By name: pbir-layout-engine description: "Deterministic layout-arithmetic linter for dashboard/report page definitions. Runs seven checks — no-overlap (AABB), within-canvas, equal-gap, column-alignment, and three PBIR-specific invariants (no-empty-binding, bounded theme-override count, visualType/displayOption schema validity) — against a page JSON, a page directory, or a fixture set. Stdlib-only, no network, exit-coded for CI. The load-bearing technical core under the data-viz-designer agent; usable standalone to lint a Power BI PBIR page layout."
Skill: pbir-layout-engine
What this is
A runnable, deterministic linter — lint.py — that checks a dashboard/report page's visuals against hard layout arithmetic plus, for Power BI PBIR Enhanced inputs, three PBIR-specific invariants. It is the load-bearing, testable core beneath the data-viz-designer agent (Phase 1 of docs/research/2026-06-02-data-viz-agent/build-plan.md), and it stands alone: a Power BI author can lint a page's layout without invoking the agent.
It is not a style opinion engine — it checks arithmetic facts (do boxes overlap? do they fit the canvas? are gaps equal? are columns aligned?) and schema facts (is the visualType in the canon enum?), each with a precise fix_hint.
The seven checks
| Check | Name | Applies to | Default severity |
|---|---|---|---|
check-1 |
No-overlap (AABB bounding-box) | all stacks | error |
check-2 |
Within-canvas | all stacks | error |
check-3 |
Equal-gap (horizontal) | all stacks | warning |
check-4 |
Column-alignment (vertical) | all stacks | warning |
check-5 |
No-empty-binding (queryState projections present) |
PBIR only | error |
check-6 |
Theme-compliance (bounded override count) | PBIR only | warning |
check-7 |
Schema-valid (visualType / displayOption enums) |
PBIR only | error |
PBIR checks (5–7) auto-enable when the input carries a $schema; force with --pbir / disable with --no-pbir.
CLI contract
python3 plugins/ravenclaude-core/skills/pbir-layout-engine/lint.py [OPTIONS] <input-path>
<input-path> is a single page JSON, a page directory, or a fixture directory. It MUST NOT contain .. and MUST resolve inside the repo root (else exit 2 — the purity-contract failure).
| Option | Effect |
|---|---|
--pbir / --no-pbir |
force PBIR checks on/off (default: auto-detect from $schema) |
--format text|json |
output format (default text); the JSON envelope is {schema_version, linter_version, input_path, exit_code, summary, findings[]} |
--strict |
exit non-zero on any finding ≥ warning (default: only error findings set a non-zero exit) |
--tolerance-gap=PX / --tolerance-align=PX |
override check-3/4 tolerances (a per-page _lintConfig wins) |
--list-checks / --version |
print the checks / pinned schema version and exit |
Exit codes: 0 pass (or only info-level) · 1 error finding (or warning under --strict) · 2 I/O, parse, or path-rejection (purity failure) · 3 visualType enum could not be parsed from the canon file (see below).
Suppression — _lintConfig and _lintIgnore
A page may carry a _lintConfig.tolerance block (equal_gap_px, column_align_px) to widen check-3/4 for a deliberately hand-tuned grid; a visual may carry _lintIgnore: ["check-3"] to opt out of a specific check. The hand-tuned-vertical-grid-passes fixture exercises this path.
The one sanctioned cross-plugin read
check-7 validates visualType against the canon enum in plugins/power-platform/knowledge/pbir-enhanced-reference.md § 1 — parsed at runtime, never duplicated here, so the enum and the linter cannot silently drift. This is the linter's only cross-plugin filesystem dependency (documented in the module docstring). If § 1 can't be located or parsed, check-7 cannot run and the process exits 3 rather than passing silently.
Output Contract
The linter's machine output is the --format json envelope above (snake_case keys, null over key-omission, exit_code mirroring the process exit). When a reviewer critiques a linter integration in a PR, the response ends with the cross-plugin Structured Output JSON block per structured-output/SKILL.md.
Proven by Gate 92
scripts/audit-gates.sh Gate 92 + the 12 fixtures under tests/fixtures/data-viz/ are the bidirectional floor: each bad-page-* fixture fires exactly its targeted check (non-zero exit), and good-page + hand-tuned-vertical-grid-passes exit 0. Checks 3/4/6 are warning severity, so their bad fixtures are asserted under --strict. Companion reference: knowledge/pbir-design-lint.md.
Scope boundary
This skill is the linter only. The chart-selection / WCAG-contrast / IBCS-variance skills, the data-viz-designer agent that orchestrates them, and the visual-design knowledge files are separate deliverables of the same build plan (Phases 3–6) and ship independently.