.
+  void Add(const Vector2d& other);
+  // Subtract the components of the |other| vector from the current vector.
+  void Subtract(const Vector2d& other);
+
+  void operator+=(const Vector2d& other) { Add(other); }
+  void operator-=(const Vector2d& other) { Subtract(other); }
+
+  // Gives the square of the diagonal length of the vector. Since this is
+  // cheaper to compute than Length(), it is useful when you want to compare
+  // relative lengths of different vectors without needing the actual lengths.
+  int64 LengthSquared() const;
+  // Gives the diagonal length of the vector.
+  float Length() const;
+
+  std::string ToString() const;
+
+  operator Vector2dF() const { return Vector2dF(x_, y_); }
+
+ private:
+  int x_;
+  int y_;
+};
+
+inline bool operator==(const Vector2d& lhs, const Vector2d& rhs) {
+  return lhs.x() == rhs.x() && lhs.y() == rhs.y();
+}
+
+inline Vector2d operator-(const Vector2d& v) {
+  return Vector2d(-v.x(), -v.y());
+}
+
+inline Vector2d operator+(const Vector2d& lhs, const Vector2d& rhs) {
+  Vector2d result = lhs;
+  result.Add(rhs);
+  return result;
+}
+
+inline Vector2d operator-(const Vector2d& lhs, const Vector2d& rhs) {
+  Vector2d result = lhs;
+  result.Add(-rhs);
+  return result;
+}
+
+}  // namespace gfx
+
+#endif // UI_GFX_VECTOR2D_H_