public static StrokeTag tag(this Stroke stroke, StrokeTag tag)
 {
     stroke.AddPropertyData(STROKE_TAG_GUID, tag.author);
     var privacy = Privacy.Private;
     if (tag.privacy != Privacy.NotSet)
         privacy = tag.privacy;
     stroke.AddPropertyData(STROKE_IDENTITY_GUID, tag.id);
     stroke.AddPropertyData(STROKE_PRIVACY_GUID, privacy.ToString());
     stroke.AddPropertyData(STARTINGCHECKSUM, tag.startingSum);
     stroke.AddPropertyData(IS_HIGHLIGHTER, tag.isHighlighter);
     stroke.AddPropertyData(STROKE_TIMESTAMP_GUID, tag.timestamp);
     return tag;
 }
 public static double startingSum(this Stroke stroke, double startingSum)
 {
     stroke.AddPropertyData(STARTINGCHECKSUM, startingSum);
     return startingSum;
 }
 public static StrokeTag tag(this Stroke stroke, StrokeTag tag)
 {
     stroke.AddPropertyData(STROKE_TAG_GUID, tag.author);
     stroke.AddPropertyData(STROKE_PRIVACY_GUID, tag.privacy);
     stroke.AddPropertyData(IS_HIGHLIGHTER, tag.isHighlighter);
     return tag;
 }