cpdb-libs 2.0b6

In the sixth beta release for cpdb-libs 2.0.0 we have done more changes for sandboxed packaging, job data is streamed through domain sockets now and the frontend not being a D-Bus service any more. Also several crashers got fixed.

• Stream print data through a Unix domain socket
  To ease making a Snap from the CPDB backend for CUPS (and other CPDB backends in the future) we now transfer the print job data from the dialog to the backend via a Unix domain socket and not by dropping the data into a file (PR #30).
• Add newly appearing backends while the dialog is open
  CPDB Backends can get installed or removed at any time, also while a print dialog is open. Now a background thread is added to observe the come and go of backends and to update the printer list appropriately. New API functions are cpdbStartBackendListRefreshing() and cpdbStopBackendListRefreshing(), to start and stop this thread (PR #32).
• Added support for CPDB backends running permanently
  Do not only find backends as registered D-Bus services (*.service) files but also permanently running backends which are not necessarily registered D-Bus services
• Let the frontend not be a D-Bus service, only the backends
  To control hiding temporary or remote printers in the backend's printer list we have added methods to the D-Bus service provided by the backends now. Before, the frontends were also D-Bus services just to send signals to the backends for controling the filtering (PR #32).
• Convenience API functions to start/stop listing printers
  Added convenience API functions cpdbStartListingPrinters() and cpdbStopListingPrinters() to be called when opening and closing the print dialog, resp. (PR #32).
• Removed API functions cpdbGetAllJobs(), cpdbGetActiveJobsCount(), cpdbCancelJob(), and cpdbPrintFilePath() and the corresponding D-Bus methods (PR #30).
• Removed support for the FILE CPDB backend (PR #30).
• cpdbActivateBackends(): Fixed crash caused by wrong unreferencing
• cpdbConnectToDBus(): Use g_main_context_get_thread_default() for wait loop g_main_context_get_thread_default() always returns a valid context and never NULL. This way we avoid crashes.
• Fixed crash when Handling saved settings
  Let cpdbReadSettingsFromDisk() return an empty data structure instead of NULL when there are no saved settings. Also let cpdbIgnoreLastSavedSettings() always output and empty data structure.
• Removed the commands, get-all-jobs, get-active-jobs-count, and cancel-job from the cpdb-text-frontend utility (PR #30).
• cpdb-text-frontend: Removed unnecessary g_main_loop
  The g_main_loop is not actually needed, the main thread can just wait for the background thread using g_thread_join().
• cpdb-text-frontend: Shut down cleanly with stop command
  Instead of committing suicide with exit(0); we actually quit the main loop now.
• cpdb-text-frontend: Spawn command interpreter not before the start of the main loop, to assure that stop command quits main loop and we do not fall into an infinite loop.
• cpdb-text-frontend: acquire_translations_callback(): Only issue the success message and list the translation if the loading of the translations actually succeeded.