extends Node2D
# Converted from https://processing.org/examples/functions.html
#
# Set the window size to 640 by 360 pixels in
# Godot > menu Project > Project Settings... > tab General > 
# Display > Window > Width: 640, Height: 360
#
# Set the background to black color in
# Godot > menu Project > Project Settings... > tab General > 
# Rendering > Environment > Define Clear Color

# screen size - will be updated later on resize of the window
var width = 640
var height = 360

# Called when the node enters the scene tree for the first time.
func _ready():
	# Register the size_changed event
	get_tree().get_root().connect("size_changed", self, "on_size_changed")
	update_width_and_height()
	
# Event called on window size change
func on_size_changed():
	update_width_and_height()

# Read screen size and store it in the global variables
func update_width_and_height():
	var size = get_viewport_rect().size
	width = size.x
	height = size.y

# Called automatically only once after enter scene tree. 
# If re-drawing is required, call update() on this node.
func _draw():
	drawTarget(width*0.25, height*0.4, 200, 4)
	drawTarget(width*0.5, height*0.5, 300, 10)
	drawTarget(width*0.75, height*0.3, 120, 6)

# Draw the target object
func drawTarget(xloc,  yloc,  size,  num):
	var grayvalues = 255/num
	var steps = size/num
	for i in range(0, num):
		var c = i * grayvalues
		var fillColor = color256(c, c, c)
		#ellipse(xloc, yloc, size - i*steps, size - i*steps)
		draw_circle(
			Vector2(xloc, yloc), 
			(size - i*steps)/2, 
			fillColor)

# Helper to draw a circle
func draw_circle_arc(center, radius, angle_from, angle_to, color):
	var nb_points = 64
	var points_arc = PoolVector2Array()
	
	for i in range(nb_points + 1):
		var angle_point = deg2rad(angle_from + i * (angle_to-angle_from) / nb_points - 90)
		points_arc.push_back(center + Vector2(cos(angle_point), sin(angle_point)) * radius)
	
	for index_point in range(nb_points):
		draw_line(points_arc[index_point], points_arc[index_point + 1], color)

# Helper to convert rgb values 0..255 to 0..1 range
func color256(r,g,b):
	return Color(r/255.0, g/255.0, b/255.0)