hitTestChildren method

  1. @override
  2. @protected
bool hitTestChildren(
  1. BoxHitTestResult result, {
  2. required Offset position,
})
override

Override this method to check whether any children are located at the given position.

Subclasses should return true if at least one child reported a hit at the specified position.

Typically children should be hit-tested in reverse paint order so that hit tests at locations where children overlap hit the child that is visually "on top" (i.e., paints later).

The caller is responsible for transforming position from global coordinates to its location relative to the origin of this RenderBox. Likewise, this RenderBox is responsible for transforming the position that it passes to its children when it calls hitTest on each child.

If transforming is necessary, BoxHitTestResult.addWithPaintTransform, BoxHitTestResult.addWithPaintOffset, or BoxHitTestResult.addWithRawTransform need to be invoked by subclasses to record the required transform operations in the BoxHitTestResult. These methods will also help with applying the transform to position.

Used by hitTest. If you override hitTest and do not call this function, then you don't need to implement this function.

Implementation

@override
@protected
bool hitTestChildren(BoxHitTestResult result, { required Offset position }) {
  final Offset effectivePosition = position - _paintOffset;
  final GlyphInfo? glyph = _textPainter.getClosestGlyphForOffset(effectivePosition);
  // The hit-test can't fall through the horizontal gaps between visually
  // adjacent characters on the same line, even with a large letter-spacing or
  // text justification, as graphemeClusterLayoutBounds.width is the advance
  // width to the next character, so there's no gap between their
  // graphemeClusterLayoutBounds rects.
  final InlineSpan? spanHit = glyph != null && glyph.graphemeClusterLayoutBounds.contains(effectivePosition)
    ? _textPainter.text!.getSpanForPosition(TextPosition(offset: glyph.graphemeClusterCodeUnitRange.start))
    : null;
  switch (spanHit) {
    case final HitTestTarget span:
      result.add(HitTestEntry(span));
      return true;
    case _:
      return hitTestInlineChildren(result, effectivePosition);
  }
}