private void MergeTextChangeRight(TextChange oldChange, TextChange newChange, int offset, int length)
{
// If the old change is an addition, find the length of the overlap
// and adjust the addition and new deletion counts accordingly
int addedLengthOverlap = oldChange.AddedLength > 0 ? offset + length - oldChange.Offset : 0;
#if PROPERTY_CHANGES
// Check for a property change in the new change that overlaps the old change
int propertyOverlap = newChange.Offset + newChange.PropertyCount - oldChange.Offset;
if (propertyOverlap > 0)
{
int delta = Math.Min(propertyOverlap, addedLengthOverlap);
newChange.SetPropertyCount(newChange.PropertyCount - delta);
// Don't need to adjust oldChange.PropertyCount, since oldChange is about to be removed
}
#endif
// adjust removed count
if (addedLengthOverlap >= oldChange.AddedLength)
{
// old change is entirely within new one
newChange.RemovedLength += (oldChange.RemovedLength - oldChange.AddedLength);
Changes.Remove(oldChange.Offset);
}
else
{
newChange.RemovedLength += (oldChange.RemovedLength - addedLengthOverlap);
newChange.AddedLength += (oldChange.AddedLength - addedLengthOverlap);
Changes.Remove(oldChange.Offset);
}
}
private bool MergePropertyChange(TextChange leftChange, TextChange rightChange)
{
if (leftChange.Offset + leftChange.PropertyCount >= rightChange.Offset)
{
if (leftChange.Offset + leftChange.PropertyCount < rightChange.Offset + rightChange.PropertyCount)
{
// right change is partially inside left, but not completely.
int overlap = leftChange.Offset + leftChange.PropertyCount - rightChange.Offset;
int delta = rightChange.PropertyCount - overlap;
leftChange.SetPropertyCount(leftChange.PropertyCount + delta);
}
rightChange.SetPropertyCount(0);
return true;
}
return false;
}
// returns true if the change merged into an earlier insertion
private bool MergeTextChangeLeft(TextChange oldChange, TextChange newChange, bool isDeletion, int length)
{
// newChange is inserting or deleting text inside oldChange.
int overlap;
#if PROPERTY_CHANGES
// Check for a property change in the old change that overlaps the new change
if (oldChange.Offset + oldChange.PropertyCount >= newChange.Offset)
{
if (isDeletion)
{
overlap = oldChange.PropertyCount - (newChange.Offset - oldChange.Offset);
oldChange.SetPropertyCount(oldChange.PropertyCount - Math.Min(overlap, length));
DeleteChangeIfEmpty(oldChange);
}
else
{
oldChange.SetPropertyCount(oldChange.PropertyCount + length);
}
}
#endif
if (oldChange.Offset + oldChange.AddedLength >= newChange.Offset)
{
// If any text was deleted in the new change, adjust the added count of the
// previous change accordingly. The removed count of the new change must be
// adjusted by the same amount.
if (isDeletion)
{
overlap = oldChange.AddedLength - (newChange.Offset - oldChange.Offset);
int cancelledCount = Math.Min(overlap, newChange.RemovedLength);
oldChange.AddedLength -= cancelledCount;
oldChange.RemovedLength += (length - cancelledCount);
}
else
{
oldChange.AddedLength += length;
}
#if PROPERTY_CHANGES
if (newChange.PropertyCount == 0)
{
// We've merged the data from the new change into an older one, so we can
// delete the change from the list.
Changes.Remove(newChange.Offset);
}
else
{
// Can't delete the change, since there's pre-existing property change data, so
// just clear the data instead.
newChange.AddedLength = 0;
newChange.RemovedLength = 0;
}
#else
// We've merged the data from the new change into an older one, so we can
// delete the change from the list.
Changes.Remove(newChange.Offset);
#endif
return true;
}
return false;
}