Palette tool laser prototype.

ash/common/system/chromeos/palette/tools/laser_pointer_points.h

+// Copyright 2016 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 ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_TOOLS_LASER_POINTER_POINTS_H_
+#define ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_TOOLS_LASER_POINTER_POINTS_H_
+
+#include <deque>
+#include <memory>
+#include <vector>
+
+#include "base/time/time.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace ash {
+
+// LaserPointerPoints is a helper class used for displaying the palette tool
+// laser pointer. It keeps track of the points needed to render the laser
+// pointer and its tail.
+class LaserPointerPoints {
+ public:
+  // Struct to describe each point.
+  struct LaserPoint {
+    gfx::Point location;
+    base::Time creation_time;
+  };
+
+  // Constructor with a parameter to choose the fade out time off the points in

[jdufault, 2016/08/16 19:33:56]

off => of

[sammiequon, 2016/08/16 23:18:54]

Done.

+  // the collection.
+  explicit LaserPointerPoints(base::TimeDelta life_duration);
+  ~LaserPointerPoints();
+
+  // Adds a point. Automatically clears points that are too old.
+  void AddPoint(const gfx::Point& point);
+  // Removes all points.
+  void Clear();
+  // Gets the bounding box of the points.
+  gfx::Rect GetBoundingBox() const;
+  // Returns the oldest point in the collection.
+  LaserPoint GetOldest() const;
+  // Returns the newest point in the collection.
+  LaserPoint GetMostRecent() const;
+  // Returns the number of points in the collection.
+  int GetNumberOfPoints() const;
+  // Whether there are any points or not.
+  bool IsEmpty() const;
+
+  // Expose the iterator so callers can work with the points.
+  std::deque<LaserPoint>::const_iterator PointsStart() const;
+  std::deque<LaserPoint>::const_iterator PointsEnd() const;
+
+ private:
+  // Generates extra points in an attempt to make the tail look smoother.
+  void GenerateCurvePoints(const LaserPoint& new_point,
+                           std::vector<LaserPoint>& generated_points);
+  // Computes the new cumulative bounding box of the points, after a new point
+  // |point| is added.
+  void CalculateBounds(const gfx::Point& point);
+  void ClearOldPoints();
+
+  base::TimeDelta life_duration_;
+  gfx::Rect bounds_;
+  // The collection of points.
+  std::deque<LaserPoint> points_;
+
+  DISALLOW_COPY_AND_ASSIGN(LaserPointerPoints);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_TOOLS_LASER_POINTER_POINTS_H_