PositionStrategy 位置策略

export interface PositionStrategy {  /** Attaches this position strategy to an overlay. */  attach(overlayRef: OverlayRef): void;  /** Updates the position of the overlay element. */  apply(): void;  /** Called when the overlay is detached. */  detach?(): void;  /** Cleans up any DOM modifications made by the position strategy, if necessary. */  dispose(): void;}复制代码

OverlayPositionBuilder 位置策略创建者

// 获取全局定位global(): GlobalPositionStrategy;// 创建flexible定位flexibleConnectedTo(elementRef: ElementRef | HTMLElement): FlexibleConnectedPositionStrategy;复制代码

GlobalPositionStrategy 全局

// 上右下左 宽高 水平，垂直top().right().bottom().left().width().height().centerHorizontally().centerVertically()复制代码

FlexibleConnectedPositionStrategy flexible

isElementScrolledOutsideView 是否在滚出试图范围内

export function isElementScrolledOutsideView(element: ClientRect, scrollContainers: ClientRect[]) {  return scrollContainers.some(containerBounds => {    const outsideAbove = element.bottom < containerBounds.top;    const outsideBelow = element.top > containerBounds.bottom;    const outsideLeft = element.right < containerBounds.left;    const outsideRight = element.left > containerBounds.right;    return outsideAbove || outsideBelow || outsideLeft || outsideRight;  });}复制代码

isElementClippedByScrolling 是否被剪切

export function isElementClippedByScrolling(element: ClientRect, scrollContainers: ClientRect[]) {  return scrollContainers.some(scrollContainerRect => {    const clippedAbove = element.top < scrollContainerRect.top;    const clippedBelow = element.bottom > scrollContainerRect.bottom;    const clippedLeft = element.left < scrollContainerRect.left;    const clippedRight = element.right > scrollContainerRect.right;    return clippedAbove || clippedBelow || clippedLeft || clippedRight;  });}复制代码