Questions on porting this to GLFW

[sro5h]

I am trying to port this to GLFW and have a few question regarding the implementation. When defining the observer for Sdl2DestroyWindow the Sdl2Window parameter is marked with [in] and () at the end.

1. Shouldn't that be [inout] as SDL_DestroyWindow changes the data referenced by the Sdl2Window component?
2. As far as i understand the parantheses at the end they define an empty predicate that always evaluates to true. So is the expression equivalent to [in] ?flecs.systems.sdl2.window.Window?
3. If so, why is the Sdl2Window parameter for the SdlDestroyWindow observer marked as optional?

Furthermore i have the problem that GLFW uses callbacks to pass on input events. I tried to pass the ecs_world_t to the callback as a context parameter and used ecs_singleton_get_mut(EcsInput). But then i hit an assert telling me that the world is in readonly mode. How can i modify components from callbacks?