# ui_scrollbar.ludic — a scroll box's bar held and dragged: a press on the thumb holds it where it
# was taken, the pointer held moves it in proportion, letting go leaves it; a press on the track
# jumps the thumb's middle there; the wheel still scrolls; and the rows under the bar are never pressed.
import "ludic.ui"
import "ui_scrollbar_parts/Long.ludic"
program UiScrollbar {
  numbers float
  state UiScrollbarState {
    bx: float = 0.0
    by: float = 0.0
  }
  function frame(ui_st: mut UiState, i: UiInput) -> UiNode {
    ui_input(ui_st, i)
    ui_show(ui_st, "Long", null, 0.0, 0.0, 400.0, 400.0)
    let root: UiNode = ui_nodes(ui_st, "Long", null)
    ui_place(ui_st, root, 0.0, 0.0, 400.0, 400.0)
    return root.children[0]
  }
  # the pointer at (bx + x, by + y), held or not; how far the box is scrolled then
  function at(ui_scrollbar_st: UiScrollbarState, ui_st: mut UiState, x: float, y: float, down: bool) -> int {
    let i = new UiInput
    i.x = ui_scrollbar_st.bx + x
    i.y = ui_scrollbar_st.by + y
    i.down = down
    return int(frame(ui_st, i).children[0].scroll_y)
  }
  function wheel(ui_scrollbar_st: UiScrollbarState, ui_st: mut UiState, x: float, y: float) -> int {
    let i = new UiInput
    i.x = ui_scrollbar_st.bx + x
    i.y = ui_scrollbar_st.by + y
    i.wheel = 1.0
    frame(ui_st, i)
    return int(frame(ui_st, new UiInput).children[0].scroll_y)
  }
  entry (ui_scrollbar_st: mut UiScrollbarState, ui_st: mut UiState) {
    ui_backend(ui_st, new UiBackend)
    let list = frame(ui_st, new UiInput).children[0]
    ui_scrollbar_st.bx = list.x
    ui_scrollbar_st.by = list.y
    let grab = at(ui_scrollbar_st, ui_st, 195.0, 10.0, true)
    let moved = at(ui_scrollbar_st, ui_st, 195.0, 40.0, true)
    let far = at(ui_scrollbar_st, ui_st, 195.0, 300.0, true)
    let back = at(ui_scrollbar_st, ui_st, 195.0, 25.0, true)
    let kept = at(ui_scrollbar_st, ui_st, 195.0, 25.0, false)
    at(ui_scrollbar_st, ui_st, 0.0 - ui_scrollbar_st.bx - 1.0, 0.0 - ui_scrollbar_st.by - 1.0, false)
    let jump = at(ui_scrollbar_st, ui_st, 195.0, 80.0, true)
    at(ui_scrollbar_st, ui_st, 195.0, 80.0, false)
    let wheeled = wheel(ui_scrollbar_st, ui_st, 50.0, 50.0)
    at(ui_scrollbar_st, ui_st, 50.0, 20.0, true)
    at(ui_scrollbar_st, ui_st, 50.0, 20.0, false)
    let page = frame(ui_st, new UiInput)
    print(`grab {grab} moved {moved} far {far} back {back} kept {kept} | jump {jump} | wheel {wheeled} | {page.children[1].text}`)
  }
}