Spacing

The spacing job prepares sampled spacing suggestions from a saved font using the external native worker. It changes existing foreground positions and widths through generic patches after you review and apply the result.

Prepare a proposal

Use start_job with kind="spacing", a document ID and an optional glyphs list. Omit delta. Omitted glyph names select all master layers; special layers are outside this workflow.

{
  "document_id": "<document ID>",
  "kind": "spacing",
  "glyphs": ["H", "O", "n", "o"],
  "options": {"reference": "auto", "widthMode": "auto"}
}

Option	Default and use
reference	auto: choose a class-aware reference. * means self-reference; a glyph name selects it explicitly.
references	Per-glyph reference overrides. Explicit references do not silently fall back.
masters	Selected master IDs; omitted or empty means all masters.
widthMode	auto, preserve or proportional.
area	400; controls the sampled spacing area.
depth	15 percent of x-height.
sampleStep	5 font units.

Automatic selection uses H for uppercase, x/n/o for lowercase and one/zero for decimal figures, with reported fallbacks. These are sampled suggestions, not a guarantee of optimal optical spacing.

Review the evidence

Call get_job and inspect the report sample and full report.json path. Review references, fallback choices, before/after metrics, preservation reasons and unavailable targets before applying.

The workflow preserves tabular widths, zero-width marks, metrics keys and native component alignment. preserve keeps widths explicitly. proportional disables automatic equal-figure detection; named tabular glyphs and fixed-pitch widths remain protected. Alignment-dependent layers can be excluded rather than overridden.

Tiny differences

The absolute tolerance is 0.001 font units, inclusive. A translation of 0.0009 or 0.001 units is skipped; a translation of 0.0011 remains significant. Width is evaluated independently: a negligible shift can accompany a meaningful width patch. Reports describe the effective changes after this filtering.

This is a project comparison policy, not a universal minimum coordinate supported by Glyphs. A meaningful requested translation that a native setter cannot store exactly is reported as unavailable during preparation. Do not round it merely to make the test pass. Native apply, Undo/Redo and rollback remain exact.

Apply and inspect

Use apply_job, wait for completion with get_job, then review varied text in Glyphs. Enable Changes Against Reference to inspect the active layer's geometry and width. It does not evaluate spacing quality for you.

Use bounded read_entities for exact widths and outline hashes. Native displayed bearings can be rounded; coordinate or detached native measurements supply fractional evidence. To abandon the result use discard_job; when persistence is authorized, use accept_job to verify it and save the whole document.