Doesn't find games that provide .desktop files in Game category

Migrated from https://bugzilla.gnome.org/show_bug.cgi?id=781338

Niklas Rosenqvist niklas.s.rosenqvist@gmail.com:

I expected it to be able to list the games that are providing a .desktop file. A normal user probably wouldn't have any idea where games are installed and much less how to configure the app to search for them. It would be helpful for the average user to make the app able to list all games in the Game cateogry since there really is no standard to where games are installed, some are in /opt, others are packaged properly and steam games are often found in the home directory.