app/tween.cc

// Copyright (c) 2010 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.

#include "app/tween.h"

#include <math.h>

#if defined(OS_WIN)
#include <float.h>
#endif

#include "base/logging.h"
#include "gfx/rect.h"

// static
double Tween::CalculateValue(Tween::Type type, double state) {
  DCHECK_GE(state, 0);
  DCHECK_LE(state, 1);

  switch (type) {
    case EASE_IN:
      return pow(state, 2);

    case EASE_IN_OUT:
      if (state < 0.5)
        return pow(state * 2, 2) / 2.0;
      return 1.0 - (pow((state - 1.0) * 2, 2) / 2.0);

    case FAST_IN_OUT:
      return (pow(state - 0.5, 3) + 0.125) / 0.25;

    case LINEAR:
      return state;

    case EASE_OUT_SNAP:
      state = 0.95 * (1.0 - pow(1.0 - state, 2));
      break;

    case EASE_OUT:
      return 1.0 - pow(1.0 - state, 2);

    case ZERO:
      return 0;
  }

  NOTREACHED();
  return state;
}

// static
double Tween::ValueBetween(double value, double start, double target) {
  return start + (target - start) * value;
}

// static
int Tween::ValueBetween(double value, int start, int target) {
  if (start == target)
    return start;
  double delta = static_cast<double>(target - start);
  if (delta < 0)
    delta--;
  else
    delta++;
#if defined(OS_WIN)
  return start + static_cast<int>(value * _nextafter(delta, 0));
#else
  return start + static_cast<int>(value * nextafter(delta, 0));
#endif
}

// static
gfx::Rect Tween::ValueBetween(double value,
                              const gfx::Rect& start_bounds,
                              const gfx::Rect& target_bounds) {
  return gfx::Rect(ValueBetween(value, start_bounds.x(), target_bounds.x()),
                   ValueBetween(value, start_bounds.y(), target_bounds.y()),
                   ValueBetween(value, start_bounds.width(),
                                target_bounds.width()),
                   ValueBetween(value, start_bounds.height(),
                                target_bounds.height()));
}