Struct bevy_quill::ViewAdapter

pub struct ViewAdapter<V>
where
    V: View,
{ /* private fields */ }

A ViewAdapter is a stateless object that can be used to access an object implementing View in a type-erased fashion, without needing to store a dyn View. This allows querying for ECS components that contain implementations of the View trait without knowing the concrete type. Note that it must be stateless since it is created statically, and passed around by static reference.

In order for this to work, two ECS components are needed: ViewThunk and a second component to actually hold the concrete view, such as ViewStateCell.

ViewThunk is a type-erased component that provides access to the concrete View via the ViewAdapter. ViewStateCell is a component that contains the actual View and it’s state. Because ViewStateCell is generic, it cannot be queried directly (since it would require a separate query for every specialization), so we use ViewThunk as an adapter. ViewAdapter also can work with other component types that contain a View implementation.

The the methods of ViewAdapter and ViewThunk take an entity id to identify the view rather than self``; the self` parameter is only there to make the methods dyn-trait compatible. This allows the adapter to be created as a static object, since all of its state is external.

See AnyViewAdapter and ViewThunk.

Trait Implementations

impl<V> AnyViewAdapter for ViewAdapter<V>

where V: View,

fn nodes(&self, world: &mut World, entity: Entity) -> NodeSpan

Return the span of entities produced by this View.

fn rebuild( &self, world: &mut World, entity: Entity, scope: &mut TrackingScope, ) -> bool

Update the internal state of this view, re-creating any UiNodes. Returns true if the output changed, that is, if nodes() would return a different value than it did before the rebuild.

fn raze(&self, world: &mut World, entity: Entity)

Recursively despawn any child entities that were created as a result of calling .build(). This calls .raze() for any nested views within the current view state.

fn attach_children(&self, world: &mut World, entity: Entity) -> bool

Instructs the view to attach any child entities to the parent entity. This is called whenever we know that one or more child entities have changed.