This question has been asked a couple of times also on AskUbuntu so I thought it is worth a blog post to elaborate on why in certain circumstances Diodon doesn’t save anything to the clipboard history and what you can do about it.
Since version 1.1.0 the way how Diodon stores its clipboard storage has changed – it used to be that the history was simply stored in the storage.xml file located in ~/.local/share/diodon/. This was fairly simple but had the limitation that the clipboard history was limited to a certain number of entries. If we wanted to increase this number but still using the single xml file Diodon would consume way too much memory and would have become too slow as well. To overcome this limitation have we moved away from this xml file and integrated a library called Zeitgeist.
Quick quote what Zeitgeist actually is:
Zeitgeist is a service which logs the users’ activities and events, anywhere from files opened to websites visited and conversations had.
As Diodon pretty much records users’ copy events is using Zeitgeist service a really good match. Besides recording Zeitgeist also provides a simple way to search certain activities and managing history which gives Diodon beside an infinitive clipboard history many more opportunities read more about it here.
But let’s get back to our initial question on why Diodon does not save anything to the clipboard history. For this we have to know that Zeitgeist has a privacy feature so it is possible to disable recording of any users’ events. This option is to be found in your “System Settings” -> “Security & Privacy” -> “Files & Applications” where it says “Record file and application usage”. When you turn this option off no users’ events will be recorded including copy events by Diodon. This means you can still access previous copy events recorded before disabling this option but no new items will be added. You properly ask yourself now how you can simply allow Diodon to save copy events but disable other applications from recording anything?
This is possible but at this stage not as apparent as it could be. In the same Security & Privacy dialog from above there is the possibility to enable recording but only including certain activities. Unfortunately is there no entry to simply include Clipboard. This is something we would really like to see in the future and are working on it – you can follow progress in this bug report. For now as a workaround to still allow Diodon to save copy events is to at least allow activity “Documents” to be recorded.
When this option is set you should be good to go and Diodon should start adding clipboard items to the history again.