Purpose:
#1855

There were two issues:

• ValueOffsets was not taken into account when calculating ValueMin
• ValueOffsets was not taken into account when ensuring the base of the bar was between ValueMin and ValueMax

The second one is a little hard to explain without referencing the code, but there used to be these two lines:

valueMin = Math.Min(valueMin, ValueBase);
valueMax = Math.Max(valueMax, ValueBase);

This calculation is incorrect because the base of the bar is really ValueBase + ValueOffsets[i], so for non-zero ValueOffsets[i] you get incorrect results, such as with the following code:

double[] values = { 23, 17, 19, 24, 22 };
double[] yOffsets = { -100, -100, -100, -100, -100 }; // This is in the cookbook, but I think the better way to do this is just set ValueBase = -100. Regardless, it illustrates the issue

var bar = plt.AddBar(values);
bar.ValueOffsets = yOffsets;

Before:

Note that the axis goes from -100 to 0, as it's trying to keep ValueBase = 0 in frame, but it should be keeping ValueBase + ValueOffsets[i] = -100 in frame

After: