content: /*
   * Copyright (C) 2014 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 android.transition;
  
  import android.graphics.Rect;
  import android.transition.Slide.GravityFlag;
  import android.view.Gravity;
  import android.view.View;
  import android.view.ViewGroup;
  
  /**
   * A <code>TransitionPropagation</code> that propagates based on the distance to the side
   * and, orthogonally, the distance to epicenter. If the transitioning View is visible in
   * the start of the transition, then it will transition sooner when closer to the side and
   * later when farther. If the view is not visible in the start of the transition, then
   * it will transition later when closer to the side and sooner when farther from the edge.
   * This is the default TransitionPropagation used with {@link android.transition.Slide}.
   */
  public class SidePropagation extends VisibilityPropagation {
      private static final String TAG = "SlidePropagation";
  
      private float mPropagationSpeed = 3.0f;
      private int mSide = Gravity.BOTTOM;
  
      /**
       * Sets the side that is used to calculate the transition propagation. If the transitioning
       * View is visible in the start of the transition, then it will transition sooner when
       * closer to the side and later when farther. If the view is not visible in the start of
       * the transition, then it will transition later when closer to the side and sooner when
       * farther from the edge. The default is {@link Gravity#BOTTOM}.
       *
       * @param side The side that is used to calculate the transition propagation. Must be one of
       *             {@link Gravity#LEFT}, {@link Gravity#TOP}, {@link Gravity#RIGHT},
       *             {@link Gravity#BOTTOM}, {@link Gravity#START}, or {@link Gravity#END}.
       */
      public void setSide(@GravityFlag int side) {
          mSide = side;
      }
  
      /**
       * Sets the speed at which transition propagation happens, relative to the duration of the
       * Transition. A <code>propagationSpeed</code> of 1 means that a View centered at the side
       * set in {@link #setSide(int)} and View centered at the opposite edge will have a difference
       * in start delay of approximately the duration of the Transition. A speed of 2 means the
       * start delay difference will be approximately half of the duration of the transition. A
       * value of 0 is illegal, but negative values will invert the propagation.
       *
       * @param propagationSpeed The speed at which propagation occurs, relative to the duration
       *                         of the transition. A speed of 4 means it works 4 times as fast
       *                         as the duration of the transition. May not be 0.
       */
      public void setPropagationSpeed(float propagationSpeed) {
          if (propagationSpeed == 0) {
              throw new IllegalArgumentException("propagationSpeed may not be 0");
          }
          mPropagationSpeed = propagationSpeed;
      }
  
      @Override
      public long getStartDelay(ViewGroup sceneRoot, Transition transition,
              TransitionValues startValues, TransitionValues endValues) {
          if (startValues == null && endValues == null) {
              return 0;
          }
          int directionMultiplier = 1;
          Rect epicenter = transition.getEpicenter();
          TransitionValues positionValues;
          if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
              positionValues = startValues;
              directionMultiplier = -1;
          } else {
              positionValues = endValues;
          }
  
          int viewCenterX = getViewX(positionValues);
          int viewCenterY = getViewY(positionValues);
  
          int[] loc = new int[2];
          sceneRoot.getLocationOnScreen(loc);
          int left = loc[0] + Math.round(sceneRoot.getTranslationX());
          int top = loc[1] + Math.round(sceneRoot.getTranslationY());
          int right = left + sceneRoot.getWidth();
          int bottom = top + sceneRoot.getHeight();
  
          int epicenterX;
          int epicenterY;
          if (epicenter != null) {
              epicenterX = epicenter.centerX();
              epicenterY = epicenter.centerY();
          } else {
              epicenterX = (left + right) / 2;
              epicenterY = (top + bottom) / 2;
          }
  
          float distance = distance(sceneRoot, viewCenterX, viewCenterY, epicenterX, epicenterY,
                  left, top, right, bottom);
          float maxDistance = getMaxDistance(sceneRoot);
          float distanceFraction = distance/maxDistance;
  
          long duration = transition.getDuration();
          if (duration < 0) {
              duration = 300;
          }
  
          return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
      }
  
      private int distance(View sceneRoot, int viewX, int viewY, int epicenterX, int epicenterY,
              int left, int top, int right, int bottom) {
          final int side;
          if (mSide == Gravity.START) {
              final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
              side = isRtl ? Gravity.RIGHT : Gravity.LEFT;
          } else if (mSide == Gravity.END) {
              final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
              side = isRtl ? Gravity.LEFT : Gravity.RIGHT;
          } else {
              side = mSide;
          }
          int distance = 0;
          switch (side) {
              case Gravity.LEFT:
                  distance = right - viewX + Math.abs(epicenterY - viewY);
                  break;
              case Gravity.TOP:
                  distance = bottom - viewY + Math.abs(epicenterX - viewX);
                  break;
              case Gravity.RIGHT:
                  distance = viewX - left + Math.abs(epicenterY - viewY);
                  break;
              case Gravity.BOTTOM:
                  distance = viewY - top + Math.abs(epicenterX - viewX);
                  break;
          }
          return distance;
      }
  
      private int getMaxDistance(ViewGroup sceneRoot) {
          switch (mSide) {
              case Gravity.LEFT:
              case Gravity.RIGHT:
              case Gravity.START:
              case Gravity.END:
                  return sceneRoot.getWidth();
              default:
                  return sceneRoot.getHeight();
          }
      }
  }
  