Document which button types are pressable

[stepancheg]

No description provided.

[rlidwka]

KeyCode and ScanCode aren't buttons. "Input types" perhaps?

I suggest to do the same exact changes to Axis<T> struct (which has GamepadButton and GamepadAxis, and that's not documented anywhere either).

It is a bit unfortunate that Input is not self-documenting, ideally we'd have Input<T: InputType> instead of Input<T: Copy + Eq + And + Stuff>, and users could've just looked up which types implement InputType trait. But that's probably gonna break something, so better not.

[stepancheg]

ideally we'd have Input<T: InputType>

I wanted to do it, it resulted in strange compilation errors, I suspect because of this dependency cycle:

bevy/crates/bevy_input/Cargo.toml

Lines 29 to 30 in 24c6a7d

	[dev-dependencies]
	bevy = { path = "../../", version = "0.12.0" }

[stepancheg]

I suggest to do the same exact changes to Axis struct

Why stop at Axis why not document anything else? There's a lot of things can be documented in bevy.

I don't use Axis and after quick look I don't understand what it does, so I didn't document it. Also PRs are open for everyone, you know.

[Nilirad]

The generalization from "button types" to "input types" makes it less confusing, I like it.

I agree with @rlidwka that Input<T> and Axis<T> should be more self-documenting, so we don't have to manually maintain a list, with the added benefit of not allowing types that aren't meant to go there but they happen to have the right traits. But that's for another PR since it's more controversial and breaking.

[TrialDragon]

This PR's branch should merge or rebase main since relevant changes, and conflicts, have occurred.

[TrialDragon]

Suggested change

	/// ## Input types
	///
	/// This crate provides support for the following parameters of `Input`:
	///
	/// * [`KeyCode`](crate::KeyCode) and [`ScanCode`](crate::ScanCode) for keyboard input
	/// ## ButtonInput types
	///
	/// This crate provides support for the following parameters of `ButtonInput`:
	///
	/// * [`KeyCode`](crate::KeyCode) for keyboard input

Input has since been renamed ButtonInput and ScanCode removed with KeyCode taking it's place as the physical key. (I do not remember if Key, the present logical key, is relevant to ButtonInput at all).