Struct accesskit::TreeUpdate

pub struct TreeUpdate {
    pub nodes: Vec<(NodeId, Node)>,
    pub tree: Option<Tree>,
    pub focus: Option<NodeId>,
}

A serializable representation of an atomic change to a Tree.

The sender and receiver must be in sync; the update is only meant to bring the tree from a specific previous state into its next state. Trying to apply it to the wrong tree should immediately panic.

Note that for performance, an update should only include nodes that are new or changed. AccessKit platform adapters will avoid raising extraneous events for nodes that have not changed since the previous update, but there is still a cost in processing these nodes and replacing the previous instances.

Fields

nodes: Vec<(NodeId, Node)>

Zero or more new or updated nodes. Order doesn’t matter.

Each node in this list will overwrite any existing node with the same ID. This means that when updating a node, fields that are unchanged from the previous version must still be set to the same values as before.

It is an error for any node in this list to not be either the root or a child of another node. For nodes other than the root, the parent must be either an unchanged node already in the tree, or another node in this list.

To add a child to the tree, the list must include both the child and an updated version of the parent with the child’s ID added to Node::children.

To remove a child and all of its descendants, this list must include an updated version of the parent node with the child’s ID removed from Node::children. Neither the child nor any of its descendants may be included in this list.

tree: Option<Tree>

Rarely updated information about the tree as a whole. This may be omitted if it has not changed since the previous update, but providing the same information again is also allowed. This is required when initializing a tree.

focus: Option<NodeId>

The node with keyboard focus within this tree, if any. The most recent focus, if any,must be provided with every tree update.

This field must contain a value if and only if the native host (e.g. window) currently has the keyboard focus. This implies that the AccessKit provider must track the native focus state and send matching tree updates. Rationale: A robust GUI toolkit must do this native focus tracking anyway in order to correctly render widgets (e.g. to draw or not draw a focus rectangle), so this focus tracking should not be duplicated between the toolkit and the AccessKit platform adapters.

Trait Implementations

impl Clone for TreeUpdate

fn clone(&self) -> TreeUpdate

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TreeUpdate

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TreeUpdate

fn default() -> TreeUpdate

Returns the “default value” for a type.

impl<T: FnOnce() -> TreeUpdate> From<T> for TreeUpdate

fn from(factory: T) -> Self

Converts to this type from the input type.

impl PartialEq<TreeUpdate> for TreeUpdate

fn eq(&self, other: &TreeUpdate) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for TreeUpdate