anchor.diff:        );
   
         // Add a tap gesture to collapse the currently opened section.
  -      if (_state != _DemoState.normal) {
  -        demoContent = Semantics(
  -          label: MaterialLocalizations.of(context).modalBarrierDismissLabel,
  -          child: GestureDetector(
  -            behavior: HitTestBehavior.opaque,
  -            onTap: () {
  +      demoContent = Semantics(
  +        label: MaterialLocalizations.of(context).modalBarrierDismissLabel,
  +        child: GestureDetector(
  +          onTap: () {
  +            if (_state != _DemoState.normal) {
                 setStateAndUpdate(() {
                   _state = _DemoState.normal;
                 });
  -            },
  -            child: ExcludeSemantics(child: demoContent),
  -          ),
  -        );
  -      }
  +            }
  +          },
  +          child: Semantics(
  +            excludeSemantics: _state != _DemoState.normal,
  +            child: demoContent,
  +          ),
  +        ),
  +      );
   
         body = SafeArea(
           bottom: false,
  
positive.code:     final textTheme = Theme.of(context).textTheme;
      final colorScheme = Theme.of(context).colorScheme;
  
      return Container(
        padding: const EdgeInsetsDirectional.only(
          start: 24,
          top: 12,
          end: 24,
          bottom: 32,
        ),
        constraints: BoxConstraints(maxHeight: maxHeight),
        child: SingleChildScrollView(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(
                title,
                style: textTheme.display1.apply(
                  color: colorScheme.onSurface,
                  fontSizeDelta:
                      isDisplayDesktop(context) ? desktopDisplay1FontDelta : 0,
                ),
              ),
              SizedBox(height: 12),
              Text(
                description,
                style: textTheme.body1.apply(color: colorScheme.onSurface),
              ),
            ],
          ),
        ),
      );
  
negative.code:   const _DemoSectionOptions({
      Key key,
      this.maxHeight,
      this.maxWidth,
      this.configurations,
      this.configIndex,
      this.onConfigChanged,
    }) : super(key: key);
  
    final double maxHeight;
    final double maxWidth;
    final List<GalleryDemoConfiguration> configurations;
    final int configIndex;
    final ValueChanged<int> onConfigChanged;
  