RawMenuAnchor class

A widget that wraps a child and anchors a floating menu.

The child can be any widget, but is typically a button, a text field, or, in the case of context menus, the entire screen.

The menu overlay of a RawMenuAnchor is shown by calling MenuController.open on an attached MenuController.

When a RawMenuAnchor is opened, overlayBuilder is called to construct the menu contents within an Overlay. The Overlay allows the menu to "float" on top of other widgets. The info argument passed to overlayBuilder provides the anchor's Rect, the Size of the overlay, the TapRegion.groupId used by members of the menu system, and the position argument passed to MenuController.open.

If MenuController.open is called with a position argument, it will be passed to the info argument of the overlayBuilder function.

The RawMenuAnchor does not manage semantics and focus of the menu.

Adding animations to menus

A RawMenuAnchor has no knowledge of animations, as evident from its APIs, which don't involve AnimationController at all. It only knows whether the overlay is shown or hidden.

If another widget intends to implement a menu with opening and closing transitions, RawMenuAnchor's overlay should remain visible throughout both the opening and closing animation durations.

This means that the showOverlay callback passed to onOpenRequested should be called before the first frame of the opening animation. Conversely, hideOverlay within onCloseRequested should only be called after the closing animation has completed.

This also means that, if MenuController.open is called while the overlay is already visible, RawMenuAnchor has no way of knowing whether the menu is currently opening, closing, or stably displayed. The parent widget will need to manage additional information (such as the state of an AnimationController) to determine how to respond in such scenarios.

To programmatically control a RawMenuAnchor, like opening or closing it, or checking its state, you can get its associated MenuController. Use MenuController.maybeOf(BuildContext context) to retrieve the controller for the closest RawMenuAnchor ancestor of a given BuildContext. More detailed usage of MenuController is available in its class documentation.