Function seek

static/mobile/app.js:816–824

(cx)

      const rect = bars.getBoundingClientRect();
      const head = bars.querySelector(".playhead");
      const seek = (cx) => {
        const frac = Math.max(0, Math.min(1, (cx - rect.left) / rect.width));
        if (head) head.style.left = frac * 100 + "%";
        const cur = app.querySelector(".wave-times .cur");
        if (cur) cur.textContent = fmt(frac * curDuration());
        state.progress = frac;
        paintWaveProgress();
        seekToFraction(frac);
      };
      seek(e.clientX);
      bars.setPointerCapture(e.pointerId);
      const mv = (ev) => seek(ev.clientX);