Comment 10 for bug 899624

Extending UCA to other URI schemes is not as straight-forward as it seems.

Most custom actions do not support URIs yet. %u and %U are supported but not documented. This information needs to be added to the UCA edit dialog.

It is unclear whether we should expand %d, %D, %f and %F to URIs. Changing the behavior of these placeholders might break existing custom actions, so I think we have to introduce URI alternatives for %d and %D at least. This is even more important as some URIs and URI schemes cannot be converted to local paths, even if gvfs-fuse is available. So e.g. for some trash:// smb:// URIs (generally all URIs for which g_file_get_path() returns NULL), only custom actions that support URI parameters should be displayed.