Analisis ringkas tentang bagaimana Angular rxjs melaksanakan fungsi drag-and-drop?

<div id="anchor" #anchor>
  <div class="video" id="video" #video>
    <div class="masker"></div>
    <video width="100%" height="100%" controls poster="assets/poster.png">
      <source src="../assets/demo.mp4" type="video/mp4" />
      Your browser does not support.
    </video>
  </div>
</div>

<!-- styles.scss -->
<!-- 这部分需要放在全局样式中 -->
html, body {
  height: 6000px;
  background-color: #fff;
}

<!-- demo.component.scss -->

#anchor {
  height: 360px;
  width: 100%;
  background-color: #F0F0F0;
}

.video {
  width: 640px;
  height: 360px;
  margin: 0 auto;
  background-color: black;
  <!-- video fixed 布局的样式，默认布局中是没有的 -->
  &.video-fixed { 
    position: fixed;
    top: 10px;
    left: 10px;
    width: 320px;
    height: 150px;
    cursor: all-scroll;
    .masker {
         display: none;
      }
    &:hover {
      .masker {
        display: block;
        position: absolute;
        width: 100%;
        height: 100%;
        background-color: rgba(0, 0, 0, 0.8);
        z-index: 2;
      }
    }
  }
}

@ViewChild('anchor', { static: false })
public anchor!: ElementRef;
@ViewChild('video', { static: false })
public video!: ElementRef;

public scroll!: any;

ngAfterViewInit(): void {
  this.scroll = fromEvent(document, 'scroll');
  this.scrollFn();
}

// 页面滚动
public scrollFn() {
  this.scroll
    .pipe(
      debounceTime(50), // 防抖
      map(() => this.anchor.nativeElement.getBoundindClientRect().bottom < 0)
    )
    .subscribe((flag: boolean) => {
      // 添加和移除样式
      if(flag) {
        this.video.nativeElement.classList.add(&#39;video-fixed&#39;);
      } else {
        this.video.nativeElement.classList.remove(&#39;video-fixed&#39;);
      }
    })
}

// demo.component.ts

public mouseDown!: any;
public mouseUp!: any;
public mouseMove!: any;

ngAfterViewInit(): void {
  this.mouseDown = fromEvent(this.video.nativeElement, 'mousedown'); // 目标元素按下，即 video
  this.mouseMove = fromEvent(document, 'mousemove'); // 元素在文档内移动
  this.mouseUp = fromEvent(document, 'mouseup'); // 鼠标抬起
  
  this.moveFn()
}

// 目标元素移动
public moveFn() {
  this.mouseDown
    .pipe(
      filter(() => this.video.nativeElement.classList.contains('video-fixed')),
      map(() => this.mouseMove.pipe(
        throttleTime(50), // 节流
        takeUntil(this.mouseUp)
      )),
      // concatAll 顺序接受上游抛出的各个数据流作为它的数据， 若前面的数据流不能同步的完结，它会暂存后续数据流，当前数据流完成后它才会订阅后一个暂存的数据流
      concatAll(),
      withLatestFrom(this.mouseDown, (move:any, down:any) => {
        return {
          x: this.validValue(move.clientX - down.offsetX, window.innerWidth - this.video.nativeElement.offsetWidth, 0),
          y: this.validValue(move.clientY - down.offsetY, window.innerHeight - this.video.nativeElement.offsetHeight, 0)
        }
      })
    )
    .subscribe((position: {
      x: number,
      y: number
    }) => {
      this.video.nativeElement.style.top = position.y + 'px';
      this.video.nativeElement.style.left = position.x + 'px';
    })
}

// 校验边界值
public validValue = (value:number, max:number, min: number) => {
  return Math.min(Math.max(value, min), max)
}