If markContentsDirty is invoked on a document while an edit block is in progress (I ran into this scenario by calling rehighlight() on a QSyntaxHighligher), any slots connected to the document's contentsChange signal are not informed about changes that happened prior to the call.

See the attached reproduction project. It adds 3 characters, forces a re-highlight, and then adds another 3 characters.

If commenting out the highligher.rehighlightBlock call, we get:

Added 6 characters from 0 

If not, we get:

Added 3 characters from 3 

Which is wrong. I'd expect the slot to be invoked with all the changes, though perhaps more than once.