# layout_fit.ludic - aspect-ratio in layout: a width (fixed, a share, or fill) makes the height, a
# height the width, and neither the height from the content's width; object-fit in drawing: where a
# picture (or a native's content) of a natural size goes in the element's content box
function ly_ratio(n: UiNode, fixed_w: float, avail: float) -> void {
  if n.ex == null or n.ex.ratio <= 0.0 { return }
  let r = n.ex.ratio
  if n.h < 0.0 and n.h_pct <= 0.0 {
    var w = n.mw
    if fixed_w >= 0.0 { w = fixed_w } else if n.w == UI_FILL { w = avail - n.ml - n.mr }
    n.mw = w
    n.mh = w / r
  } else if fixed_w < 0.0 and n.w != UI_FILL and n.h >= 0.0 { n.mw = n.h * r }
}
# x, y, w, h: a `nat_w` x `nat_h` picture in the node's content box by its object-fit
export function ui_object_fit(n: UiNode, nat_w: float, nat_h: float) -> []float { return ui_object_fit_into(new []float, n, nat_w, nat_h) }
# ... into the caller's kept list (a draw every frame should: ui_object_fit makes one a call)
export function ui_object_fit_into(out: []float, n: UiNode, nat_w: float, nat_h: float) -> []float {
  let bx = n.x + n.pl + n.bl
  let by = n.y + n.pt + n.bt
  let bw = n.cw - ly_hin(n)
  let bh = n.ch - ly_vin(n)
  var k = 0
  if n.ex != null { k = n.ex.fit_obj }
  var w = bw
  var h = bh
  if k != 0 and nat_w > 0.0 and nat_h > 0.0 {
    var s = Math.min(bw / nat_w, bh / nat_h)
    if k == 2 { s = Math.max(bw / nat_w, bh / nat_h) }
    if k == 3 { s = 1.0 }
    if k == 4 { s = Math.min(s, 1.0) }
    w = nat_w * s
    h = nat_h * s
  }
  List.clear(out)
  ui_kept(out, bx + (bw - w) / 2.0)
  ui_kept(out, by + (bh - h) / 2.0)
  ui_kept(out, w)
  ui_kept(out, h)
  return out
}