Add button to clear queue

[jeremypw]

Partially addresses #40 in conjunction with #161

At present the button purges all jobs without confirmation. Design input needed as to whether confirmation needed or whether should only clear completed jobs etc.

Should the Clear button be separated from the Print Test Page button?

[jeremypw]

[danirabbit]

Yeah we should probably have a confirmation dialog here since this is a potential accidental data loss situation

We should probably place the button in an actionbar in the list frame so that it's more clearly associated with the list and also so it doesn't show when we switch pages to page setup, etc

[jeremypw]

@danrabbit I think there is a separate queue for each printer destination (I'll check) so in that case we need to decide whether the button clears the queue for the printer page it is on - or all queues. This will affect its appropriate location.

[jeremypw]

Yes, each printer page has its own queue and at the moment the button on that page clears only the queue for that printer. So it seems reasonable for the button to be close to the queue it is going to clear. The action will be made clearer by having a confirmation dialog.

If desired a button "Clear all Printer Queues" could be added to the Printer List action bar (when there are > 1 printer)

[jeremypw]

I have added a confirmation dialog now. I have also filtered the job list so that only pending and completed jobs are listed - this is so the "Clear" button removes all visible jobs.

[jeremypw]

Note that at present, the CUPS server keeps a list of cancelled jobs so clearing the queue is more of practical use than to completely protect privacy.

[jeremypw]

It is noted that there is a commandline function cancel -ax that purges all jobs and removes the associated data but this function does not appear to be exposed by "org.opensuse.CupsPkHelper.Mechanism" or cups.vapi?

[jeremypw]

It is also noted that the job status does not update in the list (i.e. a job appears to be pending even when it is completed unless you restart the switchboard) - I'll fix that in a separate PR if I can.

[danirabbit]

Sorry for taking a while to review this! I just realized today I could test the queue by creating a print-to-file printer. Can you resolve conflicts here?

[jeremypw]

@danrabbit Conflicts resolved.

[danirabbit]

It looks like this no longer shows pending jobs. So for example I'm unable to resume a job that was paused

Screenshot of the suggested changes to dialog:

[jeremypw]

@danrabbit Thanks for the review. I have committed your suggestions. I cannot reproduce your issue with pause/resume though. I can pauses and resume a pending job (creating by printing a test page to an unplugged printer) without problem. I can also clear such jobs.

I did notice another issue with the action revealer which hides when a second job is started after a pending one, but that is present in master. I'll try and fix it in another PR.

[danirabbit]

I found the source of the issue and left an inline comment. To reproduce, start and then pause a job. Close and reopen System Settings. You'll notice the paused job is gone.

[danirabbit]

This can be removed as well right?

Suggested change

	public bool canceled_or_aborted {
	get {
	return (state == CUPS.IPP.JobState.CANCELED) ||
	(state == CUPS.IPP.JobState.ABORTED);
	}
	}

[jeremypw]

Yup. Done

[jeremypw]

I have now removed that filter. I still think that maybe cancelled and aborted jobs should be listed separately from successfully completed jobs but that is outside the scope of this PR.

[danirabbit]

Nice work! 🎉