isHeightStretch property

@override bool get isHeightStretch

Implementation

@override
bool get isHeightStretch {
  RenderStyle renderStyle = this;
  CSSRenderStyle? parentRenderStyle = renderStyle.getAttachedRenderParentRenderStyle();
  if (parentRenderStyle == null) {
    return false;
  }

  // Stretching a flex item in the cross axis (height for row-direction flex)
  // only applies when the flex container’s cross size is definite. A merely
  // bounded (non-tight) maxHeight is not definite and must not force
  // height:auto items to expand to the available extent (e.g., in Sliver/ListView).
  final BoxConstraints? parentContentConstraints = parentRenderStyle.contentConstraints();
  // Note: avoid calling parentRenderStyle.constraints() here. When computing
  // styles for detached nodes (or before first layout), the parent may not
  // have an attached render box and constraints() can be null/throw.
  final bool parentHasDefiniteHeight =
      parentRenderStyle.height.isNotAuto || (parentContentConstraints?.hasTightHeight ?? false);

  bool isStretch = false;

  bool isParentFlex =
      parentRenderStyle.display == CSSDisplay.flex || parentRenderStyle.display == CSSDisplay.inlineFlex;
  bool isHorizontalDirection = false;
  bool isFlexNoWrap = false;
  bool isChildStretchSelf = false;
  if (isParentFlex) {
    // The absolutely-positioned box is considered to be “fixed-size”, a value of stretch
    // is treated the same as flex-start.
    // https://www.w3.org/TR/css-flexbox-1/#abspos-items
    bool isPositioned =
        renderStyle.position == CSSPositionType.absolute || renderStyle.position == CSSPositionType.fixed;
    if (isPositioned) {
      return false;
    }

    isHorizontalDirection = CSSFlex.isHorizontalFlexDirection(parentRenderStyle.flexDirection);
    isFlexNoWrap = parentRenderStyle.flexWrap != FlexWrap.wrap && parentRenderStyle.flexWrap != FlexWrap.wrapReverse;
    isChildStretchSelf = renderStyle.alignSelf != AlignSelf.auto
        ? renderStyle.alignSelf == AlignSelf.stretch
        : parentRenderStyle.alignItems == AlignItems.stretch;
  }

  CSSLengthValue marginTop = renderStyle.marginTop;
  CSSLengthValue marginBottom = renderStyle.marginBottom;

  // Display as block if flex vertical layout children and stretch children
  if (marginTop.isNotAuto &&
      marginBottom.isNotAuto &&
      isParentFlex &&
      isHorizontalDirection &&
      isFlexNoWrap &&
      isChildStretchSelf &&
      parentHasDefiniteHeight) {
    isStretch = true;
  }

  return isStretch;
}