launchpad - What package to file general (usability) bug against?

I am experiencing a bug where on first login to an Ubuntu/Unity session (12.04), my mouse buttons are not inverted (left-handed). The configuration does correctly list them as inverted, but they don't behave that way. If I log out and login again, they behave correctly, as per the configuration. It worked correctly for the longest time and only recently started misbehaving.

Now my question is: how should one report such a bug? I have no idea what package or process causes the problem. In fact, there may be multiple packages involved. I have a Launchpad account and have reported bugs, or added information to bugs, in the past, so I'm familiar with the process. I just can't figure out how to report this without taking a guess at the responsible process to pass to ubuntu-bug.

While it is possible to report bugs without specifying a package (as you've discovered), bugs reported that way virtually never have any progress made on them until a package gets specified.

So it's best to report a bug against a specific package whenever possible. You shouldn't randomly guess, but it is OK to report a bug against the wrong package if you had reason to believe it was the most likely package.

If you had to report this bug with no further information, I'd recommend reporting it against gnome-settings-daemon (remember, Unity is a shell for GNOME, a Unity desktop is GNOME). Probably that is what's preventing the setting from being applied correctly some of the time. This is (most likely) the package that should be applying the setting at login, and is not doing so properly.

If you happened to have KDE installed too, and it happened there as well (even when no GNOME login had taken place since reboot), then xserver-xorg-input-mouse, which provides mouse input functionality to the GUI, might potentially make more sense.

But gnome-settings-daemon is your best bet, right now.

It's best to start a bug report with ubuntu-bug but if you already filed the bug on Launchpad, you don't have to report it again (unless asked to do so). Instead, specify gnome-settings-daemon as the package. Once the bug report is targeted against that, run

apport-collect BugNumber

where BugNumber is replaced with the bug number on Launchpad. This will automatically collect and attach (at least most of) the technical information that would have been attached had you started the bug reporting process by running ubuntu-bug.

^{If you wish, feel free to subscribe me to the bug. (I'm not a triager or developer though; I might not end up helping any.)}