/// <summary>
/// return a TextPointer positioned before a specified position on the line.
/// If the position exceeds the end of the line, either pad the line with
/// blanks or set the position to the last char on the line.
/// </summary>
/// <param name="Doc"></param>
/// <param name="Pointer"></param>
/// <param name="Position"></param>
/// <param name="Pad"></param>
/// <returns></returns>
public static TextPointer SetPositionOnLine(
this TextPointer Pointer,
FlowDocument Doc, int Position,
bool Pad = false)
{
TextPointer tp = Pointer.GetLineStartPosition(0);
int pos = Position;
// make sure length of the line can accomodate the position.
string lineText = Pointer.GetLineText(Doc, 0, "");
if (pos > (lineText.Length - 1))
{
if (Pad == false)
{
pos = lineText.Length - 1;
}
else
{
Pointer.PadLineToLength(Doc, pos + 1);
lineText = Pointer.GetLineText(Doc);
}
}
// position to the last char on the line.
if (lineText.Length == (pos + 1))
{
tp = Pointer.GetLineEndPosition(Doc);
}
// advance a char at a time from the start of the line.
else
{
for (int ix = 0; ix < pos; ++ix)
{
var nextTp = tp.GetNextInsertionPosition(LogicalDirection.Forward);
if (nextTp != null)
{
tp = nextTp;
}
else
{
break;
}
}
}
return(tp);
}