# attr_inset.ludic - top, right, bottom and left as lengths, percentages or calc() of both: the
# percentage is kept apart and taken of the containing block's width (left, right) or height (top,
# bottom) when the element is placed
function el_inset(ui_st: mut UiState, n: UiNode, side: int, v: Val) -> float {
  let s = vl_text_u(ui_st, v)
  var pct = 0.0
  var px = UI_AUTO
  if s != "auto" {
    if ca_is(s) {
      px = 0.0
      if ca_eval(ui_st, s) {
        pct = ui_st.ca_pct
        px = ui_st.ca_px
      }
    } else if len(s) > 1 and s[len(s) - 1] == 37 {
      pct = el_num(s)
      px = 0.0
    } else { px = el_len(ui_st, v) }
  }
  if pct != 0.0 or n.ex != null {
    let x = nx(n)
    if side == 0 { x.ip_t = pct }
    if side == 1 { x.ip_r = pct }
    if side == 2 { x.ip_b = pct }
    if side == 3 { x.ip_l = pct }
  }
  return px
}
# an inset in px against a containing block `base` wide (or high), or UI_AUTO
function ly_ins(c: UiNode, side: int, base: float) -> float {
  var v = c.top
  if side == 1 { v = c.right }
  if side == 2 { v = c.bottom }
  if side == 3 { v = c.left }
  if v == UI_AUTO or c.ex == null { return v }
  var p = c.ex.ip_t
  if side == 1 { p = c.ex.ip_r }
  if side == 2 { p = c.ex.ip_b }
  if side == 3 { p = c.ex.ip_l }
  return v + base * p / 100.0
}
# position: relative moves an element by its insets, a percentage taken of its parent's content box
function ly_nudge(n: UiNode, c: UiNode) -> void {
  let bw = n.cw - ly_hin(n)
  let bh = n.ch - ly_vin(n)
  ly_offset(c, ly_or0(ly_ins(c, 3, bw)) - ly_or0(ly_ins(c, 1, bw)), ly_or0(ly_ins(c, 0, bh)) - ly_or0(ly_ins(c, 2, bh)))
}