private async Task <SnapshotSpan> GetChangedSpanAsync(
Document currentDocument, ITextSnapshot currentSnapshot, CancellationToken cancellationToken)
{
// We don't need to grab _lastProcessedDocument in a lock. We don't care which version of the previous
// doc we grab, just that we grab some prior version. This is only used to narrow down the changed range we
// specify, so it's ok if it's slightly larger because we read in a change from a couple of edits ago.
var previousDocument = _lastProcessedDocument;
if (previousDocument != null)
{
var service = TryGetClassificationService(currentSnapshot);
if (service != null)
{
var changeRange = await service.ComputeSyntacticChangeRangeAsync(
previousDocument, currentDocument, _diffTimeout, cancellationToken).ConfigureAwait(false);
if (changeRange != null)
{
return(currentSnapshot.GetSpan(changeRange.Value.Span.Start, changeRange.Value.NewLength));
}
}
}
// Couldn't compute a narrower range. Just the mark the entire file as changed.
return(currentSnapshot.GetFullSpan());
}
private ClassificationSpan ClassificationSpanFor(Token token, ITextSnapshot textBuffer, int offset)
{
var textSpan = textBuffer.GetSpan(offset + token.Begin, token.End - token.Begin);
return(new ClassificationSpan(ClassificationFor(token, textSpan), textSpan));
}
public static TextSpan GetSpan(this ITextSnapshot snapshot, Span span)
{
return(snapshot.GetSpan(span.Start, span.Length));
}
public static SnapshotSpan GetFullSpan(this ITextSnapshot snapshot)
{
return(snapshot.GetSpan(0, snapshot.Length));
}
private ClassificationSpan ClassificationSpanFor(Token token, ITextSnapshot textBuffer, int offset)
{
var textSpan = textBuffer.GetSpan(offset + token.Begin, token.End - token.Begin);
return new ClassificationSpan(ClassificationFor(token, textSpan), textSpan);
}