/// ------------------------------------------------------------------------------------
/// <summary>
/// Given a TS string and an index, find the closest start of a word before that
/// position (or after that position if at a word boundary already or in the last word
/// of the string. If in a run marked using one of the special styles, always returns
/// the position at the end of that run. Runs having these special styles are also
/// always regarded as word boundaries.
/// </summary>
/// <param name="tss">the structured string of the paragraph or translation</param>
/// <param name="ich">the given index</param>
/// <param name="specialStyles">The special styles.</param>
/// <returns>adjusted character index</returns>
/// ------------------------------------------------------------------------------------
public static int FindWordBoundary(this ITsString tss, int ich, params string[] specialStyles)
{
if (ich < 0 || ich > tss.Length)
{
throw new ArgumentOutOfRangeException("ich");
}
if (ich == 0 || ich == tss.Length)
{
return(ich);
}
string text = tss.Text;
string startingStyle = tss.StyleAt(ich);
string prevStyle = ich > 0 ? tss.StyleAt(ich - 1) : startingStyle;
if (!specialStyles.Contains(startingStyle) || prevStyle == null)
{
startingStyle = null;
}
else if (startingStyle != null)
{
startingStyle = prevStyle;
}
// Advance to the next word boundary if appropriate)
while (ich < text.Length)
{
// if the current character is space...
if (Icu.IsSeparator(text[ich]))
{
ich++;
}
else if (Icu.IsPunct(text[ich]) && ich > 0 && !Icu.IsSeparator(text[ich - 1]))
{
// if word-final punctuation advance
ich++;
}
else if (startingStyle != null && tss.StyleAt(ich) == startingStyle)
{
ich++;
}
else
{
break;
}
}
// NEVER move backward if at the end of the paragraph.
if (ich < text.Length)
{
// While the insertion point is in the middle of a word then back up to the
// start of the word or the start of a paragraph.
while (ich > 0 && !Icu.IsSeparator(text[ich - 1]) && !specialStyles.Contains(tss.StyleAt(ich - 1)))
{
ich--;
}
}
return(ich);
}