private static bool PreviousUnit(int start, ITextRange subrange, TomUnit unit)
{
if (subrange.Start <= start)
{
return false;
}
else
{
// collapse the range to the end and then extend it another unit.
subrange.Collapse(TomStartEnd.tomStart);
subrange.MoveStart(unit, -1);
// truncate if necessary to ensure it fits inside the range
if (subrange.Start < start)
{
subrange.Start = start;
}
return true;
}
}
private ITextRangeProvider FindAttributeBackwards(AutomationTextAttribute attribute, object val, TomUnit unit)
{
// this works just like FindAttributeForwards except we work our way backward through the range.
// we accumulate the resulting subrange with these two endpoints:
const int NoMatchYet = -1;
int start = NoMatchYet; // a character position that is extended each time we find another matching subrange.
int end = NoMatchYet; // set to a character position when we find the beginning of the match.
// examine each subrange of uniform formatting until we reach the end of our range.
// if we complete a match within the range we will break out of the middle of the loop.
int limit = _range.Start; // cache the limit of our search range.
ITextRange subrange = LastUnit(_range);
while (PreviousUnit(limit, subrange, unit))
{
// if this subrange of values has a matching attribute then add it to
// our resulting subrange.
object subrangeVal = GetAttributeValueForRange(subrange, attribute);
if (AttributeValuesAreEqual(val, subrangeVal))
{
// set the start pointer if this is the first matching subrange.
if (end == NoMatchYet)
{
end = subrange.End;
}
// update the start of the matching subrange to include the current one.
start = subrange.Start;
}
else
{
// no match.
// if we have found a matching subrange then we're done.
if (end != NoMatchYet)
{
break;
}
}
}
// if we have a matching subrange then return it, otherwise return null.
if (end != NoMatchYet)
{
subrange.SetRange(start, end);
return new WindowsRichEditRange(subrange, _pattern);
}
else
{
return null;
}
}
private static bool NextUnit(int end, ITextRange subrange, TomUnit unit)
{
if (subrange.End >= end)
{
return false;
}
else
{
// collapse the range to the end and then extend it another unit.
subrange.Collapse(TomStartEnd.tomEnd);
subrange.MoveEnd(unit, 1);
// truncate if necessary to ensure it fits inside the range
if (subrange.End > end)
{
subrange.End = end;
}
return true;
}
}
