assembleSemanticsNode method

  1. @override
void assembleSemanticsNode(
  1. SemanticsNode node,
  2. SemanticsConfiguration config,
  3. Iterable<SemanticsNode> children
)
override

Assemble the SemanticsNode for this RenderObject.

If describeSemanticsConfiguration sets SemanticsConfiguration.isSemanticBoundary to true, this method is called with the node created for this RenderObject, the config to be applied to that node and the children SemanticsNodes that descendants of this RenderObject have generated.

By default, the method will annotate node with config and add the children to it.

Subclasses can override this method to add additional SemanticsNodes to the tree. If new SemanticsNodes are instantiated in this method they must be disposed in clearSemantics.

Implementation

@override
void assembleSemanticsNode(SemanticsNode node, SemanticsConfiguration config, Iterable<SemanticsNode> children) {
  assert(_semanticsInfo != null && _semanticsInfo!.isNotEmpty);
  final List<SemanticsNode> newChildren = <SemanticsNode>[];
  TextDirection currentDirection = textDirection;
  Rect currentRect;
  double ordinal = 0.0;
  int start = 0;
  int placeholderIndex = 0;
  int childIndex = 0;
  RenderBox? child = firstChild;
  final LinkedHashMap<Key, SemanticsNode> newChildCache = LinkedHashMap<Key, SemanticsNode>();
  _cachedCombinedSemanticsInfos ??= combineSemanticsInfo(_semanticsInfo!);
  for (final InlineSpanSemanticsInformation info in _cachedCombinedSemanticsInfos!) {
    final TextSelection selection = TextSelection(
      baseOffset: start,
      extentOffset: start + info.text.length,
    );
    start += info.text.length;

    if (info.isPlaceholder) {
      // A placeholder span may have 0 to multiple semantics nodes, we need
      // to annotate all of the semantics nodes belong to this span.
      while (children.length > childIndex &&
             children.elementAt(childIndex).isTagged(PlaceholderSpanIndexSemanticsTag(placeholderIndex))) {
        final SemanticsNode childNode = children.elementAt(childIndex);
        final TextParentData parentData = child!.parentData! as TextParentData;
        // parentData.scale may be null if the render object is truncated.
        if (parentData.offset != null) {
          newChildren.add(childNode);
        }
        childIndex += 1;
      }
      child = childAfter(child!);
      placeholderIndex += 1;
    } else {
      final TextDirection initialDirection = currentDirection;
      final List<ui.TextBox> rects = getBoxesForSelection(selection);
      if (rects.isEmpty) {
        continue;
      }
      Rect rect = rects.first.toRect();
      currentDirection = rects.first.direction;
      for (final ui.TextBox textBox in rects.skip(1)) {
        rect = rect.expandToInclude(textBox.toRect());
        currentDirection = textBox.direction;
      }
      // Any of the text boxes may have had infinite dimensions.
      // We shouldn't pass infinite dimensions up to the bridges.
      rect = Rect.fromLTWH(
        math.max(0.0, rect.left),
        math.max(0.0, rect.top),
        math.min(rect.width, constraints.maxWidth),
        math.min(rect.height, constraints.maxHeight),
      );
      // round the current rectangle to make this API testable and add some
      // padding so that the accessibility rects do not overlap with the text.
      currentRect = Rect.fromLTRB(
        rect.left.floorToDouble() - 4.0,
        rect.top.floorToDouble() - 4.0,
        rect.right.ceilToDouble() + 4.0,
        rect.bottom.ceilToDouble() + 4.0,
      );
      final SemanticsConfiguration configuration = SemanticsConfiguration()
        ..sortKey = OrdinalSortKey(ordinal++)
        ..textDirection = initialDirection
        ..attributedLabel = AttributedString(info.semanticsLabel ?? info.text, attributes: info.stringAttributes);
      switch (info.recognizer) {
        case TapGestureRecognizer(onTap: final VoidCallback? handler):
        case DoubleTapGestureRecognizer(onDoubleTap: final VoidCallback? handler):
          if (handler != null) {
            configuration.onTap = handler;
            configuration.isLink = true;
          }
        case LongPressGestureRecognizer(onLongPress: final GestureLongPressCallback? onLongPress):
          if (onLongPress != null) {
            configuration.onLongPress = onLongPress;
          }
        case null:
          break;
        default:
          assert(false, '${info.recognizer.runtimeType} is not supported.');
      }
      if (node.parentPaintClipRect != null) {
        final Rect paintRect = node.parentPaintClipRect!.intersect(currentRect);
        configuration.isHidden = paintRect.isEmpty && !currentRect.isEmpty;
      }
      final SemanticsNode newChild;
      if (_cachedChildNodes?.isNotEmpty ?? false) {
        newChild = _cachedChildNodes!.remove(_cachedChildNodes!.keys.first)!;
      } else {
        final UniqueKey key = UniqueKey();
        newChild = SemanticsNode(
          key: key,
          showOnScreen: _createShowOnScreenFor(key),
        );
      }
      newChild
        ..updateWith(config: configuration)
        ..rect = currentRect;
      newChildCache[newChild.key!] = newChild;
      newChildren.add(newChild);
    }
  }
  // Makes sure we annotated all of the semantics children.
  assert(childIndex == children.length);
  assert(child == null);

  _cachedChildNodes = newChildCache;
  node.updateWith(config: config, childrenInInversePaintOrder: newChildren);
}