Detect currently active input device

[TimJentzsch]

What problem does this solve?

As a user, I want to have UI overlays that fit the input device I'm currently using (e.g. either shortcut keys when I'm using my mouse and keyboards, or gamepad glyphs if I'm using a gamepad).

As a developer, I want an easy way to detect which device is currently active, so that I can adapt my UI accordingly.

What solution would you like?

I think the easiest way would be to provide a Resource which contains an enum indicating the currently active device. This enum should be updated by the plugin automatically.

Ideally, for controllers it would even identify the device type, e.g. if it's an Xbox of PS controller, so that the glyphs can be shown accordingly. But I'm not sure if that's possible.

[Optional] How could this be implemented?

• Init the resource with some default value and let the dev provide a default if they want.
• Update the resource in a system which listens to input events:
  • A key/button press immediately changes the resource to this device.
  • Mouse or joystick movement only changes the resource if a threshold is exceeded (because this can happen accidentally).

[Optional] What alternatives have you considered?

This could also be handled manually by the developer. I think a built in solution that works well would be nice though. This makes it easier to add proper gamepad support.

Related work

• The Steamworks documentation has a guideline that on-screen icons and the cursor should match the active input device.
• The documentation also links this article which lays down more rules for game input and ideas on how to implement them. It also covers the detection of the active input device.

  • I call this the Timestamp Input Engine. The main idea is that you store 2 timestamps that indicate the time when the last input event was received for both gamepad and keyboard/mouse. Every time you detect a valid input event, you update the appropriate timestamp variable with the current game time. Make sure to use elapsed game time, not delta-time or a time that might get paused or dilated.

  • Now that you have timestamps indicating the last gamepad and keyboard events, the actual input detection is as easy as seeing which timestamp is greater.

[alice-i-cecile]

I'm on board with this as a feature :) Ideally it should be toggleable via plugin settings.

Ideally, for controllers it would even identify the device type, e.g. if it's an Xbox of PS controller, so that the glyphs can be shown accordingly. But I'm not sure if that's possible.

This is likely to require examining information provided by glam. I'm not sure if they currently expose this information; it may require a PR upstream.

Definitely split this part out into future work :)

[TimJentzsch]

Ideally it should be toggleable via plugin settings.

Why is this necessary? It would already be optional to use the provided resource. Or is it to save resources by disabling the updating system?

[alice-i-cecile]

The latter :) Most desktop apps don't care about this functionality, so it's good to split it out in some way.

Perhaps an entirely seperate plugin?