Struct ScrollState 

pub struct ScrollState {
    pub selected_idx: Option<usize>,
    pub scroll_top: usize,
}

Generic scroll/selection state for a vertical list menu.

Encapsulates the common behavior of a selectable list that supports:

• Optional selection (None when list is empty)
• Wrap-around navigation on Up/Down
• Maintaining a scroll window (scroll_top) so the selected row stays visible

Callers own the filtered row count and the visible window size. Every mutation method takes those values instead of caching them here, so list views can apply filters, pagination, or density changes without this helper knowing about their data model. Passing a stale length after filtering would leave selection pointing at the wrong row, so callers should clamp or move through this type immediately after changing their visible row set.

Fields

selected_idx: Option<usize>

scroll_top: usize

Implementations

impl ScrollState

pub fn new() -> Self

pub fn reset(&mut self)

Reset selection and scroll.

pub fn clamp_selection(&mut self, len: usize)

Clamp selection to be within the [0, len-1] range, or None when empty.

pub fn move_up_wrap(&mut self, len: usize)

Move selection up by one, wrapping to the bottom when necessary.

pub fn move_down_wrap(&mut self, len: usize)

Move selection down by one, wrapping to the top when necessary.

pub fn page_up_clamped(&mut self, len: usize, visible_rows: usize)

Move selection up by one visible page, clamping at the first row.

Page movement intentionally does not wrap. It mirrors terminal list behavior where repeated page-up/page-down converges at the nearest edge while still keeping the selected row visible.

pub fn page_down_clamped(&mut self, len: usize, visible_rows: usize)

Move selection down by one visible page, clamping at the last row.

Page movement intentionally does not wrap. It mirrors terminal list behavior where repeated page-up/page-down converges at the nearest edge while still keeping the selected row visible.

pub fn jump_top(&mut self, len: usize, visible_rows: usize)

Jump selection to the first row.

pub fn jump_bottom(&mut self, len: usize, visible_rows: usize)

Jump selection to the last row.

pub fn ensure_visible(&mut self, len: usize, visible_rows: usize)

Adjust scroll_top so that the current selected_idx is visible within the window of visible_rows.

Trait Implementations

impl Clone for ScrollState

fn clone(&self) -> ScrollState

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ScrollState

impl Debug for ScrollState

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

Formats the value using the given formatter.

impl Default for ScrollState

fn default() -> ScrollState

Returns the “default value” for a type.