Idea: export variable as input action

[theraot]

I have a set of scripts where I configure an input action (the name of an action from the input map). While I've been able to use _get_property_list to provide a list of options, it is common enough - at least for me - that I believe it could use editor help.

Example of what I've used:

@tool
extends Resource

var action_name: StringName = &""

func _get_property_list() -> Array[Dictionary]:
	var list_of_actions:String = ""
	InputMap.load_from_project_settings()
	for action in InputMap.get_actions():
		if not list_of_actions.is_empty():
			list_of_actions += ","

		list_of_actions += str(action)

	return [
		{
			"name": "action_name",
			"type": TYPE_STRING_NAME,
			"hint": PROPERTY_HINT_ENUM_SUGGESTION,
			"hint_string": list_of_actions,
			"usage": PROPERTY_USAGE_SCRIPT_VARIABLE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_STORAGE
		}
	]

So, I would want to write:

@export_action var action_name: StringName = &""

And while we are at it, I would rather have the custom actions at the top, currently I get the build-in ones at the top.

[Calinou]

This would also be useful for TouchScreenButton's action property, although it should allow entering custom names to support actions that are programmatically created at runtime.

[baznzab]

I've spent some time implementing this feature via custom plugin and have some thoughts:

1. Using InputMap.load_from_project_settings() inside editor script is insecure because it removes all editor related bindings and breaks its behavior. It's better to get actions directly from EditorSettings, similar to how it's done in InputMap::load_from_project_settings().
2. Using enum-like gui for such properties isn't the best. QuickLoad-like gui would suit much better here I think. EditorQuickOpen class could be reused. I tried to mimic it in my plugin, you can see it on the video attachment, but it lacks some qol features like search for example. https://github.com/godotengine/godot-proposals/assets/67281067/93ccf5ba-0426-4508-b78c-c967e4dfbce3
3. Although it is possible to achieve such behavior with custom plugin it isn't the best solution cause it requires a wrapper around input action's StringName.

Here is my plugin implemented in gdscript.
https://github.com/baznzab/input_action_reference
Posting it just for the reference and to represent what i mentioned above.