Module justification 

Microtypographic justification controls for the Knuth-Plass pipeline.

This module provides stretch/shrink/spacing penalty configuration that modulates how the line-break optimizer distributes white space across justified text. It complements super::vertical_metrics (vertical spacing) with horizontal spacing controls.

Design

All widths are in cell columns (terminal-native units). The stretch and shrink values define the allowable range of space adjustment per space category. The optimizer penalizes deviations from the natural width according to a cubic badness function (TeX convention).

TeX heritage

The glue model follows TeX’s concept: each space has a natural width, a stretchability, and a shrinkability. The adjustment ratio r is computed as slack / (total_stretch or total_shrink), and badness is |r|³ × scale.

Structs

GlueSpec

TeX-style glue specification: natural width + stretch + shrink.

JustificationControl

Unified justification configuration.

SpacePenalty

Penalty modifiers for space adjustment quality.

Enums

JustifyMode

Text alignment mode.

SpaceCategory

Classification of horizontal space types.

Constants

SUBCELL_SCALE

Sub-cell units per cell column.