# pointer_events.ludic - on-pointerdown, on-pointermove, on-pointerup, on-wheel and on-drag on any
# element, with event.x / event.y inside it, event.dx / event.dy, event.button and event.wheel; a
# native takes the same through ui_native_input. A press captures the pointer until it is let go.
export property UiPointer {
  kind: string = ""             # pointerdown, pointermove, pointerup, wheel or drag
  x: float = 0.0                # inside the element
  y: float = 0.0
  dx: float = 0.0               # how far the pointer moved this frame
  dy: float = 0.0
  button: int = 0               # 0 the left button, 1 the right, 2 the middle
  wheel: float = 0.0
}
const PE_NAMES: string = " pointerdown pointermove pointerup wheel drag "
function pe_wants(n: UiNode, wheel: bool) -> bool {
  if n.kind == UI_NATIVE and n.native != null and n.native.input != null { return true }
  if n.on_names == null { return false }
  for i in 0 .. len(n.on_names) {
    if wheel and n.on_names[i] == "wheel" { return true }
    if not wheel and lk_in(PE_NAMES, n.on_names[i]) { return true }
  }
  return false
}
# the pointer's events this frame: to what captured it, else to what it is over
function pe_frame(ui_st: mut UiState, root: UiNode, scope: UiNode) -> void {
  let i = ui_st.in_now
  let p = ui_st.in_last
  let moved = p.x >= 0.0 and (i.x != p.x or i.y != p.y)
  var over: UiNode = null
  if fr_in(scope, i.x, i.y) { over = fr_pick(scope, i.x, i.y, PK_POINTER) }
  if ui_st.pe_key != "" {
    let c = fr_node(root, ui_st.pe_key)
    if c != null and moved { pe_send(ui_st, c, "pointermove", ui_st.pe_btn) }
    if c != null and moved { pe_send(ui_st, c, "drag", ui_st.pe_btn) }
    if not (i.down or i.down_right or i.down_middle) {
      if c != null { pe_send(ui_st, c, "pointerup", ui_st.pe_btn) }
      ui_st.pe_key = ""
    }
  } else if over != null {
    let b = pe_pressed(i, p)
    if b >= 0 { pe_down(ui_st, over, b) } else if moved { pe_send(ui_st, over, "pointermove", 0) }
  }
  if i.wheel != 0.0 and over != null { pe_send(ui_st, over, "wheel", 0) }
}
function pe_pressed(i: UiInput, p: UiInput) -> int {
  if i.down and not p.down { return 0 }
  if i.down_right and not p.down_right { return 1 }
  if i.down_middle and not p.down_middle { return 2 }
  return -1
}
function pe_down(ui_st: mut UiState, n: UiNode, b: int) -> void {
  ui_st.pe_key = n.key
  ui_st.pe_btn = b
  if not pe_send(ui_st, n, "pointerdown", b) { ui_st.pe_key = "" }
}
# one event: a native's input answers at once (false: not its to take); an element's on-<kind> runs
# once the frame is drawn, with the pointer's fields on `event`
function pe_send(ui_st: mut UiState, n: UiNode, kind: string, b: int) -> bool {
  let e = ui_st.pe_evs[ui_st.pe_at]
  let v = ui_st.pe_vals[ui_st.pe_at]
  ui_st.pe_at = (ui_st.pe_at + 1) % PE_RING
  e.dx = 0.0
  e.dy = 0.0
  e.kind = kind
  e.x = ui_st.in_now.x - n.x
  e.y = ui_st.in_now.y - n.y
  if ui_st.in_last.x >= 0.0 {
    e.dx = ui_st.in_now.x - ui_st.in_last.x
    e.dy = ui_st.in_now.y - ui_st.in_last.y
  }
  e.button = b
  e.wheel = ui_st.in_now.wheel
  if n.kind == UI_NATIVE and n.native != null and n.native.input != null { return n.native.input(n, e) }
  Value.be_float(Value.get(v, "x"), e.x)
  Value.be_float(Value.get(v, "y"), e.y)
  Value.be_float(Value.get(v, "dx"), e.dx)
  Value.be_float(Value.get(v, "dy"), e.dy)
  Value.be_int(Value.get(v, "button"), b)
  Value.be_float(Value.get(v, "wheel"), e.wheel)
  ui_fire(ui_st, n, kind, v)
  return true
}
# a scroll box leaves the wheel to what is under the pointer inside it and takes it itself
function pe_takes_wheel(box: UiNode, px: float, py: float) -> bool {
  let t = fr_pick(box, px, py, PK_WHEEL)
  return t != null and t != box
}