Draggable window in _hyperscript

Draggable._hs

-- Usage: _="install Draggable(dragHandle: .titlebar in me)"

behavior Draggable(dragHandle)
  init
    if no dragHandle set the dragHandle to me
  end
  on pointerdown(clientX, clientY) from dragHandle
    halt the event
    trigger draggable:start -- hooks, e.g. for adding a drop shadow while dragging
    measure my x, y
    set xoff to clientX - x
    set yoff to clientY - y
    repeat until event pointerup from document
      wait for pointermove(pageX, pageY) or
               pointerup  (pageX, pageY) from document
      add { left: ${pageX - xoff}px; top: ${pageY - yoff}px; }
      trigger draggable:move
    end
    trigger draggable:end
end