use custom draw function from autoload

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:information_source: Attention Topic was automatically imported from the old Question2Answer platform.
:bust_in_silhouette: Asked By newbie09

I have autoloaded Engine.tscn as engine

Engine.gd attached to Engine.tscn

extends Node2D

func polygon(center:Vector2, points, radius, rotation, outline:bool, thick, color:Color, alpha):
	
	print_debug("drawing polygon")
	
	var c : PoolColorArray
	var p : PoolVector2Array
	
	var pp : PoolVector2Array
	var cc : PoolColorArray
	
	var x
	var y
	var ang = 360/points
	
	color.a = alpha
	
	if not outline:
		thick = radius
	
	for i in range(points+1):
		
		x = cos(deg2rad(ang*(i%points)+rotation))*radius + center.x
		y = sin(deg2rad(ang*(i%points)+rotation))*radius + center.y
		
		c.append(color)
		p.append(Vector2(x,y))
		
		if i > 0:
			draw_primitive(p, c, p, null, 1, null)
			c.remove(0)
			p.remove(0)
		
		x = cos(deg2rad(ang*(i%points)+rotation))*(radius-thick) + center.x
		y = sin(deg2rad(ang*(i%points)+rotation))*(radius-thick) + center.y
		
		c.append(color)
		p.append(Vector2(x,y))
		
		if i > 0:
			draw_primitive(p, c, p, null, 1, null)
			c.remove(0)
			p.remove(0)

Main.gd attached to Main.tscn

extends Node2D

var runtime = 0

func _ready():
	pass

func _process(delta):
	runtime += delta
	
	update()

func _draw():
	engine.polygon(
		OS.get_real_window_size()/2,
		3, 50, runtime*100, true, 25, Color.cyan, 1)

but nothing draw.

ERROR: draw_primitive: Drawing is only allowed inside NOTIFICATION_DRAW, _draw() function or ‘draw’ signal.
At: scene/2d/canvas_item.cpp:866.

I’m totally new to Godot and can’t really find a solution
is there anyway I can create a draw function that can call globally cause this polygon is gonna be use a lot in my project