Short line intersection

Consider a strategy which finds intersection point of two short lines and then plots a signal chart object on each of those intersections.

    class PointDbl {
        public final double x;
        public final double y;        
        public PointDbl(double x, double y){
            this.x = x;
            this.y = y;
        }
    }

    @Override
    public void onStart(IContext context) throws JFException {
        history = context.getHistory();
        console = context.getConsole();
        chart = context.getChart(instrument);
        if(chart == null){
            console.getErr().println("No chart opened, can't plot lines");
            context.stop();
        }

        IBar bar1 = history.getBar(instrument, period, side, 1);
        IBar bar10 = history.getBar(instrument, period, side, 10);
        IShortLineChartObject line1 = chart.getChartObjectFactory().createShortLine("line1", 
                bar1.getTime(), bar1.getHigh(), bar10.getTime(), bar10.getLow()
        );
        IShortLineChartObject line2 = chart.getChartObjectFactory().createShortLine("line2", 
                bar1.getTime(), bar1.getLow(), bar10.getTime(), bar10.getHigh()
        );
        chart.add(line1);
        chart.add(line2);
        PointDbl point = intersection( 
                line1.getTime(0), line1.getPrice(0), 
                line1.getTime(1), line1.getPrice(1), 

                line2.getTime(0), line2.getPrice(0), 
                line2.getTime(1), line2.getPrice(1) 
                );
        if(point == null){
            console.getOut().println("Lines don't intersect");
        } else {
            console.getOut().println(String.format(
                    "Lines intersect at %s:%.5f ",DateUtils.format(point.x), point.y));
            ISignalDownChartObject signalArr = 
                    chart.getChartObjectFactory().createSignalDown(
                            "intersection_point",
                            (long)point.x + period.getInterval()/2, point.y);
            signalArr.setStickToCandleTimeEnabled(false);
            chart.add(signalArr);
        }

    }

    public PointDbl intersection(
            double x1, double y1, double x2, double y2, 
            double x3, double y3, double x4, double y4
        ) {
        double d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
        if (d == 0)
            return null;

        double xi = ((x3 - x4) * (x1 * y2 - y1 * x2) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d;
        double yi = ((y3 - y4) * (x1 * y2 - y1 * x2) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d;

        return new PointDbl(xi, yi);
    }

IntersectionPoint.java

Indicator output line intersection

Consider a strategy which finds indicator two indicator output line intersection points by using a geometric method. It also plots a signal chart object on each of those intersections.

//..

    @Override
    public void onStart(IContext context) throws JFException {
        history = context.getHistory();
        console = context.getConsole();
        indicators = context.getIndicators();

        chart = context.getChart(instrument);
        if(chart == null){
            console.getErr().println("No chart opened, can't plot indicators.");
            context.stop();
        }
        if(chart.getSelectedPeriod() != period || chart.getSelectedOfferSide() != side){
            console.getErr().println("Chart feed does not match the one of indicators. Can't plot indicators.");
            context.stop();
        }
        chart.add(indicators.getIndicator("SMA"), new Object [] {smaPeriod1});
        chart.add(indicators.getIndicator("SMA"), new Object [] {smaPeriod2});

        IBar bar = history.getBar(instrument, period, side, toShift);
        double[] sma1 = indicators.sma(
                instrument, period, side, AppliedPrice.CLOSE, smaPeriod1, chart.getFilter(),
                fromShift, bar.getTime(), 0);
        double[] sma2 = indicators.sma(
                instrument, period, side, AppliedPrice.CLOSE, smaPeriod2, chart.getFilter(),
                fromShift, bar.getTime(), 0);
        IBar[] bars = history.getBars(
                instrument, period, side, chart.getFilter(),
                fromShift, bar.getTime(), 0).toArray(new IBar[] {});
        for(int i=0; i< sma1.length - 1; i++){
            PointDbl point = intersection( 
                    bars[i].getTime(), sma1[i], bars[i+1].getTime(), sma1[i+1], 
                    bars[i].getTime(), sma2[i], bars[i+1].getTime(), sma2[i+1]
                    );
            long intersectTime = (long)point.x;
            if(point == null || intersectTime < bars[i].getTime() || intersectTime > bars[i+1].getTime()){
                console.getOut().println(
                        "Lines don't intersect between " +
                                DateUtils.format(bars[i].getTime()) + " and " +
                                DateUtils.format(bars[i+1].getTime()));
            } else {
                console.getOut().println(String.format(
                        "Lines intersect at %s:%.5f ",
                        DateUtils.format(point.x), point.y));
                ISignalDownChartObject signalArr =
                        chart.getChartObjectFactory().createSignalDown(
                            "intersection_point"+i, (long)point.x + period.getInterval()/2, point.y);
                signalArr.setStickToCandleTimeEnabled(false);
                chart.add(signalArr);
            }
        }
    }

//..

IntersectionPointInd.java