Function startDrag

static/js/transport.js:266–281

(e, surface)

  let moved = false;

  const startDrag = (e, surface) => {
    if (e.button !== 0 || e.target.closest(".loop-region")) return;
    const t = timeFromClientX(e.clientX);
    if (t === null) return;
    dragging = true;
    activePointerId = e.pointerId;
    moved = false;
    dragStartTime = t;
    setLoopStart(t);
    setLoopEnd(t);
    setLoopEnabled(true);
    loopBtn.classList.add("active");
    updateLoopRegionVisual();
    surface.setPointerCapture(e.pointerId);
    e.preventDefault();
  };

  const moveDrag = (e) => {
    if (!dragging || e.pointerId !== activePointerId) return;