Struct RowHeights 

pub struct RowHeights { /* private fields */ }

The heights a list slices by: a measured number per row where one is known, an estimate everywhere else, and the prefix sums over both.

The app owns it and hands the same one back every frame — a widget composed from primitives keeps no state of its own, which is what keeps it reachable from a scripting frontend. Rebuild it (or Self::clear) when the rows themselves change.

Implementations

impl RowHeights

pub fn new(rows: usize, estimate: f32) -> RowHeights

rows rows, none measured, each standing at estimate logical px until it is. The estimate only has to be the right order of magnitude: it decides how wrong the scrollbar is before the list has been scrolled through, and nothing else.

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn set_len(&mut self, rows: usize)

Grows or shrinks to rows, keeping what is still in range — rows appended to a log keep every height already measured, and cost nothing until something asks about them. A list whose rows changed rather than grew wants Self::clear.

pub fn clear(&mut self)

Forgets every measurement, keeping the length and the seed — the call for a list whose contents changed under the same indices.

pub fn set(&mut self, i: usize, h: f32)

Records row i’s height. Rows measured this way are what the estimate for the others is the mean of.

pub fn measured(&self, i: usize) -> Option<f32>

Row i’s height as it was measured, or None for one standing at the estimate.

pub fn get(&self, i: usize) -> f32

Row i’s height: measured, or the estimate.

pub fn estimate(&self) -> f32

What an unmeasured row stands at: the mean of the measured ones, or the caller’s seed before there are any.

pub fn width(&self) -> f32

The width the measurements were taken at, or NaN before any.

pub fn set_width(&mut self, w: f32) -> bool

Declares the content width the next measurements are for. A width that differs from the cached one drops every height — the rows wrap differently now — and returns true. list calls this from the container’s own laid-out box.

pub fn offset_of(&mut self, i: usize) -> f32

The top of row i in content coordinates — the height of everything above it. offset_of(len()) is the whole list’s height.

pub fn total(&self) -> f32

The list’s total height, measured and estimated together — what the two spacers and the scrollbar are made of. Kept as it goes, so the tail spacer costs nothing however long the list is.

pub fn row_at(&mut self, y: f32) -> usize

The row y (content coordinates) lands in: the last row whose top is at or above it, clamped to the list. The binary search that replaces y / row_h.

impl RowHeights

pub fn slice(&mut self, reading: ListReading) -> ListSlice

Starts a frame’s slicing from reading: the content width (a new one drops every height, since the rows rewrap), the anchors, and the first range.

Trait Implementations

impl Clone for RowHeights

fn clone(&self) -> RowHeights

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RowHeights

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

Formats the value using the given formatter.