lottie/src/main/java/com/airbnb/lottie/animation/content/GradientStrokeContent.java

package com.airbnb.lottie.animation.content;

import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.RadialGradient;
import android.graphics.RectF;
import android.graphics.Shader;
import androidx.annotation.Nullable;
import androidx.collection.LongSparseArray;

import com.airbnb.lottie.LottieDrawable;
import com.airbnb.lottie.animation.canvas.ICanvas;
import com.airbnb.lottie.animation.keyframe.BaseKeyframeAnimation;
import com.airbnb.lottie.animation.keyframe.MaskKeyframeAnimation;
import com.airbnb.lottie.model.content.GradientColor;
import com.airbnb.lottie.model.content.GradientStroke;
import com.airbnb.lottie.model.content.GradientType;
import com.airbnb.lottie.model.layer.BaseLayer;

public class GradientStrokeContent extends BaseStrokeContent {
  /**
   * Cache the gradients such that it runs at 30fps.
   */
  private static final int CACHE_STEPS_MS = 32;

  private final String name;
  private final LongSparseArray<LinearGradient> linearGradientCache = new LongSparseArray<>();
  private final LongSparseArray<RadialGradient> radialGradientCache = new LongSparseArray<>();
  private final RectF boundsRect = new RectF();

  private final GradientType type;
  private final int cacheSteps;
  private final BaseKeyframeAnimation<GradientColor, GradientColor> colorAnimation;
  private final BaseKeyframeAnimation<PointF, PointF> startPointAnimation;
  private final BaseKeyframeAnimation<PointF, PointF> endPointAnimation;

  public GradientStrokeContent(
      final LottieDrawable lottieDrawable, BaseLayer layer, GradientStroke stroke) {
    super(lottieDrawable, layer, stroke.getCapType().toPaintCap(),
        stroke.getJoinType().toPaintJoin(), stroke.getMiterLimit(), stroke.getOpacity(),
        stroke.getWidth(), stroke.getLineDashPattern(), stroke.getDashOffset());

    name = stroke.getName();
    type = stroke.getGradientType();
    cacheSteps = (int) (lottieDrawable.getComposition().getDuration() / CACHE_STEPS_MS);

    colorAnimation = stroke.getGradientColor().createAnimation();
    colorAnimation.addUpdateListener(this);
    layer.addAnimation(colorAnimation);

    startPointAnimation = stroke.getStartPoint().createAnimation();
    startPointAnimation.addUpdateListener(this);
    layer.addAnimation(startPointAnimation);

    endPointAnimation = stroke.getEndPoint().createAnimation();
    endPointAnimation.addUpdateListener(this);
    layer.addAnimation(endPointAnimation);
  }

  @Override public void draw(ICanvas canvas, Matrix parentMatrix, int parentAlpha, @Nullable MaskKeyframeAnimation mask, Matrix maskMatrix) {
    getBounds(boundsRect, parentMatrix);
    if (type == GradientType.Linear) {
      paint.setShader(getLinearGradient());
    } else {
      paint.setShader(getRadialGradient());
    }

    super.draw(canvas, parentMatrix, parentAlpha, mask, maskMatrix);
  }

  @Override public String getName() {
    return name;
  }

  private LinearGradient getLinearGradient() {
    int gradientHash = getGradientHash();
    LinearGradient gradient = linearGradientCache.get(gradientHash);
    if (gradient != null) {
      return gradient;
    }
    PointF startPoint = startPointAnimation.getValue();
    PointF endPoint = endPointAnimation.getValue();
    GradientColor gradientColor = colorAnimation.getValue();
    int[] colors = gradientColor.getColors();
    float[] positions = gradientColor.getPositions();
    int x0 = (int) (boundsRect.left + boundsRect.width() / 2 + startPoint.x);
    int y0 = (int) (boundsRect.top + boundsRect.height() / 2 + startPoint.y);
    int x1 = (int) (boundsRect.left + boundsRect.width() / 2 + endPoint.x);
    int y1 = (int) (boundsRect.top + boundsRect.height() / 2 + endPoint.y);
    gradient = new LinearGradient(x0, y0, x1, y1, colors, positions, Shader.TileMode.CLAMP);
    linearGradientCache.put(gradientHash, gradient);
    return gradient;
  }

  private RadialGradient getRadialGradient() {
    int gradientHash = getGradientHash();
    RadialGradient gradient = radialGradientCache.get(gradientHash);
    if (gradient != null) {
      return gradient;
    }
    PointF startPoint = startPointAnimation.getValue();
    PointF endPoint = endPointAnimation.getValue();
    GradientColor gradientColor = colorAnimation.getValue();
    int[] colors = gradientColor.getColors();
    float[] positions = gradientColor.getPositions();
    int x0 = (int) (boundsRect.left + boundsRect.width() / 2 + startPoint.x);
    int y0 = (int) (boundsRect.top + boundsRect.height() / 2 + startPoint.y);
    int x1 = (int) (boundsRect.left + boundsRect.width() / 2 + endPoint.x);
    int y1 = (int) (boundsRect.top + boundsRect.height() / 2 + endPoint.y);
    float r = (float) Math.hypot(x1 - x0, y1 - y0);
    gradient = new RadialGradient(x0, y0, r, colors, positions, Shader.TileMode.CLAMP);
    radialGradientCache.put(gradientHash, gradient);
    return gradient;
  }

  private int getGradientHash() {
    int startPointProgress = Math.round(startPointAnimation.getProgress() * cacheSteps);
    int endPointProgress = Math.round(endPointAnimation.getProgress() * cacheSteps);
    int colorProgress = Math.round(colorAnimation.getProgress() * cacheSteps);
    int hash = 17;
    if (startPointProgress != 0) {
      hash = hash * 31 * startPointProgress;
    }
    if (endPointProgress != 0) {
      hash = hash * 31 * endPointProgress;
    }
    if (colorProgress != 0) {
      hash = hash * 31 * colorProgress;
    }
    return hash;
  }
}