Struct SemanticsRequester 

pub struct SemanticsRequester { /* private fields */ }

A handle an app holds to say that what its semantics recorder would report has changed.

A .semantics() recorder is re-run on every collection, so it always reports the app’s current answer. It cannot say when that answer changed, and a tree is only re-collected when some node marks its semantics dirty — which until now meant attaching a node, rebuilding its modifier chain, or a layout pass. A screen that is one Canvas does none of those: its layout never changes and its frame loop draws rather than recomposes, so the tree it published at boot was the tree a screen reader kept reading.

This is the way out, and it is Jetpack Compose’s: SemanticsModifierNode.invalidateSemantics(). Remember one requester, hang it on the same node as the recorder, and call invalidate when the content changes — no recomposition, no layout pass.

let semantics = remember(SemanticsRequester::new).with(Clone::clone);
// ... in the composition:
Modifier::empty()
    .semantics_requester(&semantics)
    .semantics(move |config| { /* reads live app state */ })
// ... and in the frame loop, guarded by a revision so an unchanged tree is
// not republished every frame:
if revision != last_revision {
    last_revision = revision;
    semantics.invalidate();
}

Implementations

impl SemanticsRequester

pub fn new() -> Self

pub fn invalidate(&self)

Marks the attached node’s semantics for re-collection on the next frame.

Idempotent within a frame and cheap: the node joins a set the shell drains once per frame. Before the node attaches, and after it detaches, this does nothing — there is no tree to mark.

pub fn node_id(&self) -> Option<NodeId>

The layout node this requester is bound to, if it is attached.

Trait Implementations

impl Clone for SemanticsRequester

fn clone(&self) -> SemanticsRequester

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SemanticsRequester

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

Formats the value using the given formatter.

impl Default for SemanticsRequester

fn default() -> SemanticsRequester

Returns the “default value” for a type.