| 61 | let stable = 0; |
| 62 | let frames = 0; |
| 63 | const tick = () => { |
| 64 | if (done) return; |
| 65 | frames += 1; |
| 66 | if (frames > MAX_FRAMES) { |
| 67 | el.scrollTop = top; // 布局迟迟不稳：精确还原一次后收手 |
| 68 | settle(); |
| 69 | return; |
| 70 | } |
| 71 | const h = el.scrollHeight; |
| 72 | if (h === last) { |
| 73 | stable += 1; |
| 74 | if (stable >= STABLE_FRAMES) { |
| 75 | el.scrollTop = top; // 布局稳定 → 精确还原 |
| 76 | settle(); |
| 77 | return; |
| 78 | } |
| 79 | } else { |
| 80 | last = h; |
| 81 | stable = 0; |
| 82 | el.scrollTop = top; // 仍在长高 → 每帧跟随目标，减少跳动 |
| 83 | } |
| 84 | requestAnimationFrame(tick); |
| 85 | }; |
| 86 | requestAnimationFrame(tick); |
| 87 | |
| 88 | return settle; |