Handling input from an ECS input system into actions in another system/actions on a entity?

Question

Some background on my engine, each system stores a reference to an entity which has the relevant components for that system. For example movement system has only entities which possess position components, render system takes positions and textures etc.

I'm working on an Entity-Component-System Game Engine for a project and I've hit a bit of a brick-wall in regards to how I'm going to handle input for the entities. I'm unsure of how I would translate say a "W" press input into the movement of a single entity(the player)? I don't want to move the entity inside the input system. I'm unsure of how to go about taking input and getting it to result in a response.

This is my first question, if there's anyway I can improve it or if theres any additional information needed I'd be happy to oblige.

Answer 1

This is just a short answer, since many details of your engine are unknown to me.

You need to remember that your InputSystemshould not cause the movement directly, as it may be context dependent when you press 'W'. Are you in a menu and your button selection should move up, character should move forward and in a vehicle accelerate. Additionally, your InputSystem does not know about the surrounding. Is a wall infront of the player, is the player in the air etc.
What it should do is change the acceleration of the player or the object. It should write this in a component that both the InputSystemand the MovementSystemcan access, e. G. the MovementComponent.

The MovementSystemin this case is more like a PhysicsSystem. It reads in the MovementComponent that the entity wants to move in the 'W'-direction. It checks, if that is possible. Is there a wall? Is the player on the ground (or ice, conveyer belt etc.) and then calculates the new position. This is then written in the PositionComponent.

Of course the context of your input can be checked in another sytem than your InputSystem, like the system that sort of is the game, some GameruleSystem. In this case the InputSystem writes the command in the MovementComponent, GameruleSystemreads this and reads the context, then writes in the PhysicsComponentwhat should happen. Moving forward, moving upwards, jumping. This is dependent on the game type.