Function getOverflowState

javascript/atoms/typescript/is-displayed.ts:244–366

(elem: Element)

  }

  function getOverflowState(elem: Element): OverflowState {
    var region = getClientRegion(elem);
    var ownerDoc = elem.ownerDocument;
    var htmlElem = ownerDoc.documentElement;
    var bodyElem = ownerDoc.body;
    var htmlOverflowStyle = getEffectiveStyle(htmlElem, 'overflow') || 'visible';
    var treatAsFixedPosition = false;

    function canBeOverflowed(container: Element, position: string | null): boolean {
      if (container === htmlElem) {
        return true;
      }

      var display = getEffectiveStyle(container, 'display') || '';
      if (display.indexOf('inline') === 0 || display === 'contents') {
        return false;
      }

      if (position === 'absolute' && getEffectiveStyle(container, 'position') === 'static') {
        return false;
      }

      return true;
    }

    function getOverflowParent(current: Element): Element | null {
      var position = getEffectiveStyle(current, 'position');
      if (position === 'fixed') {
        treatAsFixedPosition = true;
        return current === htmlElem ? null : htmlElem;
      }

      var parent = getParentElement(current);
      while (parent && !canBeOverflowed(parent, position)) {
        parent = getParentElement(parent);
      }
      return parent;
    }

    function getOverflowStyles(current: Element): OverflowStyles {
      var overflowElem = current;
      if (htmlOverflowStyle === 'visible') {
        if (current === htmlElem && bodyElem) {
          overflowElem = bodyElem;
        } else if (current === bodyElem) {
          return { x: 'visible', y: 'visible' };
        }
      }

      var overflow = {
        x: getEffectiveStyle(overflowElem, 'overflow-x') || 'visible',
        y: getEffectiveStyle(overflowElem, 'overflow-y') || 'visible',
      };

      if (current === htmlElem) {
        overflow.x = overflow.x === 'visible' ? 'auto' : overflow.x;
        overflow.y = overflow.y === 'visible' ? 'auto' : overflow.y;
      }