Godot: Animation only plays when screen is being resized - animation

Question

My game starts with a splash screen of a starfield flying towards the player. The first frame draws fine, but subsequent frames only draw while the window is actively being resized.
I just migrated from Godot 3.5.1 to 4.0.beta5 and had to do a bit of code refactoring just to get it semi-functional.
extends Node2D
const WIDTH = 1920
const HEIGHT = 1080
const STAR_COUNT = 400
const PLANET_COUNT = 5
var splash_stars = []
var theta
var offsetz
var x
var dx
var y
var dy
var radius
var alpha
var planet_scale
var color
var rng
func _ready():
rng = RandomNumberGenerator.new()
rng.randomize()
# initialize the stars animation
var Star = load("res://stars.gd")
for _i in range(STAR_COUNT):
theta = rng.randi()%360
offsetz = rng.randi()%(HEIGHT -1) + 1
x = offsetz * cos(theta) + WIDTH / 2.0
dx = 2.5 * cos(theta)
y = offsetz * sin(theta) + HEIGHT / 2.0
dy = 2.5 * sin(theta)
radius = 100 / offsetz
alpha = 0
var star = Star.new(theta, offsetz, x, dx, y, dy, radius, alpha)
splash_stars.append(star)
func update_star_coords():
for splash_star in splash_stars:
splash_star._dx = splash_star._dx * 1.005
splash_star._dy = splash_star._dy * 1.005
splash_star._x += splash_star._dx
splash_star._y += splash_star._dy
splash_star._radius += .025
splash_star._alpha += .005
if 0 > splash_star._x or splash_star._x > WIDTH or 0 > splash_star._y or splash_star._y > HEIGHT or splash_star._radius > 8:
splash_star._theta = rng.randi()%360
splash_star._theta = deg_to_rad(splash_star._theta)
splash_star._offset = rng.randi()%(HEIGHT - 1) + 1
splash_star._x = splash_star._offset * cos(splash_star._theta) + WIDTH / 2.0
splash_star._dx = 2.5 * cos(splash_star._theta)
splash_star._y = splash_star._offset * sin(splash_star._theta) + HEIGHT / 2.0
splash_star._dy = 2.5 * sin(splash_star._theta)
splash_star._radius = 100 / splash_star._offset
if splash_star._radius < 1:
splash_star._radius = 1
splash_star._alpha = 0
func _draw():
for splash_star in splash_stars:
var center = Vector2(splash_star._x, splash_star._y)
color = Color(1, 1, 0, splash_star._alpha)
draw_circle(center, splash_star._radius, color)
func _process(delta):
update_star_coords()
And the 'stars' class:
extends Node2D
var _theta
var _offset
var _x
var _dx
var _y
var _dy
var _radius
var _alpha
func _init(theta,offset,x,dx,y,dy,radius,alpha):
self._theta = theta
self._offset = offset
self._x = x
self._dx = dx
self._y = y
self._dy = dy
self._radius = radius
self._alpha = alpha

Answer 1

You need to call update (queue_redraw in Godot 4.0) to tell Godot that it needs to call _draw again.
You can read about it in Custom drawing in 2D.