[Remoting Client] DesktopViewport Implementation

remoting/client/view_matrix.h

+// Copyright 2017 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 REMOTING_CLIENT_VIEW_MATRIX_H_
+#define REMOTING_CLIENT_VIEW_MATRIX_H_
+
+#include <array>
+
+namespace remoting {
+
+// A 2D non-skew equally scaled transformation matrix.
+// | SCALE, 0,     OFFSET_X, |
+// | 0,     SCALE, OFFSET_Y, |
+// | 0,     0,     1         |
+class ViewMatrix {
+ public:
+  struct Vector2D {
+    float x;
+    float y;
+  };
+
+  // Same as Vector2D. This alias just serves as a context hint.
+  using Point = Vector2D;
+
+  // Creates an empty matrix (0 scale and offsets).
+  ViewMatrix();
+
+  ViewMatrix(float scale, const Vector2D& offset);
+
+  ~ViewMatrix();
+
+  // Applies the matrix on the point and returns the result.
+  Point MapPoint(const Point& point) const;
+
+  // Applies the matrix on the vector and returns the result. This only scales
+  // the vector and does not apply offset.
+  Vector2D MapVector(const Vector2D& vector) const;
+
+  // Sets the scale factor, with the pivot point at (0, 0). This WON'T affect
+  // the offset.
+  void SetScale(float scale);
+
+  // Returns the scale of this matrix.
+  float GetScale() const;
+
+  // Adjust the matrix M to M' such that:
+  // M * p_a = p_b => M' * p_a = scale * (p_b - pivot) + pivot
+  void PostScale(const Point& pivot, float scale);
+
+  // Applies translation to the matrix.
+  // M * p_a = p_b => M' * p_a = p_b + delta
+  void PostTranslate(const Vector2D& delta);
+
+  // Returns the inverse of this matrix.
+  ViewMatrix Invert() const;
+
+  // Returns true if the scale and offsets are both 0.
+  bool IsEmpty() const;
+
+  // Converts to the 3x3 matrix array.
+  std::array<float, 9> ToMatrixArray() const;
+
+ private:
+  float scale_;
+  Vector2D offset_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_CLIENT_VIEW_MATRIX_H_