scrollYListener method

Implementation

void scrollYListener() {
  assert(scrollListener != null);
  if (scrollOffsetY != null) {
    if (DebugFlags.debugLogScrollableEnabled) {
      final double maxY = math.max(0.0, (_scrollableSize?.height ?? 0) - (_viewportSize?.height ?? 0));
      renderingLogger.finer('[Overflow-Scroll] <${renderStyle.target.tagName.toLowerCase()}> Y pixels='
          '${scrollOffsetY!.pixels.toStringAsFixed(2)} max=${maxY.toStringAsFixed(2)}');
    }
    scrollListener!(scrollOffsetY!.pixels, AxisDirection.down);
    if (DebugFlags.debugLogSemanticsEnabled || DebugFlags.debugLogScrollableEnabled) {
      debugPrint('[webf][a11y][scroll] ${renderStyle.target} '
          'scrollY=${scrollOffsetY!.pixels.toStringAsFixed(2)} '
          'viewport=${_viewportSize?.height.toStringAsFixed(1) ?? '?'} '
          'content=${_scrollableSize?.height.toStringAsFixed(1) ?? '?'} '
          '→ markNeedsSemanticsUpdate');
    }
    markNeedsSemanticsUpdate();
    markNeedsPaint();
  }
}