Setting data from a QByteArray and disabling overwrite mode, it can be useful to query the current size of the data, to track the state or prepare and check some other things before querying the current data edited.
Currently the purpose only seems possible by getting the full current data by calling data() and then querying the size on that. Though this seems some expensive operation, by a quick look at Chunks::data() Would be more nice to be able to query the widget just for this info, which hopefully can be easily get from some data.