Struct CanvasSemanticsNode 

pub struct CanvasSemanticsNode {
    pub key: u64,
    pub bounds: Rect,
    pub label: String,
    pub role: Option<SemanticsWidgetRole>,
    pub state_description: Option<String>,
    pub on_click_label: Option<String>,
    pub clickable: bool,
    pub selected: Option<bool>,
    pub toggled: Option<ToggleableState>,
    pub enabled: bool,
    pub custom_actions: Vec<SemanticsCustomAction>,
}

A semantics node for content that is drawn rather than laid out.

An immediate-mode surface — one Canvas that paints a whole screen — has exactly one layout node, so the semantics tree built from layout has exactly one node to offer a screen reader. This is the escape hatch: the drawing code already knows where it put every control, so it publishes those rectangles as semantics directly. Android’s own answer for a canvas-drawn View is the same shape (ExploreByTouchHelper feeding virtual view ids into an AccessibilityNodeProvider), and Cranpose’s Android bridge is already an AccessibilityNodeProvider, so these land as first-class virtual views next to the ones layout produces.

bounds is in the publishing node’s own coordinates (logical px, origin at that node’s top-left), because that is what a draw scope works in.

Fields

key: u64

Identity that must survive a redraw.

A screen reader parks its cursor on a virtual view id; if the id for “the Haptics switch” changes when the list scrolls, the cursor jumps. Derive this from what the control is (a row index, an enum discriminant), never from where it currently sits.

bounds: Rect

Where the control was drawn, relative to the publishing node.

label: String

What the screen reader reads for the control.

role: Option<SemanticsWidgetRole>

What kind of control it is, as the screen reader announces it.

state_description: Option<String>

Compose’s stateDescription — what the control currently reads as (“CAMPAIGN”, “3 of 18 gold”), spoken after the label and re-spoken on its own when only the state changed.

on_click_label: Option<String>

Compose’s onClick(label = …). TalkBack reads it as “double tap to <label>”, so it is a verb phrase, not a repeat of the label.

clickable: bool

Whether the control can be activated.

selected: Option<bool>

Compose’s selected, for Role.RadioButton/Role.Tab.

toggled: Option<ToggleableState>

Compose’s toggleableState, for Role.Switch/Role.Checkbox.

enabled: bool

Whether the control accepts input. A disabled control is announced as such.

custom_actions: Vec<SemanticsCustomAction>

Named actions that the screen reader lists in its actions menu for the control.

Implementations

impl CanvasSemanticsNode

pub fn control(key: u64, bounds: Rect, label: impl Into<String>) -> Self

A clickable control drawn at bounds.

pub fn text(key: u64, bounds: Rect, label: impl Into<String>) -> Self

A drawn label that is read but not activated.

pub fn with_role(self, role: SemanticsWidgetRole) -> Self

Returns the node with role set.

pub fn with_state_description(self, state: impl Into<String>) -> Self

Returns the node with the state description state set. Compose’s stateDescription.

pub fn with_click_label(self, label: impl Into<String>) -> Self

Returns the node with label set as the verb phrase for activation. The node becomes clickable.

pub fn with_selected(self, selected: bool) -> Self

Returns the node with its selected state set to selected.

pub fn with_toggled(self, toggled: impl Into<ToggleableState>) -> Self

Returns the node with its toggle state set to toggled. A bool converts to On or Off.

pub fn with_enabled(self, enabled: bool) -> Self

Returns the node with enabled set. A disabled node is announced as such.

pub fn with_custom_action(self, action: SemanticsCustomAction) -> Self

Returns the node with action added to its custom actions.

Trait Implementations

impl Clone for CanvasSemanticsNode

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CanvasSemanticsNode

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

Formats the value using the given formatter.

impl Default for CanvasSemanticsNode

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for CanvasSemanticsNode

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for CanvasSemanticsNode