Comment 12 for bug 216939

Further: the problem will not occur if one is running gnome-screensaver. This is probably why the issue isn't being reproduced by everyone.

lib/totem-scrsaver.c looks for org.gnome.ScreenSaver on DBUS. If it finds gnome-screensaver running, it sends an Inhibit message and stops there. If it doesn't, it assumes you're running some other brand of screensaver, and falls back to sending XTestFakeKeyEvents of the Alt key every 30 seconds. This behaviour has undesirable side effects as detailed here.

[And if, for example, you're not running *any* screensaver (because, for example, you happen to find them a frivolous waste of time), it's doing this for no purpose.]

Possible fix (1): change the ticky to a drop down with options 'Disable screensaver for audio and video'/'Disable screensaver for audio only'/'Never disable screensaver'

Possible fix (2): assume Ubuntu users will be using gnome-screensaver if anything, and remove the fake-key fallback (or compile WITHOUT_XTEST)

Possible fix (3): find a different X11 method for subverting the screensaver. A different key? Ctrl would seem to have fewer side-effects, but still is far from ideal. Is there eg. another obscure shifting key most keyboards don't have, or something like that?

Possible fix (4): invent a freedesktop standard for inhibiting screensavers, and use that exclusively.