Hi Jack,
As ChartDirector is a charting problem, the line it draws is based on your data points. If
you want to draw lines and arcs, first, make sure your data points line on the lines and
arcs, then join them together using a suitable method. If your data points are dense,
you just join them with straight lines (addLineLayer). If your data points are sparse, you
can join them with spline curves. In this case, to keep the straight line straight, you can
insert additional end points.
I have attached an example, which is just a simple spline curve, but with some data
that represent curves and straight lines. The code is as follows:
doubel dataY[] = {32, 32, 39, 39, 23, 23, 41, 30, 30, 26, 26, 35, 29};
double dataX[] = {1, 1, 2, 2, 3, 4.1, 5, 5.5, 5.5, 7.5, 7.5, 8, 9};
int pointCount = (int)(sizeof(dataX) / sizeof(dataX[0]));
XYChart *c = new XYChart(600, 300);
c->setPlotArea(55, 20, 520, 235, 0xffffff, -1, 0xcccccc, 0xcccccc, 0xcccccc);
SplineLayer *layer = c->addSplineLayer();
layer->setLineWidth(2);
layer->addDataSet(DoubleArray(dataY, pointCount), 0x0000c0)->
setDataSymbol(Chart::CircleSymbol, 9, 0xffff00);
layer->setXData(DoubleArray(dataX, pointCount));
c->makeChart("c:\\\\test.png");
Regards
Peter Kwan
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(Peter Kwan) 
How can I draw lines and arcs ？