anchor.diff:    ///
     /// Snapping only applies when the app bar is floating, not when the appbar
     /// appears at the top of its scroll view.
  +  ///
  +  /// ## Animated Examples
  +  ///
  +  /// The following animations show how the app bar changes its scrolling
  +  /// behavior based on the value of this property.
  +  ///
  +  /// * App bar with [snap] set to false:
  +  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_floating.mp4}
  +  /// * App bar with [snap] set to true:
  +  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_floating_snap.mp4}
  +  ///
  +  /// See also:
  +  ///
  +  /// * [SliverAppBar] for more animated examples of how this property changes the
  +  ///   behavior of the app bar in combination with [pinned] and [floating].
     final bool snap;
   
     @override
  
positive.code:   /// If [snap] is true then a scroll that exposes the app bar will trigger an
    /// animation that slides the entire app bar into view. Similarly if a scroll
    /// dismisses the app bar, the animation will slide it completely out of view.
    final bool floating;
  
    /// Whether the app bar should remain visible at the start of the scroll view.
    ///
    /// The app bar can still expand and contract as the user scrolls, but it will
    /// remain visible rather than being scrolled out of view.
    final bool pinned;
  
    /// If [snap] and [floating] are true then the floating app bar will "snap"
  
negative.code: /// )
  /// ```
  /// {@end-tool}
  ///
  /// ## Animated Examples
  ///
  /// The following animations show how app bars with different configurations
  /// behave when a user scrolls up and then down again.
  ///
  /// * App bar with [floating]: false, [pinned]: false, [snap]: false:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar.mp4}
  ///
  /// * App bar with [floating]: true, [pinned]: false, [snap]: false:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_floating.mp4}
  ///
  /// * App bar with [floating]: true, [pinned]: false, [snap]: true:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_floating_snap.mp4}
  ///
  /// * App bar with [floating]: true, [pinned]: true, [snap]: false:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_pinned_floating.mp4}
  ///
  /// * App bar with [floating]: true, [pinned]: true, [snap]: true:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_pinned_floating_snap.mp4}
  ///
  /// * App bar with [floating]: false, [pinned]: true, [snap]: false:
  ///   {@animation 476 400 https://flutter.github.io/assets-for-api-docs/assets/material/app_bar_pinned.mp4}
  ///
  /// The property [snap] can only be set to true if [floating] is also true.
  ///
  /// See also:
  ///
  