content: /*
   * Copyright (C) 2013 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.view.animation;
  
  import android.content.Context;
  import android.content.res.Resources;
  import android.content.res.Resources.Theme;
  import android.content.res.TypedArray;
  import android.graphics.Path;
  import android.util.AttributeSet;
  import android.util.PathParser;
  import android.view.InflateException;
  
  import com.android.internal.R;
  import com.android.internal.view.animation.HasNativeInterpolator;
  import com.android.internal.view.animation.NativeInterpolatorFactory;
  import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
  
  /**
   * An interpolator that can traverse a Path that extends from <code>Point</code>
   * <code>(0, 0)</code> to <code>(1, 1)</code>. The x coordinate along the <code>Path</code>
   * is the input value and the output is the y coordinate of the line at that point.
   * This means that the Path must conform to a function <code>y = f(x)</code>.
   *
   * <p>The <code>Path</code> must not have gaps in the x direction and must not
   * loop back on itself such that there can be two points sharing the same x coordinate.
   * It is alright to have a disjoint line in the vertical direction:</p>
   * <p><blockquote><pre>
   *     Path path = new Path();
   *     path.lineTo(0.25f, 0.25f);
   *     path.moveTo(0.25f, 0.5f);
   *     path.lineTo(1f, 1f);
   * </pre></blockquote></p>
   */
  @HasNativeInterpolator
  public class PathInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
  
      // This governs how accurate the approximation of the Path is.
      private static final float PRECISION = 0.002f;
  
      private float[] mX; // x coordinates in the line
  
      private float[] mY; // y coordinates in the line
  
      /**
       * Create an interpolator for an arbitrary <code>Path</code>. The <code>Path</code>
       * must begin at <code>(0, 0)</code> and end at <code>(1, 1)</code>.
       *
       * @param path The <code>Path</code> to use to make the line representing the interpolator.
       */
      public PathInterpolator(Path path) {
          initPath(path);
      }
  
      /**
       * Create an interpolator for a quadratic Bezier curve. The end points
       * <code>(0, 0)</code> and <code>(1, 1)</code> are assumed.
       *
       * @param controlX The x coordinate of the quadratic Bezier control point.
       * @param controlY The y coordinate of the quadratic Bezier control point.
       */
      public PathInterpolator(float controlX, float controlY) {
          initQuad(controlX, controlY);
      }
  
      /**
       * Create an interpolator for a cubic Bezier curve.  The end points
       * <code>(0, 0)</code> and <code>(1, 1)</code> are assumed.
       *
       * @param controlX1 The x coordinate of the first control point of the cubic Bezier.
       * @param controlY1 The y coordinate of the first control point of the cubic Bezier.
       * @param controlX2 The x coordinate of the second control point of the cubic Bezier.
       * @param controlY2 The y coordinate of the second control point of the cubic Bezier.
       */
      public PathInterpolator(float controlX1, float controlY1, float controlX2, float controlY2) {
          initCubic(controlX1, controlY1, controlX2, controlY2);
      }
  
      public PathInterpolator(Context context, AttributeSet attrs) {
          this(context.getResources(), context.getTheme(), attrs);
      }
  
      /** @hide */
      public PathInterpolator(Resources res, Theme theme, AttributeSet attrs) {
          TypedArray a;
          if (theme != null) {
              a = theme.obtainStyledAttributes(attrs, R.styleable.PathInterpolator, 0, 0);
          } else {
              a = res.obtainAttributes(attrs, R.styleable.PathInterpolator);
          }
          parseInterpolatorFromTypeArray(a);
          setChangingConfiguration(a.getChangingConfigurations());
          a.recycle();
      }
  
      private void parseInterpolatorFromTypeArray(TypedArray a) {
          // If there is pathData defined in the xml file, then the controls points
          // will be all coming from pathData.
          if (a.hasValue(R.styleable.PathInterpolator_pathData)) {
              String pathData = a.getString(R.styleable.PathInterpolator_pathData);
              Path path = PathParser.createPathFromPathData(pathData);
              if (path == null) {
                  throw new InflateException("The path is null, which is created"
                          + " from " + pathData);
              }
              initPath(path);
          } else {
              if (!a.hasValue(R.styleable.PathInterpolator_controlX1)) {
                  throw new InflateException("pathInterpolator requires the controlX1 attribute");
              } else if (!a.hasValue(R.styleable.PathInterpolator_controlY1)) {
                  throw new InflateException("pathInterpolator requires the controlY1 attribute");
              }
              float x1 = a.getFloat(R.styleable.PathInterpolator_controlX1, 0);
              float y1 = a.getFloat(R.styleable.PathInterpolator_controlY1, 0);
  
              boolean hasX2 = a.hasValue(R.styleable.PathInterpolator_controlX2);
              boolean hasY2 = a.hasValue(R.styleable.PathInterpolator_controlY2);
  
              if (hasX2 != hasY2) {
                  throw new InflateException(
                          "pathInterpolator requires both controlX2 and controlY2 for cubic Beziers.");
              }
  
              if (!hasX2) {
                  initQuad(x1, y1);
              } else {
                  float x2 = a.getFloat(R.styleable.PathInterpolator_controlX2, 0);
                  float y2 = a.getFloat(R.styleable.PathInterpolator_controlY2, 0);
                  initCubic(x1, y1, x2, y2);
              }
          }
      }
  
      private void initQuad(float controlX, float controlY) {
          Path path = new Path();
          path.moveTo(0, 0);
          path.quadTo(controlX, controlY, 1f, 1f);
          initPath(path);
      }
  
      private void initCubic(float x1, float y1, float x2, float y2) {
          Path path = new Path();
          path.moveTo(0, 0);
          path.cubicTo(x1, y1, x2, y2, 1f, 1f);
          initPath(path);
      }
  
      private void initPath(Path path) {
          float[] pointComponents = path.approximate(PRECISION);
  
          int numPoints = pointComponents.length / 3;
          if (pointComponents[1] != 0 || pointComponents[2] != 0
                  || pointComponents[pointComponents.length - 2] != 1
                  || pointComponents[pointComponents.length - 1] != 1) {
              throw new IllegalArgumentException("The Path must start at (0,0) and end at (1,1)");
          }
  
          mX = new float[numPoints];
          mY = new float[numPoints];
          float prevX = 0;
          float prevFraction = 0;
          int componentIndex = 0;
          for (int i = 0; i < numPoints; i++) {
              float fraction = pointComponents[componentIndex++];
              float x = pointComponents[componentIndex++];
              float y = pointComponents[componentIndex++];
              if (fraction == prevFraction && x != prevX) {
                  throw new IllegalArgumentException(
                          "The Path cannot have discontinuity in the X axis.");
              }
              if (x < prevX) {
                  throw new IllegalArgumentException("The Path cannot loop back on itself.");
              }
              mX[i] = x;
              mY[i] = y;
              prevX = x;
              prevFraction = fraction;
          }
      }
  
      /**
       * Using the line in the Path in this interpolator that can be described as
       * <code>y = f(x)</code>, finds the y coordinate of the line given <code>t</code>
       * as the x coordinate. Values less than 0 will always return 0 and values greater
       * than 1 will always return 1.
       *
       * @param t Treated as the x coordinate along the line.
       * @return The y coordinate of the Path along the line where x = <code>t</code>.
       * @see Interpolator#getInterpolation(float)
       */
      @Override
      public float getInterpolation(float t) {
          if (t <= 0) {
              return 0;
          } else if (t >= 1) {
              return 1;
          }
          // Do a binary search for the correct x to interpolate between.
          int startIndex = 0;
          int endIndex = mX.length - 1;
  
          while (endIndex - startIndex > 1) {
              int midIndex = (startIndex + endIndex) / 2;
              if (t < mX[midIndex]) {
                  endIndex = midIndex;
              } else {
                  startIndex = midIndex;
              }
          }
  
          float xRange = mX[endIndex] - mX[startIndex];
          if (xRange == 0) {
              return mY[startIndex];
          }
  
          float tInRange = t - mX[startIndex];
          float fraction = tInRange / xRange;
  
          float startY = mY[startIndex];
          float endY = mY[endIndex];
          return startY + (fraction * (endY - startY));
      }
  
      /** @hide **/
      @Override
      public long createNativeInterpolator() {
          return NativeInterpolatorFactoryHelper.createPathInterpolator(mX, mY);
      }
  
  }
  