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.anim;
  
  import static com.android.launcher3.util.DefaultDisplay.getSingleFrameMs;
  
  import android.content.Context;
  import android.graphics.Path;
  import android.view.animation.AccelerateDecelerateInterpolator;
  import android.view.animation.AccelerateInterpolator;
  import android.view.animation.DecelerateInterpolator;
  import android.view.animation.Interpolator;
  import android.view.animation.LinearInterpolator;
  import android.view.animation.OvershootInterpolator;
  import android.view.animation.PathInterpolator;
  
  import com.android.launcher3.Utilities;
  
  
  /**
   * Common interpolators used in Launcher
   */
  public class Interpolators {
  
      public static final Interpolator LINEAR = new LinearInterpolator();
  
      public static final Interpolator ACCEL = new AccelerateInterpolator();
      public static final Interpolator ACCEL_0_75 = new AccelerateInterpolator(0.75f);
      public static final Interpolator ACCEL_1_5 = new AccelerateInterpolator(1.5f);
      public static final Interpolator ACCEL_2 = new AccelerateInterpolator(2);
  
      public static final Interpolator DEACCEL = new DecelerateInterpolator();
      public static final Interpolator DEACCEL_1_5 = new DecelerateInterpolator(1.5f);
      public static final Interpolator DEACCEL_1_7 = new DecelerateInterpolator(1.7f);
      public static final Interpolator DEACCEL_2 = new DecelerateInterpolator(2);
      public static final Interpolator DEACCEL_2_5 = new DecelerateInterpolator(2.5f);
      public static final Interpolator DEACCEL_3 = new DecelerateInterpolator(3f);
      public static final Interpolator DEACCEL_5 = new DecelerateInterpolator(5f);
  
      public static final Interpolator ACCEL_DEACCEL = new AccelerateDecelerateInterpolator();
  
      public static final Interpolator FAST_OUT_SLOW_IN = new PathInterpolator(0.4f, 0f, 0.2f, 1f);
  
      public static final Interpolator AGGRESSIVE_EASE = new PathInterpolator(0.2f, 0f, 0f, 1f);
      public static final Interpolator AGGRESSIVE_EASE_IN_OUT = new PathInterpolator(0.6f,0, 0.4f, 1);
  
      public static final Interpolator EXAGGERATED_EASE;
  
      public static final Interpolator INSTANT = t -> 1;
  
      private static final int MIN_SETTLE_DURATION = 200;
      private static final float OVERSHOOT_FACTOR = 0.9f;
  
      static {
          Path exaggeratedEase = new Path();
          exaggeratedEase.moveTo(0, 0);
          exaggeratedEase.cubicTo(0.05f, 0f, 0.133333f, 0.08f, 0.166666f, 0.4f);
          exaggeratedEase.cubicTo(0.225f, 0.94f, 0.5f, 1f, 1f, 1f);
          EXAGGERATED_EASE = new PathInterpolator(exaggeratedEase);
      }
  
      public static final Interpolator OVERSHOOT_1_2 = new OvershootInterpolator(1.2f);
      public static final Interpolator OVERSHOOT_1_7 = new OvershootInterpolator(1.7f);
  
      public static final Interpolator TOUCH_RESPONSE_INTERPOLATOR =
              new PathInterpolator(0.3f, 0f, 0.1f, 1f);
  
      /**
       * Inversion of ZOOM_OUT, compounded with an ease-out.
       */
      public static final Interpolator ZOOM_IN = new Interpolator() {
          @Override
          public float getInterpolation(float v) {
              return DEACCEL_3.getInterpolation(1 - ZOOM_OUT.getInterpolation(1 - v));
          }
      };
  
      public static final Interpolator ZOOM_OUT = new Interpolator() {
  
          private static final float FOCAL_LENGTH = 0.35f;
  
          @Override
          public float getInterpolation(float v) {
              return zInterpolate(v);
          }
  
          /**
           * This interpolator emulates the rate at which the perceived scale of an object changes
           * as its distance from a camera increases. When this interpolator is applied to a scale
           * animation on a view, it evokes the sense that the object is shrinking due to moving away
           * from the camera.
           */
          private float zInterpolate(float input) {
              return (1.0f - FOCAL_LENGTH / (FOCAL_LENGTH + input)) /
                      (1.0f - FOCAL_LENGTH / (FOCAL_LENGTH + 1.0f));
          }
      };
  
      public static final Interpolator SCROLL = new Interpolator() {
          @Override
          public float getInterpolation(float t) {
              t -= 1.0f;
              return t*t*t*t*t + 1;
          }
      };
  
      public static final Interpolator SCROLL_CUBIC = new Interpolator() {
          @Override
          public float getInterpolation(float t) {
              t -= 1.0f;
              return t*t*t + 1;
          }
      };
  
      private static final float FAST_FLING_PX_MS = 10;
  
      public static Interpolator scrollInterpolatorForVelocity(float velocity) {
          return Math.abs(velocity) > FAST_FLING_PX_MS ? SCROLL : SCROLL_CUBIC;
      }
  
      /**
       * Create an OvershootInterpolator with tension directly related to the velocity (in px/ms).
       * @param velocity The start velocity of the animation we want to overshoot.
       */
      public static Interpolator overshootInterpolatorForVelocity(float velocity) {
          return new OvershootInterpolator(Math.min(Math.abs(velocity), 3f));
      }
  
      /**
       * Runs the given interpolator such that the entire progress is set between the given bounds.
       * That is, we set the interpolation to 0 until lowerBound and reach 1 by upperBound.
       */
      public static Interpolator clampToProgress(Interpolator interpolator, float lowerBound,
              float upperBound) {
          if (upperBound <= lowerBound) {
              throw new IllegalArgumentException(String.format(
                      "lowerBound (%f) must be less than upperBound (%f)", lowerBound, upperBound));
          }
          return t -> {
              if (t < lowerBound) {
                  return 0;
              }
              if (t > upperBound) {
                  return 1;
              }
              return interpolator.getInterpolation((t - lowerBound) / (upperBound - lowerBound));
          };
      }
  
      /**
       * Runs the given interpolator such that the interpolated value is mapped to the given range.
       * This is useful, for example, if we only use this interpolator for part of the animation,
       * such as to take over a user-controlled animation when they let go.
       */
      public static Interpolator mapToProgress(Interpolator interpolator, float lowerBound,
              float upperBound) {
          return t -> Utilities.mapRange(interpolator.getInterpolation(t), lowerBound, upperBound);
      }
  
      /**
       * Computes parameters necessary for an overshoot effect.
       */
      public static class OvershootParams {
          public Interpolator interpolator;
          public float start;
          public float end;
          public long duration;
  
          /**
           * Given the input params, sets OvershootParams variables to be used by the caller.
           * @param startProgress The progress from 0 to 1 that the overshoot starts from.
           * @param overshootPastProgress The progress from 0 to 1 where we overshoot past (should
           *        either be equal to startProgress or endProgress, depending on if we want to
           *        overshoot immediately or only once we reach the end).
           * @param endProgress The final progress from 0 to 1 that we will settle to.
           * @param velocityPxPerMs The initial velocity that causes this overshoot.
           * @param totalDistancePx The distance against which progress is calculated.
           */
          public OvershootParams(float startProgress, float overshootPastProgress,
                  float endProgress, float velocityPxPerMs, int totalDistancePx, Context context) {
              velocityPxPerMs = Math.abs(velocityPxPerMs);
              start = startProgress;
              int startPx = (int) (start * totalDistancePx);
              // Overshoot by about half a frame.
              float overshootBy = OVERSHOOT_FACTOR * velocityPxPerMs *
                      getSingleFrameMs(context) / totalDistancePx / 2;
              overshootBy = Utilities.boundToRange(overshootBy, 0.02f, 0.15f);
              end = overshootPastProgress + overshootBy;
              int endPx = (int) (end  * totalDistancePx);
              int overshootDistance = endPx - startPx;
              // Calculate deceleration necessary to reach overshoot distance.
              // Formula: velocityFinal^2 = velocityInitial^2 + 2 * acceleration * distance
              //          0 = v^2 + 2ad (velocityFinal == 0)
              //          a = v^2 / -2d
              float decelerationPxPerMs = velocityPxPerMs * velocityPxPerMs / (2 * overshootDistance);
              // Calculate time necessary to reach peak of overshoot.
              // Formula: acceleration = velocity / time
              //          time = velocity / acceleration
              duration = (long) (velocityPxPerMs / decelerationPxPerMs);
  
              // Now that we're at the top of the overshoot, need to settle back to endProgress.
              float settleDistance = end - endProgress;
              int settleDistancePx = (int) (settleDistance * totalDistancePx);
              // Calculate time necessary for the settle.
              // Formula: distance = velocityInitial * time + 1/2 * acceleration * time^2
              //          d = 1/2at^2 (velocityInitial = 0, since we just stopped at the top)
              //          t = sqrt(2d/a)
              // Above formula assumes constant acceleration. Since we use ACCEL_DEACCEL, we actually
              // have acceleration to halfway then deceleration the rest. So the formula becomes:
              //          t = sqrt(d/a) * 2 (half the distance for accel, half for deaccel)
              long settleDuration = (long) Math.sqrt(settleDistancePx / decelerationPxPerMs) * 4;
  
              settleDuration = Math.max(MIN_SETTLE_DURATION, settleDuration);
              // How much of the animation to devote to playing the overshoot (the rest is for settle).
              float overshootFraction = (float) duration / (duration + settleDuration);
              duration += settleDuration;
              // Finally, create the interpolator, composed of two interpolators: an overshoot, which
              // reaches end > 1, and then a settle to endProgress.
              Interpolator overshoot = Interpolators.clampToProgress(DEACCEL, 0, overshootFraction);
              // The settle starts at 1, where 1 is the top of the overshoot, and maps to a fraction
              // such that final progress is endProgress. For example, if we overshot to 1.1 but want
              // to end at 1, we need to map to 1/1.1.
              Interpolator settle = Interpolators.clampToProgress(Interpolators.mapToProgress(
                      ACCEL_DEACCEL, 1, (endProgress - start) / (end - start)), overshootFraction, 1);
              interpolator = t -> t <= overshootFraction
                      ? overshoot.getInterpolation(t)
                      : settle.getInterpolation(t);
          }
      }
  }
  