ui/gfx/animation/tween.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_ANIMATION_TWEEN_H_
#define UI_GFX_ANIMATION_TWEEN_H_

#include "base/basictypes.h"
#include "third_party/skia/include/core/SkColor.h"
#include "ui/gfx/gfx_export.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/transform.h"

namespace gfx {

class GFX_EXPORT Tween {
 public:
  enum Type {
    LINEAR,             // Linear.
    EASE_OUT,           // Fast in, slow out (default).
    EASE_IN,            // Slow in, fast out.
    EASE_IN_2,          // Variant of EASE_IN that starts out slower than
                        // EASE_IN.
    EASE_IN_OUT,        // Slow in and out, fast in the middle.
    FAST_IN_OUT,        // Fast in and out, slow in the middle.
    EASE_OUT_SNAP,      // Fast in, slow out, snap to final value.
    SMOOTH_IN_OUT,      // Smooth, consistent speeds in and out (sine wave).
    FAST_OUT_SLOW_IN,   // Variant of EASE_IN_OUT which should be used in most
                        // cases.
    LINEAR_OUT_SLOW_IN, // Variant of EASE_OUT which should be used for
                        // fading in from 0% or motion when entering a scene.
    FAST_OUT_LINEAR_IN, // Variant of EASE_IN which should should be used for
                        // fading out to 0% or motion when exiting a scene.
    ZERO,               // Returns a value of 0 always.
  };

  // Returns the value based on the tween type. |state| is from 0-1.
  static double CalculateValue(Type type, double state);

  // Conveniences for getting a value between a start and end point.
  static SkColor ColorValueBetween(double value, SkColor start, SkColor target);
  static double DoubleValueBetween(double value, double start, double target);
  static float FloatValueBetween(double value, float start, float target);

  // Interpolated between start and target, with every integer in this range
  // given equal weight.
  static int IntValueBetween(double value, int start, int target);

  // Interpolates between start and target as real numbers, and rounds the
  // result to the nearest integer, with ties broken by rounding towards
  // positive infinity. This gives start and target half the weight of the
  // other integers in the range. This is the integer interpolation approach
  // specified by www.w3.org/TR/css3-transitions.
  static int LinearIntValueBetween(double value, int start, int target);
  static gfx::Rect RectValueBetween(double value,
                                    const gfx::Rect& start_bounds,
                                    const gfx::Rect& target_bounds);
  static gfx::Transform TransformValueBetween(
      double value,
      const gfx::Transform& start_transform,
      const gfx::Transform& target_transform);

 private:
  Tween();
  ~Tween();

  DISALLOW_COPY_AND_ASSIGN(Tween);
};

}  // namespace gfx

#endif  // UI_GFX_ANIMATION_TWEEN_H_