Customize default systems for all scenes

[mattjennings]

Context

It would be helpful to configure the default systems to be used for all scenes. This spares having to make a base scene class with the system added if I want to make sure it's always used.

Proposal

// proposal 1
new ex.Engine({
   world: {
       systems: [...], // adds to current systems
       removeDefaultSystems: true/false // removes default if true
    }
})

// proposal 2
new ex.Engine({
   world: {
       systems: [...], // overrides systems, must add back ex.MotionSystem etc
    }
})

[eonarheim]

I'm into this, I'm leaning towards #1 because re-adding systems seems really rough... but on the other hand that's only once?

[mattjennings]

I agree, i feel like you'd need to expose the default systems somewhere to they can be spread in. Here's 2 more ideas:

// proposal 3
new ex.Engine({
   world: {
       systems: [...ex.DefaultSystems, MySystem],
    }
})

// proposal 4
new ex.Engine({
   world:  {
       setup(world) {
           world.systemManager.addSystem(MySystem)
       }
   }
})

[Autsider666]

I like the removeDefaultSystems option from proposal 1 a lot, because it currently takes a bit of work to get a scene without the default systems preloaded.

Using a callback (proposal 4) feels like the "best" method to me, because it prevents the reuse of system instances between scenes (causing initialize to be called more than once).

What about adding initializeWorld: (world:World)=>void to the scene constructor that falls back to a default function that adds the systems currently added in the constructor.
This default function could be overwritten if needed using something like proposal 4

[github-actions]

This issue hasn't had any recent activity lately and is being marked as stale automatically.