I am not sure this is a potential bug or this is an designed behaviour.
Based on the documentation here: https://api.onlyoffice.com/editors/config/events
The steps to reproduce the issue:
Browsers: Chrome 57.0.2987.98 or Firefox 47.0
OS: Ubuntu 15.10
2. Wrap this event object in to config object as member of events property based on the documentation https://api.onlyoffice.com/editors/config/editor.
3. Open a document in editor, check the callback function is invoked when there is any change made and saved.
4. Leave the editor open, open another editor window by using a different user, the callback function will never be invoked any more in both of editor window when changes are made
What I expected is in fast co-edit mode, no matter how many users are editing the specific document, this event will still be triggered so that the callback function bind to onDocumentStateChange event can be invoked correctly for each user rather than having to switch co-edit mode to strict.
Please check this issue, thank you.
If this is designed behaviour, I request to change it as we've already have onCollaborativeChanges event, which makes more sense to use this event when people want to capture document change when multiple users are editing the same document and I'm ok with this event to work only in strict mode, but I reckon onDocumentStateChange should reflect individual's no matter what the current co-edit mode is.