V ecs is an Entity component System library for V that have a simplistic yet powerful design

What is ecs :

ECS is a programming pattern that is mostly used in games

• E: Entities which are in most cases just an id
• C: Component and thay are simple structs
• S: Systems and they are functions that use or change compenents

Usage :

V ecs have a very simple desing you basically have to create a struct and a function that use the data in that struct Here is an example

import gg
import gx
import mohamedlt.vecs as ecs

const (
    win_width  = 600
    win_height = 300
)

struct App {
mut:
    gg    &gg.Context
    image gg.Image
  // the world object is what makes everthing work 
    world ecs.World
}

// a Position Component 
struct Pos {
    ecs.Comp
mut:
    x f32
    y f32
}
// a Color Component
struct Color {
    ecs.Comp
    color gx.Color
}
// A Resource Can be anything from pictures to simple data 
struct Number{
    ecs.Resource
    val int
}

fn main() {
    mut app := &App{
        gg: 0
    }
  // add entity takes a list of the component you need in it 
    app.world.add_entity([Pos{x:0,y:20},Color{color:gx.gray}])
  // add system takes a function name and a list of compenets that must be in an entity to apply this system to 
    app.world.add_system(app.draw,[Pos{},Color{}])
  // same as above but just gives a mut entity 
    app.world.add_system_mut(frame,[Pos{},Color{}])
  // add resource to the world 
    app.world.add_resource(Number{val:2,name:'numb'})
    app.gg = gg.new_context(
        bg_color: gx.white
        width: win_width
        height: win_height
        create_window: true
        window_title: 'Rectangles'
        frame_fn: update
        user_data:app
    )
    app.gg.run()
}

fn update(mut app App){
  // world.step needs to be called every frame or whenever you want to update the world 
    app.world.step()
}
// any system needs to accept a mut entity or an unmut one and a ResourceManger 
fn(app &App) draw(e ecs.Entity,mut r ecs.ResourceManger){
    app.gg.begin()
  // Entity.get_comp return the component of that entity
    p := e.get_comp<Pos>()or {panic("")}
    c:= e.get_comp<Color>()or {panic("")}
  // ResourceManger.get_resource takes a resource name and returns it 
    speed := r.get_resource<Number>('numb')or {panic("")}
    println(speed.val)
    app.gg.draw_rect_filled(p.x,p.y,20,20,c.color)

    app.gg.end()
}
// this is a system that takes a mut entity and moves it 
fn  frame(mut  e ecs.Entity,mut r ecs.ResourceManger){
    mut pos := e.get_comp<Pos>() or {panic('')}
    pos.x++
}

Notes:

• A compenet must embed ecs.Comp or have a active field
• A Resource must embed ecs.Resource or have a name field