getAbsoluteIndexFromScreenX method
This polyline displays a given range of a data array.
x
must be given in pixels relative to dataArea's origin.
Then this function returns an absolute index between 0 and
npointsInDisplayRegion (of the original uncompressed array).
Implementation
double getAbsoluteIndexFromScreenX(int x) {
double relIx;
double absIx;
relIx = getRelativeIndexFromScreenX(x);
absIx = relIx + cpd.uIndices[0];
return absIx;
}