Enum WidgetInstanceState 

pub enum WidgetInstanceState {
    None,
    List {
        scroll_offset: u32,
        selected_index: i32,
    },
    Text {
        value: String,
        cursor_byte: u32,
        scroll: u32,
    },
    Tree {
        scroll_offset: u32,
        selected_index: i32,
        expanded_keys: HashSet<String>,
    },
}

Widget instance state retained across spec updates, keyed by the widget’s stable key. This is the “Spec/instance separation” described in §6 of the design doc — a plugin can rebuild its WidgetSpec from scratch on every model change without losing scroll offset, cursor position, expanded keys, or focus, because stateful widgets look up their instance state by key.

Variants

None

Empty/placeholder — never persisted, used as a default.

List

List instance state: host-owned scroll offset and selected index. selected_index becomes authoritative after first render — same correctness reasoning as TextInput’s host-owned value (host can mutate it via WidgetCommand::SelectMove without racing the plugin’s spec round-trip).

Fields

scroll_offset: u32

selected_index: i32

Text

Text instance state: host-owned value + cursor byte offset, plus a viewport scroll offset that’s only meaningful for multi-line (rows > 1) variants — the row index of the first visible line. Single-line text widgets always render from value byte 0 and rely on render-time head-truncate scrolling, so they leave scroll at 0.

Becomes authoritative once the widget mounts; the spec’s value / cursor_byte are initial-only (used at first render and ignored thereafter). This guarantees correctness under concurrent keystrokes — the plugin’s spec round-trip can’t race against multiple in-flight WidgetCommand mutations because the host doesn’t read from the spec for value at all once instance state exists.

Fields

value: String

cursor_byte: u32

scroll: u32

Tree

Tree instance state: host-owned scroll offset, selected index, and the set of expanded item keys. All three become authoritative after first render — the spec’s selected_index / expanded_keys are seed values only. expanded_keys is a HashSet because expansion is set-membership semantically (a key is either expanded or not); ordering doesn’t matter and we hit-test on contains.

Fields

scroll_offset: u32

selected_index: i32

expanded_keys: HashSet<String>

Trait Implementations

impl Clone for WidgetInstanceState

fn clone(&self) -> WidgetInstanceState

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for WidgetInstanceState

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

Formats the value using the given formatter.

impl Default for WidgetInstanceState

fn default() -> WidgetInstanceState

Returns the “default value” for a type.