private void UpdateRange(double scroll, long scrollLinesPossible, bool scrollToEnd)
{
Extent newExtent = lineRange.RelExtent(scrollLinesPossible);
if (scrollToEnd)
{
UpdateRange(-1, Origin.End, Origin.End);
}
else if (newExtent != null)
{
UpdateRange(newExtent.Begin, Origin.Begin, Origin.Begin);
}
else
{
int linesOnScreen = FullyVisibleLines;
double lineLen = (double)(lineRange.LastExtent.End - lineRange.FirstExtent.Begin) / lineRange.ExtentsCount;
double vis = linesOnScreen * lineLen;
double streamLenMod = lineRange.StreamLength - vis;
long pos;
Origin origin;
double sValue = scrollPosition ?? 0.5; // 0.5: No correction
double cFactor = 1 - sValue * (1 - sValue) * 4;
if (sValue <= 0.5)
{
origin = Origin.Begin;
pos = ToRange(RoundToLongRange(LineAt(0).Begin + streamLenMod * scroll), 0, lineRange.StreamLength - 1);
long p = RoundToLongRange(cFactor * (sValue * streamLenMod - pos));
pos = ToRange(pos + p, 0, lineRange.StreamLength - 1); // Position at the begin of the line
pos += Round(sValue * lineLen); // Position within the line
}
else
{
origin = Origin.End;
pos = ToRange(RoundToLongRange(LineAt(linesOnScreen - 1).End + streamLenMod * scroll), 0, lineRange.StreamLength);
long p = RoundToLongRange(cFactor * ((lineRange.StreamLength - (1 - sValue) * streamLenMod) - pos));
pos = ToRange(pos + p, 0, lineRange.StreamLength); // Position at the end of the line
pos -= lineRange.StreamLength + 1; // --> From the end of the stream
pos -= Round((1 - sValue) * lineLen); // Position within the line
}
UpdateRange(pos, origin, Origin.Begin);
}
}
