constraint-layout

name	constraint-layout
description	Use when implementing or testing TaTUÍ's layout engine: Constraint, Rect splitting, the solver, spacing/margins, or the layout cache. Covers constraint semantics, integer rounding, and cache keying. Triggers: layout, constraint, split, rect, flex, percentage, ratio, fill, solver.

Constraint-based layout

Constraint kinds (ADR-0004)

Length(n), Percentage(p), Ratio(num, den), Min(n), Max(n), Fill(weight).

Semantics

• A layout splits a Rect along a Direction (Horizontal/Vertical) into segments.
• Fixed intents (Length, Percentage, Ratio) are honored first; Min/Max clamp; Fill distributes leftover space proportional to weight.
• All arithmetic is on integer cells. Distribute rounding remainder deterministically (left-to-right / top-to-bottom) so totals equal the parent extent — no lost or overlapping cells.

Solver strategy

• v1: greedy solver behind the final Constraint API.
• Later: linear (kasuari-style) solver, swappable without changing callers.

Caching

• Solving repeats every frame; cache solved results in a thread-local LRU keyed by (area, direction, constraints, spacing, margin).

Testing

Table-driven truth-tables: (area, direction, constraints) -> expected rects. Cover Min/Max/Ratio/ Fill interactions and rounding edges.