setUpChildBaselineForBFC method

Implementation

void setUpChildBaselineForBFC() {
  // Cache CSS baselines for non-IFC flow: use line metrics when overflow is visible.
  final paddingTop = renderStyle.paddingTop.computedValue;
  final borderTop = renderStyle.effectiveBorderTopWidth.computedValue;
  final bool overflowVisible = renderStyle.effectiveOverflowX == CSSOverflowType.visible &&
      renderStyle.effectiveOverflowY == CSSOverflowType.visible;
  double? firstBaseline;
  double? lastBaseline;

  // Special handling for inline-block elements
  if (renderStyle.display == CSSDisplay.inlineBlock && boxSize != null) {
    // Search for in-flow descendants that expose a CSS baseline:
    //  - Prefer inline formatting contexts (line boxes) when present.
    //  - Otherwise, use flex/grid container baselines if available.
    // If none exist anywhere inside, synthesize from the bottom margin edge.
    double? descendantBaseline = _findDescendantBaseline();
    if (descendantBaseline != null) {
      firstBaseline = descendantBaseline;
      lastBaseline = descendantBaseline;
    } else {
      final double marginBottom = renderStyle.marginBottom.computedValue;
      firstBaseline = boxSize!.height + marginBottom;
      lastBaseline = firstBaseline;
    }
  } else if (overflowVisible && _lineMetrics.isNotEmpty) {
    if (_lineMetrics.first.baseline != null) {
      firstBaseline = _lineMetrics.first.baseline! + paddingTop + borderTop;
    }
    double yOffset = 0;
    for (int i = 0; i < _lineMetrics.length; i++) {
      final line = _lineMetrics[i];
      if (line.baseline != null) {
        lastBaseline = yOffset + line.baseline! + paddingTop + borderTop;
      }
      if (i < _lineMetrics.length - 1) {
        yOffset += line.crossAxisExtent;
      }
    }
  } else if (boxSize != null) {
    // No in-flow line boxes found: per CSS 2.1 §10.8.1, synthesize baseline from
    // the bottom margin edge for block-level boxes.
    final double marginBottom = renderStyle.marginBottom.computedValue;
    firstBaseline = boxSize!.height + marginBottom;
    lastBaseline = firstBaseline;
  }
  setCssBaselines(first: firstBaseline, last: lastBaseline);
}