Struct ScrollbarState 

pub struct ScrollbarState {
    pub total_items: usize,
    pub visible_items: usize,
    pub scroll_offset: usize,
}

State needed to render and interact with a scrollbar

Fields

total_items: usize

Total number of items/lines

visible_items: usize

Number of items visible in the viewport

scroll_offset: usize

Current scroll offset (first visible item index)

Implementations

impl ScrollbarState

pub fn new( total_items: usize, visible_items: usize, scroll_offset: usize, ) -> Self

Create a new scrollbar state

pub fn thumb_geometry(&self, track_height: usize) -> (usize, usize)

Calculate thumb position and size for a given track height

Returns (thumb_start, thumb_size) in rows

pub fn click_to_offset(&self, track_height: usize, click_row: usize) -> usize

Convert a click position on the track to a scroll offset

Arguments

• track_height - Height of the scrollbar track in rows
• click_row - Row within the track that was clicked (0-indexed)

Returns

The scroll offset that would position the thumb at the click location

pub fn is_thumb_row(&self, track_height: usize, row: usize) -> bool

Check if a row is within the thumb area

pub fn offset_for_thumb_top( &self, track_height: usize, target_thumb_top: usize, ) -> usize

Inverse of [thumb_geometry]: compute the scroll offset that places the thumb’s top at (or as close as possible to) target_thumb_top. Use this — not click_to_offset — when a caller needs the thumb to land at a specific row on the track (e.g. press on the track to recentre the thumb under the cursor): click_to_offset divides by track_height rather than the actual max_thumb_top, so its result drifts above the intended row by a factor of thumb_size / track_height.

pub fn drag_to_offset( &self, track_height: usize, drag_start_row: usize, drag_start_offset: usize, current_row: usize, ) -> usize

Compute the scroll offset for a drag that preserves the cursor’s position within the thumb.

When the user presses on the thumb itself, the thumb shouldn’t jump so its top aligns with the cursor — the cursor should stay pinned to the same spot on the thumb. Callers capture the press position (drag_start_row) and the scroll offset at that moment (drag_start_offset), then call this on every subsequent drag event.

Arguments

• track_height — height of the scrollbar track in rows
• drag_start_row — track-relative row where the drag started
• drag_start_offset — scroll offset at the time of the press
• current_row — track-relative row of the cursor now

Trait Implementations

impl Clone for ScrollbarState

fn clone(&self) -> ScrollbarState

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ScrollbarState

impl Debug for ScrollbarState

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

Formats the value using the given formatter.