Differ should delete unused files from differ_backup

[pintassilgo]

I noticed my differ_backup folder is full of files, but currently I don't have not even a single comparison open in session.

Differ should delete each file as soon as they are no longer needed, when they are removed from session.

[Alexey-T]

when they are removed from session.

we cannot detect this moment. but we can detect on_close - when any tab is closed. it is moment when user closes differ's pair-tab or individual tabs.

[pintassilgo]

Right, on_close is fine, that's what I meant when I said "session". Because when a tab is closed it's removed from session, even if session actually isn't updated instantly.

[Alexey-T]

ToDo for me.

[Alexey-T]

I failed to add it. I added deletion of temp-files, but it was activated too early - even when separate tabs are closed to make the Differ-tab. so some blocking of early deletion is needed. I am stuck

[pintassilgo]

In this case, maybe the cleanup can be done in other moment, like when the user attempts to close Cuda entirely. Differ would remove unused files from its backup folder.