beforeLayout method

Implementation

void beforeLayout() {
  final RenderObject? effectiveParent = parent is RenderEventListener ? (parent as RenderEventListener).parent : parent;
  // In WebF's render tree, CSS boxes can be wrapped by Flutter proxy render objects
  // (e.g., semantics/gesture/scroll adapters). Those wrappers can break the direct
  // "parent is RenderBoxModel" check, even though the incoming constraints are
  // already the correct containing-block size (e.g., grid/flex cell width).
  //
  // Prefer the incoming constraints whenever they are definite (tight) or when
  // we are in a normal CSS parent-child relationship. Flutter proxy parents
  // (e.g., Semantics/Scrollable) may still pass tight constraints that represent
  // the real containing block size (like grid/flex cells).
  //
  // Avoid using merely *bounded* constraints from Flutter layout (e.g. Column),
  // because that can unintentionally clamp shrink-to-fit widget elements like
  // `<flutter-button>` and make them expand to maxWidth.
  final bool shouldUseIncomingConstraints =
      effectiveParent is RenderBoxModel || constraints.hasTightWidth || constraints.hasTightHeight;
  BoxConstraints contentConstraints = shouldUseIncomingConstraints ? constraints : getConstraints();

  // When a parent enforces a definite border-box size (e.g., grid/flex cell),
  // treat that as the used size for resolving this element's "auto" sizing.
  // This ensures descendants resolve percentages and auto widths against the
  // actual containing block size, even when CSS boxes are wrapped by Flutter
  // proxy render objects (Scrollable/Semantics/etc.).
  if (shouldUseIncomingConstraints &&
      constraints.hasTightWidth &&
      constraints.maxWidth.isFinite &&
      renderStyle.width.isAuto &&
      // Do not force a definite auto width on flex items. Flex items' main-axis
      // size is resolved by the flex formatting context; forcing auto width to
      // the container's tight constraint here breaks flex base sizing and can
      // collapse sibling flex items (e.g., overflow:hidden + min-width:0 text truncation).
      !renderStyle.isParentRenderFlexLayout() &&
      renderStyle.position != CSSPositionType.absolute &&
      renderStyle.position != CSSPositionType.fixed) {
    double contentW = renderStyle.deflatePaddingBorderWidth(constraints.maxWidth);
    if (contentW.isFinite && contentW < 0) contentW = 0;
    renderStyle.contentBoxLogicalWidth = contentW;
    hasOverrideContentLogicalWidth = true;
  }
  if (shouldUseIncomingConstraints &&
      constraints.hasTightHeight &&
      constraints.maxHeight.isFinite &&
      renderStyle.height.isAuto &&
      // See width note above: do not force auto sizes for flex items.
      !renderStyle.isParentRenderFlexLayout() &&
      renderStyle.position != CSSPositionType.absolute &&
      renderStyle.position != CSSPositionType.fixed) {
    double contentH = renderStyle.deflatePaddingBorderHeight(constraints.maxHeight);
    if (contentH.isFinite && contentH < 0) contentH = 0;
    renderStyle.contentBoxLogicalHeight = contentH;
    hasOverrideContentLogicalHeight = true;
  }

  // Deflate border constraints.
  contentConstraints =
      renderStyle.deflateBorderConstraints(contentConstraints);
  // Deflate padding constraints.
  contentConstraints =
      renderStyle.deflatePaddingConstraints(contentConstraints);

  // Fix for text-overflow ellipsis: when content constraints become unbounded
  // but the original constraints were bounded, and the element needs ellipsis,
  // restore bounded width to allow proper text truncation.
  if (renderStyle.effectiveOverflowX != CSSOverflowType.visible &&
      renderStyle.effectiveTextOverflow == TextOverflow.ellipsis &&
      contentConstraints.maxWidth.isInfinite &&
      constraints.hasBoundedWidth) {
    // Recalculate the content constraints using the original bounded constraints
    BoxConstraints boundedConstraints =
        renderStyle.deflateBorderConstraints(constraints);
    boundedConstraints =
        renderStyle.deflatePaddingConstraints(boundedConstraints);

    contentConstraints = BoxConstraints(
      minWidth: contentConstraints.minWidth,
      maxWidth: boundedConstraints.maxWidth,
      minHeight: contentConstraints.minHeight,
      maxHeight: contentConstraints.maxHeight,
    );
  }

  this.contentConstraints = contentConstraints;
  clearOverflowLayout();
  isSelfSizeChanged = false;

  // Reset cached CSS baselines before a new layout pass. They will be
  // updated by subclasses that can establish inline formatting context
  // or have well-defined CSS baselines (e.g., replaced elements).
  _cssFirstBaseline = null;
  _cssLastBaseline = null;
}