This is a battery-saving measure. Whether a sensor should be suspended
is determined in the same way as whether key events and motion events
should be handled by the OS rather than consumed by Dolphin.
When Android presents an input event to an app, it wants the app to
return true or false depending on whether the app handled the event or
not. If the event wasn't handled by the app, it will be passed on to
the system, which may decide to take an action depending on what kind
of input event it is. For instance, if a B button press is passed on to
the system, it will be turned into a Back press. But if an R1 press is
passed on to the system, nothing in particular happens.
It's important that we get this return value right in Dolphin. For
instance, the user generally wouldn't want a B button press to open
the EmulationActivity menu, so B button presses usually shouldn't be
passed on to the system - but volume button presses usually should be
passed on to the system, since it would be hard to adjust the volume
otherwise. What ButtonManager did was to pass on input events that are
for a button which the user has not mapped, which I think makes sense.
But exactly how to implement that is more complicated in the new input
backend than in ButtonManager, because now we have a separation between
the input backend and the code that keeps track of the user's mappings.
What I'm going with in this commit is to treat an input as mapped if
it has been polled recently. In part I chose this because it seemed
like a simple way of implementing it that wouldn't cause too many
layering violations, but it also has two useful side effects:
1. If a controller is not being polled (e.g. GameCube controllers in
Wii games that don't use them), its mappings will not be considered.
2. Once sensor input is implemented in the Android input backend,
we will be able to use this "polled recently" tracking to power down
the sensors at times when the game is using a Wii Remote reporting
mode that doesn't include motion data. (Assuming that the sensor
inputs only are mapped to Wii Remote motion controls, that is.)
Android doesn't let us poll inputs whenever we want. Instead, we
listen to input events (activities will have to forward them to the
input backend), and store the received values in atomic variables
in the Input classes. This is similar in concept to how ButtonManager
worked, but without its homegrown second input mapping system.
ButtonManager is very different from how a normal input backend works,
and is making it hard for us to improve controller support on Android.
The following commits will add a new input backend in its place.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Android doesn't report values for the inputs generated by FullAnalogInput so
there isn't a reason to add them as such. This also avoids a bug(for android)
where if there are three inputs(say 12, 11, and 121), and you generate a FullAnalogInput
with 12/11 then it will create another input with the name 121 which can cause conficts
with the real 121 input. This is probably not an issue on PC since most Axis inputs
are named and not numbered.
The SDL backend crashes when you close a joystick after SDL_Quit has
been called. Some backends don't need to be shutdown and
re-initialized everytime, we can just ask to enumerate devices again.
This makes the device ID assigning code common to all backends, by
moving it to AddDevice() instead of copy-pasting or replicating
the logic in the backends.
Also, to prepare for hotplugging, instead of relying on a name usage
count, the new ID assigning system always starts from ID 0 and tries
to assign the first ID that is not used.
Small cleanup by using std::shared_ptr and getting rid of
ciface.Devices() which just returned the m_devices (which defeats the
point of making m_devices protected).
Incidentally, this should make the code safer when we have
different threads accessing devices in the future (for hotplug?).
A lot of code use Device references directly so there is
no easy way to remove FindDevice() and make those unique_ptrs.
Previously, the devices vector would be passed to all backends. They
would then manually push_back to it to add new devices. This was fine
but caused issues when trying to add synchronisation.
Instead, backends now call AddDevice() to fill m_devices so that it is
not accessible from the outside.
