Add a way to use the virtual trackpads to control the mouse

[atabuchiy]

The virtual trackpads are nice for those few games that requieres them, but are almost useless otherwise.

It would be nice if there is a way to use them as a regular trackpad (control mouse) for other games (and desktop) that requiere more precise control than a touchscreen or joystick could provide.

Also, it would be nice it there is a way to enable it while holding a key instead of toggling it on and off.