content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.android.launcher3.touch;
  
  /**
   * Utility methods for overscroll damping and related effect.
   */
  public class OverScroll {
  
      private static final float OVERSCROLL_DAMP_FACTOR = 0.07f;
  
      /**
       * This curve determines how the effect of scrolling over the limits of the page diminishes
       * as the user pulls further and further from the bounds
       *
       * @param f The percentage of how much the user has overscrolled.
       * @return A transformed percentage based on the influence curve.
       */
      private static float overScrollInfluenceCurve(float f) {
          f -= 1.0f;
          return f * f * f + 1.0f;
      }
  
      /**
       * @param amount The original amount overscrolled.
       * @param max The maximum amount that the View can overscroll.
       * @return The dampened overscroll amount.
       */
      public static int dampedScroll(float amount, int max) {
          if (Float.compare(amount, 0) == 0) return 0;
  
          float f = amount / max;
          f = f / (Math.abs(f)) * (overScrollInfluenceCurve(Math.abs(f)));
  
          // Clamp this factor, f, to -1 < f < 1
          if (Math.abs(f) >= 1) {
              f /= Math.abs(f);
          }
  
          return Math.round(OVERSCROLL_DAMP_FACTOR * f * max);
      }
  }
  