Trait ContainerLayer

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pub trait ContainerLayer: Layer {
    const AS_OFFSET: Option<fn() -> &'static OffsetLayerVTable> = None;

    // Required methods
    fn container_layer_data(
        self: Handle<Self>,
        app: &App,
    ) -> &ContainerLayerData;
    fn container_layer_data_mut(
        self: Handle<Self>,
        app: &mut App,
    ) -> &mut ContainerLayerData;

    // Provided methods
    fn as_container_layer(self: Handle<Self>) -> AnyContainerLayer { ... }
    fn apply_transform(
        self: Handle<Self>,
        app: &App,
        child: Option<AnyLayer>,
        transform: &mut Matrix4,
    ) { ... }
    fn fire_composition_callbacks(
        self: Handle<Self>,
        app: &mut App,
        include_children: bool,
    ) { ... }
    fn supports_rasterization(self: Handle<Self>, app: &App) -> bool { ... }
    fn dispose(self: Handle<Self>, app: &mut App) { ... }
    fn find_annotations(
        self: Handle<Self>,
        app: &App,
        result: &mut AnnotationSearch,
        local_position: Offset,
        only_first: bool,
    ) -> bool { ... }
    fn attach(self: Handle<Self>, app: &mut App, owner: HandleId) { ... }
    fn detach(self: Handle<Self>, app: &mut App) { ... }
    fn redepth_children(self: Handle<Self>, app: &mut App) { ... }
    fn add_to_scene(
        self: Handle<Self>,
        app: &mut App,
        builder: &mut SceneBuilder,
    ) { ... }
}

Expand description

A composited layer that has a list of children.

A ContainerLayer instance merely takes a list of children and inserts them into the composited rendering in order. There are subclasses of ContainerLayer which apply more elaborate effects in the process.

Flutter’s ContainerLayer: the child list lives on AnyContainerLayer; this trait holds the virtual apply_transform and the bodies of the Layer methods it overrides. A leaf’s impl Layer forwards to them: fn attach(..) { ContainerLayer::attach(self, app, owner) }.

Provided Associated Constants§

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const AS_OFFSET: Option<fn() -> &'static OffsetLayerVTable> = None

The offset table when this type extends OffsetLayer; container_layer_accessors!(offset) sets it. Dart’s layer is OffsetLayer.

Required Methods§

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fn container_layer_data(self: Handle<Self>, app: &App) -> &ContainerLayerData

Mixin field access.

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fn container_layer_data_mut( self: Handle<Self>, app: &mut App, ) -> &mut ContainerLayerData

See container_layer_data.

Provided Methods§

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fn as_container_layer(self: Handle<Self>) -> AnyContainerLayer

Dart’s implicit upcast of a concrete layer to ContainerLayer.

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fn apply_transform( self: Handle<Self>, app: &App, child: Option<AnyLayer>, transform: &mut Matrix4, )

Applies the transform that would be applied when compositing the given child to the given matrix.

Specifically, this should apply the transform that is applied to child’s origin. When using apply_transform with a chain of layers, results will be unreliable unless the deepest layer in the chain collapses the layerOffset in add_to_scene to zero, meaning that it passes Offset::ZERO to its children, and bakes any incoming layerOffset into the SceneBuilder as (for instance) a transform (which is then also included in the transformation applied by apply_transform).

This method is only valid immediately after add_to_scene has been called, before any of the properties have been changed.

The default implementation does nothing, since ContainerLayer, by default, composites its children at the origin of the ContainerLayer itself.

The child argument should generally not be None, since in principle a layer could transform each child independently. However, certain layers may explicitly allow None as a value, for example if they know that they transform all their children identically.

Used by FollowerLayer to transform its child to a LeaderLayer’s position.

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