Struct HeaderLayout 

pub struct HeaderLayout<'a> { /* private fields */ }

A collapsed block fold’s one-line display layout: the (inline-fold- aware) header text, the … placeholder gap, then the fold’s real closing tail — fn main() { … }. The single source for the placeholder render, caret placement on the tail, selection washes, hit-testing, the hover-chip rect, and the preview anchor, so they agree to the pixel by construction.

Implementations

impl<'a> HeaderLayout<'a>

pub fn head(&self) -> &RowLayout<'a>

The header row’s projection (for hits resolving to HeaderHit::Head).

pub fn head_cells(&self) -> u32

Rendered display width of the header text — where the placeholder gap begins. Inline-fold aware: a collapsed inline fold before the block’s opener shrinks it.

pub fn gap_center(&self) -> f32

The fractional cell at the center of the … gap, where the chip and its … glyph both center.

pub fn tail_cell(&self) -> u32

The display cell where the inline closing tail begins.

pub fn last_row(&self) -> BufferRow

The fold’s last buffer row (the tail’s real home).

pub fn tail_start_col(&self) -> u32

Byte column on the last row where the visible tail starts.

pub fn tail_col_cell(&self, col: u32) -> Option<u32>

Byte column on the last row → display cell on the header row, using full-line tab stops (the caret/hit/selection convention). None for a column in the leading whitespace before the visible tail.

pub fn tail_cells(&self) -> u32

The tail’s rendered width in cells.

pub fn width(&self) -> u32

The collapsed line’s total rendered width (head + gap + tail), in cells.

pub fn tail_glyphs(&self) -> impl Iterator<Item = TailGlyph> + '_

The visible tail glyphs at their header-row display cells.

pub fn hit(&self, cell: f32, bias: Bias) -> HeaderHit

Resolve a (fractional) display cell on the collapsed header line to the region it falls in, with the ±half-cell boundaries the hit-test has always used: at/after the tail (minus half a cell) → the tail column; past the header text (plus half a cell) → the gap; else the head.