Description of problem:
Unfortunately while working on this issue:
I have realised that we don't get to pass through some optional parameters when using PolicyKit.
The available optional parameters for CUPS-Get-Devices are:
1. limit, an integer, specifying the maximum number of devices to return
2. include-schemes, a list of strings specifying the inclusion list for returned device URI schemes
3. exclude-schemes, a list of strings specifying the exclusion list for returned device URI schemes
The include-schemes and exclude-schemes parameters are mutually exclusive.
There are currently no others.
Version-Release number of selected component (if applicable):
I don't think it's possible to have optional parameters with D-Bus so we need some way to signal whether the parameters should be used or not -- perhaps just '0' for no limit and empty list for the other two. In other words, include-schemes would only be used if non-empty, otherwise exclude-schemes.
This is an API break so will need either a new interface name (can we do that?) or new policy mechanism method name.
...and of course I'm wrong, the D-Bus API supports this already (yay!), just that system-config-printer's cupspk doesn't yet.