"PointerEvent cancel：pointercancel 与手势恢复"

概述`pointercancel` 在指针活动被系统打断时触发（如滚动、系统手势、设备变更），应用应停止当前手势、清理状态并允许下次重启，避免残留捕获与异常路径。示例const el = document.getElementById('canvas') el.addEventListener('pointerdown', e => start(e)) el.addEventListener('pointermove', e => move(e)) el.addEventListener('pointerup', e => end(e)) el.addEventListener('pointercancel', e => cancel(e)) function cancel(e){ resetGesture(); el.releasePointerCapture?.(e.pointerId) } 工程建议捕获与合并：结合 `setPointerCapture` 与 `getCoalescedEvents()`；在取消时释放捕获与队列。与触控滚动：设置 `touch-action` 准确声明手势与滚动关系；避免冲突。兼容：在旧浏览器回退到 `touchcancel`/`mouseleave` 等事件；保持一致逻辑。参考与验证MDN Pointer Events 文档：https://developer.mozilla.org/docs/Web/API/Pointer_events