class_name ViewUtils
extends RefCounted

# Computes the exact world-space rect currently visible on screen by
# transforming the viewport's real screen corners through the actual canvas
# transform, instead of approximating with viewport_size * camera.zoom
# (which assumes a simple centered mapping - stretch/aspect="expand" doesn't
# necessarily expand symmetrically around center, which was making that
# approximation under/over-shoot on one side and cull content that was
# actually on screen).
static func get_visible_world_rect(node: Node) -> Rect2:
	var canvas_transform: Transform2D = node.get_viewport().get_canvas_transform()
	var inverse: Transform2D = canvas_transform.affine_inverse()
	var size: Vector2 = node.get_viewport_rect().size

	var corners: Array = [
		inverse * Vector2(0, 0),
		inverse * Vector2(size.x, 0),
		inverse * Vector2(0, size.y),
		inverse * Vector2(size.x, size.y),
	]

	var min_pt: Vector2 = corners[0]
	var max_pt: Vector2 = corners[0]
	for c in corners:
		min_pt.x = min(min_pt.x, c.x)
		min_pt.y = min(min_pt.y, c.y)
		max_pt.x = max(max_pt.x, c.x)
		max_pt.y = max(max_pt.y, c.y)

	return Rect2(min_pt, max_pt - min_pt)