Saving User Preferences

There are now a few areas of the launcher to which the user can apply new states, but these are not presently persistent across multiple sessions.

To improve the user experience things like the server browser filter options (which games you've unselected) should be saved to a user preferences file. This should be a common interface which multiple areas of code can share and re-use.

This will feed into the player count notifications service and also open the door to features such as "favourite servers"