Struct HeightIndex 

pub struct HeightIndex { /* private fields */ }

Chunked prefix-sum index over row heights.

Implementations

impl HeightIndex

pub fn new() -> HeightIndex

pub fn len(&self) -> usize

Number of rows.

pub fn is_empty(&self) -> bool

pub fn total_height(&mut self) -> u64

Total height of every row, in pixels.

pub fn height_at(&self, row: usize) -> u32

Height of one row.

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

Whether row row’s height came from a real layout pass.

pub fn unmeasured_count(&self) -> usize

How many rows still carry an estimated height.

The view uses this to decide whether an idle-time measure backfill is worth scheduling.

pub fn push_back(&mut self, height: u32, measured: bool)

Append a row.

pub fn push_front(&mut self, height: u32, measured: bool)

Prepend a row — the chat-history backfill path.

pub fn insert(&mut self, row: usize, height: u32, measured: bool)

Insert at an arbitrary row position.

Used by the Load-Older path, which inserts before a saved divider that is generally not at the front (server notices precede it, live messages follow it). O(chunk length) rather than O(n): only the containing chunk shifts, and the chunk prefixes past it are marked stale rather than recomputed.

pub fn remove(&mut self, row: usize) -> Option<u32>

Remove a row, returning its height.

pub fn drain_front(&mut self, n: usize)

Drop the first n rows — the scrollback trim.

pub fn set_height(&mut self, row: usize, height: u32, measured: bool)

Replace a row’s height, e.g. when a real layout pass supersedes an estimate or an image texture finally lands.

pub fn invalidate_all_measurements(&mut self)

Mark every row unmeasured, keeping the current heights as estimates.

This is a width or font change. Note what it does not do: re-measure anything. The old heights stay as the estimate so the scrollbar remains plausible, and rows are re-laid-out lazily as they become visible. That is the whole reason resize is O(visible) here and O(scrollback) in xtext.

pub fn offset_of(&mut self, row: usize) -> u64

Pixel offset of the top of row row.

pub fn locate(&mut self, y: u64) -> Option<Hit>

Which row contains pixel offset y, and how far into it.

y past the end clamps to the last row’s bottom edge, so a caller that over-scrolls gets a sane answer rather than None.

Trait Implementations

impl Debug for HeightIndex

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

Formats the value using the given formatter.

impl Default for HeightIndex

fn default() -> Self

Returns the “default value” for a type.