Initializes the extension. This must be called before doing anything else.
flags are bit flags (added together via |) that indicate types of devices that the extension will poll:
- raw_input_watch_hid_mice: HID devices that claim to be able to function as mice.
- raw_input_watch_system_mouse: Prepends a virtual device (taking index 0) that will take input from any other devices - like the default system cursor does.
- raw_input_watch_rdp_mice: Remote Desktop Protocol mice.
- raw_input_watch_hid_keyboards: HID devices that claim to be keyboards.
If not specified, default value is raw_input_watch_hid_mice|raw_input_watch_hid_keyboards.
: By which I mean - having virtual devices (which the user cannot control) isn't uncommon, so you should ideally require input/confirmation before assuming that they are in use.