trackVisibility property
final
Indicates that the scrollbar track should be visible.
When true, the scrollbar track will always be visible so long as the thumb is visible. If the scrollbar thumb is not visible, the track will not be visible either.
Defaults to false when null.
If this property is null, then ScrollbarThemeData.trackVisibility of ThemeData.scrollbarTheme is used. If that is also null, the default value is false.
If the track visibility is related to the scrollbar's material state, use the global ScrollbarThemeData.trackVisibility or override the sub-tree's theme data.
Implementation
final bool? trackVisibility;