// Try to parse the change incrementally
// Partial Parsing succeeds if:
// * A single span can be identified which owns the change (i.e. it doesn't overlap multiple spans)
// * The span which owns the change has logic to accept it
// The performance of this method is crucial, since it occurs on the caller's thread (usually a UI thread).
private PartialParseResult TryPartialParse(TextChange change) {
PartialParseResult result = PartialParseResult.Rejected;
if (CurrentParseTree != null && !_parseUnderway) {
// Try the last change owner
if (_lastChangeOwner != null && _lastChangeOwner.OwnsChange(change)) {
result = _lastChangeOwner.ApplyChange(change);
// If the last change was provisional, then the result of this span's attempt to parse partially goes
// Otherwise, accept the change if this span accepted it, but if it didn't, just do the standard search.
if (LastResultProvisional || result.HasFlag(PartialParseResult.Accepted)) {
return result;
}
}
// Locate the span responsible for this change
_lastChangeOwner = CurrentParseTree.LocateOwner(change);
if (LastResultProvisional) {
// Last change owner couldn't accept this, so we must do a full reparse
result = PartialParseResult.Rejected;
}
else if (_lastChangeOwner != null) {
result = _lastChangeOwner.ApplyChange(change);
if (result.HasFlag(PartialParseResult.AutoCompleteBlock)) {
_lastAutoCompleteSpan = _lastChangeOwner;
}
}
}
return result;
}
