#80 Stacked, filled, steptype line graphs

[Kyle Centers]

When drawing a stacked filled step type graph, with the following data set:

double[,] x1 = new double[2, 8] { {0, 1, 2, 3, 4, 5, 6, 7},
{0, 0, 6, 0, 8, 0, 6, 0} };

double[,] x2 = new double[2,8] { {0, 1, 2, 3, 4, 5, 6, 7},
{0, 9, 4, 4, 3, 0, 7, 0} };

The region between (3,6), and (4,4) for ForwardStep, or (2,6) and (3,4) for RearwardStep is incorrectly filled in with the color of x2.

This Patch changes BuildPointsArray, and BuildLowPointsArray, so that the filled region is selected correctly.

[Kyle Centers]