/// <summary>
/// return the location on the text line of the specified coordinate point within
/// the RichTextBox.
/// </summary>
/// <param name="TextBox"></param>
/// <param name="Point"></param>
/// <returns></returns>
public static Tuple <TextPointer, int, int> GetLocationFromPoint(
this RichTextBox TextBox, Point Point)
{
TextPointer tp = TextBox.GetPositionFromPoint(Point, true);
var px = tp.GetPositionInLine();
if (px > 0)
{
px = px - 1;
}
var lineBx = tp.GetLineNumber(TextBox.Document);
return(new Tuple <TextPointer, int, int>(tp, lineBx, px));
}