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CGMutablePathRef path = CGPathCreateMutable();
CGPathAddLines(path, &CGAffineTransformIdentity, points, sizeof points / sizeof *points);

CGMutablePathRef dotPath = CGPathCreateMutable();
for(NSInteger i = 0; i < [data.values count]; i++) {
    CGRect rect = CGRectMake(points[i].x - data.dotRadius, points[i].y - data.dotRadius, data.dotRadius * 2, data.dotRadius * 2);
    CGPathAddEllipseInRect(dotPath, &CGAffineTransformIdentity, rect);
    CGPathAddEllipseInRect(dotPath, &CGAffineTransformIdentity, CGRectInset(rect, data.lineWidth, data.lineWidth));
}
CGPathAddPath(path, &CGAffineTransformIdentity, dotPath);

CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddRect(maskPath, &CGAffineTransformIdentity, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));
CGPathAddPath(maskPath, &CGAffineTransformIdentity, dotPath);


CAShapeLayer *layer = self.layers[line];
layer.path = strokePath;
layer.lineWidth = 2;
layer.strokeColor = data.lineColor.CGColor;
layer.fillColor = nil;
layer.fillRule = kCAFillRuleEvenOdd;

CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.path = maskPath;
maskLayer.fillRule = kCAFillRuleEvenOdd;
layer.mask = maskLayer;

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