Feat/zpl jm density

README.md

@@ -86,7 +86,7 @@ Edit an imported label and export it again:
 
 - **Preserved:** everything you didn't touch comes back byte-for-byte, including fields, label settings, comments, whitespace, and commands the editor doesn't model. A zero-edit import/export cycle reproduces the file exactly.
 - **Regenerated:** only the objects you edit, add, or delete are re-emitted from the model. The rest of the file is spliced back unchanged.
-- **Full-regeneration fallback:** a few constructs make per-object patching unsafe: `^MU` unit scaling, non-default `^CC`/`^CT`/`^CD` command prefixes, non-UTF-8 `^CI` encoding, non-default `^FE` embed delimiters, a bare `^FN` declared outside a field, and a barcode relying on a `^BY` from an earlier field. On such labels the first edit regenerates the whole label; with no edits the export stays byte-for-byte.
+- **Full-regeneration fallback:** a few constructs make per-object patching unsafe: `^MU` unit scaling, non-default `^CC`/`^CT`/`^CD` command prefixes, non-UTF-8 `^CI` encoding, non-default `^FE` embed delimiters, a bare `^FN` declared outside a field, an in-span `^JM` density switch, and a barcode relying on a `^BY` from an earlier field. On such labels the first edit regenerates the whole label; with no edits the export stays byte-for-byte.
 
 Byte capture at import is deliberately conservative: when a field can't be mapped cleanly to a single object, the whole label falls back to model regeneration, which keeps the content but not the exact bytes. The captured bytes are stored in saved `.json` designs; a design from an older app version with an outdated capture format is detected and rebuilt.
 
@@ -152,7 +152,7 @@ Both `.zpl` and `.json` round-trip cleanly. `.zpl` preserves all printable conte
 ## Coverage
 
 <!-- coverage:start (generated from docs/zpl-roadmap.md by scripts/gen-coverage.mjs; run `pnpm coverage:gen`) -->
-113 of the 225 ZPL II commands tracked in the [roadmap](docs/zpl-roadmap.md) are supported today. Categorical breakdown:
+114 of the 225 ZPL II commands tracked in the [roadmap](docs/zpl-roadmap.md) are supported today. Categorical breakdown:
 
 | Area | Supported |
 |---|---|
@@ -169,7 +169,7 @@ Both `.zpl` and `.json` round-trip cleanly. `.zpl` preserves all printable conte
 | Text & fonts | 7 / 14 |
 | Print quality | 10 / 18 |
 | Configuration & persistence | 3 / 5 |
-| Hardware / Host comm / RFID / Network | 0 / 87 |
+| Hardware / Host comm / RFID / Network | 1 / 87 |
 <!-- coverage:end -->
 
 ---

docs/zpl-roadmap.md

@@ -249,7 +249,7 @@ These need printer-side feedback or are intrinsically connection bound.
 | `[ ]` | `^JJ` | set auxiliary port | `Native build` |
 | `[ ]` | `^JS` | sensor select (reflective / transmissive) | `Native build` |
 | `[ ]` | `~JL` | set label length | `Native build` |
-| `[ ]` | `^JM` | set dots per millimeter (B halves density and doubles format scale; A = normal, default) | `Coming soon` |
+| `[x]` | `^JM` | set dots per millimeter (B halves density and doubles format scale; A = normal, default) | |
 | `[ ]` | `~JN` | head test fatal | `Native build` |
 | `[ ]` | `~JO` | head test non-fatal | `Native build` |
 | `[ ]` | `~JP` | pause and cancel format | `Native build` |

packages/core/src/lib/barcodeScannability.ts

@@ -1,4 +1,5 @@
 import type { PreflightCtx, PreflightProducerResult } from "../types/preflight";
+import { effectiveDpmm } from "../types/LabelConfig";
 import { mmToUnitExact, unitLabel, type Unit } from "./units";
 
 /** Recommended minimum barcode module / X-dimension in mm for reliable general
@@ -34,7 +35,7 @@ export function moduleTooSmallFindings(
 export function moduleTooSmallPreflight<P extends object>(
   prop: keyof P & string,
 ): (obj: { props: P }, ctx: PreflightCtx) => PreflightProducerResult[] {
-  return (obj, ctx) => moduleTooSmallFindings(obj.props[prop] as number, ctx.label.dpmm, ctx.unit);
+  return (obj, ctx) => moduleTooSmallFindings(obj.props[prop] as number, effectiveDpmm(ctx.label), ctx.unit);
 }
 
 /** Registry `preflight` for legacy/niche symbologies (Code 49, TLC39): the
@@ -44,7 +45,7 @@ export function limitedSupportPreflight<P extends object>(
   prop: keyof P & string,
 ): (obj: { props: P }, ctx: PreflightCtx) => PreflightProducerResult[] {
   return (obj, ctx) => [
-    ...moduleTooSmallFindings(obj.props[prop] as number, ctx.label.dpmm, ctx.unit),
+    ...moduleTooSmallFindings(obj.props[prop] as number, effectiveDpmm(ctx.label), ctx.unit),
     { kind: "printerSupportLimited" },
   ];
 }

packages/core/src/lib/designFile.ts

@@ -1,5 +1,5 @@
 import { z } from "zod";
-import { labelConfigSchema, type LabelConfig } from "../types/LabelConfig";
+import { JM_DENSITY_VALUES, labelConfigSchema, type JmDensity, type LabelConfig } from "../types/LabelConfig";
 import { labelObjectBaseSchema } from "../types/LabelObject";
 import {
   variableSchema,
@@ -9,7 +9,8 @@ import {
 } from "../types/Variable";
 import { dbSourceRefSchema, type DbSourceRef } from "../types/DataSource";
 import type { LabelObject } from "../types/Group";
-import { blockOverlaySchema, type BlockOverlay } from "./zplOverlay/overlay";
+import { blockOverlaySchema, overlayText, type BlockOverlay } from "./zplOverlay/overlay";
+import { reconstructLegacyBlockHeads } from "./zplHeadScan";
 import { visitLeavesInPages, foldSerialLeaf, bindSingleMarkerLeaf, sanitiseVariableNames, safeUniqueNameById } from "./objectTree";
 import { insertReverseBackingBoxes, pageNeedsReverseBacking } from "./reverseBacking";
 import { ok, err, type Result } from "./result";
@@ -19,10 +20,10 @@ import { ok, err, type Result } from "./result";
  *  migrator below and dispatch on `schemaVersion` in `parseDesignFile`.
  *  The persist middleware in `labelStore` has its own independent
  *  version for localStorage state; do not conflate. */
-export const CURRENT_DESIGN_SCHEMA_VERSION = 3;
+export const CURRENT_DESIGN_SCHEMA_VERSION = 4;
 
 export type DesignFileError = "parse_error" | "invalid_schema";
-export interface DesignFilePage { objects: LabelObject[]; overlay?: BlockOverlay }
+export interface DesignFilePage { objects: LabelObject[]; overlay?: BlockOverlay; jmDensity?: JmDensity }
 export interface DesignFile {
   label: LabelConfig;
   pages: DesignFilePage[];
@@ -64,10 +65,13 @@ const labelObjectSchema: z.ZodType<unknown> = z.union([groupSchema, leafSchema])
 const pageSchema = z.object({
   objects: z.array(labelObjectSchema),
   overlay: blockOverlaySchema.optional().catch(undefined),
+  jmDensity: z.enum(JM_DENSITY_VALUES).optional(),
 });
 
 const designFileSchema = z.object({
-  schemaVersion: z.literal(3),
+  // v3 predates ^JM: it loads through the legacy JM reconstruction. v4 carries
+  // the persisted density fields; both are read, anything else is rejected.
+  schemaVersion: z.union([z.literal(3), z.literal(4)]),
   label: labelConfigSchema,
   pages: z.array(pageSchema),
   variables: z.array(variableSchema).optional(),
@@ -93,6 +97,7 @@ export function parseDesignFile(text: string): Result<DesignFile, DesignFileErro
   const parsed = designFileSchema.safeParse(json);
   if (parsed.success) {
     const pages = parsed.data.pages as unknown as DesignFilePage[];
+    reconstructLegacyJmDensity(parsed.data.label, pages);
     const variables = parsed.data.variables ?? [];
     // Enforce the marker-safe name invariant: an old/foreign name like `clock:Y`
     // can't be a single-bind marker, so rename offenders + rewrite their markers.
@@ -187,6 +192,31 @@ function migrateSingleBindToMarker(json: unknown): void {
   j.schemaVersion = 3;
 }
 
+/** Payloads without ^JM modeling carried a head ^JM only in the raw overlay
+ *  bytes, which a full regen would drop. Reconstructs the fold a fresh import
+ *  would yield; no-op once any label/page density or recorded head is present. */
+export function reconstructLegacyJmDensity(
+  label: { jmDensity?: JmDensity },
+  pages: DesignFilePage[],
+): void {
+  if (label.jmDensity !== undefined) return;
+  for (const page of pages) {
+    if (page.jmDensity !== undefined || page.overlay?.head) return;
+  }
+  const heads = reconstructLegacyBlockHeads(
+    pages.map((page) => (page.overlay ? overlayText(page.overlay) : undefined)),
+  );
+  const anchorIndex = pages.findIndex((p) => p.objects.length > 0);
+  if (anchorIndex >= 0) label.jmDensity = heads[anchorIndex]?.density;
+  const designJm: JmDensity = label.jmDensity ?? "A";
+  pages.forEach((page, i) => {
+    const { density, head } = heads[i] ?? {};
+    const blockJm: JmDensity = density ?? "A";
+    if (blockJm !== designJm) page.jmDensity = blockJm;
+    if (head && page.overlay) page.overlay.head = head;
+  });
+}
+
 interface SerializedDesign {
   schemaVersion: number;
   label: LabelConfig;

packages/core/src/lib/objectBounds.ts

@@ -15,6 +15,7 @@ import { getAllLeaves, isGroup } from "../types/Group";
 import type { LeafObject } from "../registry";
 import { BARCODE_1D_TYPES, STACKED_2D_TYPES, getEntry } from "../registry";
 import type { LabelConfig } from "../types/LabelConfig";
+import { effectiveDpmm, type JmDensity } from "../types/LabelConfig";
 import { isAxisSwapped, objectRotation, type ZplRotation } from "../registry/rotation";
 import { resolveTextMode } from "../registry/text";
 import { blockBoundsDots, EMPTY_TEXT_PLACEHOLDER_GLYPHS, isBlankText, rotatedLineOffset, tbBoundsDots, zebraLineWidthDots } from "./zebraTextLayout";
@@ -344,14 +345,15 @@ export function printableRectDots(label: {
   widthMm: number;
   heightMm: number;
   dpmm: number;
+  jmDensity?: JmDensity;
   labelShift?: number;
 }): BoundingBoxDots {
   const shift = label.labelShift ?? 0;
   return {
     x: shift,
     y: 0,
-    width: mmToDots(label.widthMm, label.dpmm),
-    height: mmToDots(label.heightMm, label.dpmm),
+    width: mmToDots(label.widthMm, effectiveDpmm(label)),
+    height: mmToDots(label.heightMm, effectiveDpmm(label)),
   };
 }
 

packages/core/src/lib/resolveDefaultSize.ts

@@ -1,5 +1,6 @@
 import { mmToDots } from "./coordinates";
 import type { LabelConfig } from "../types/LabelConfig";
+import { effectiveDpmm } from "../types/LabelConfig";
 import type { ObjectTypeCore } from "../types/ObjectType";
 /** Resolve a registry `defaultSize` declaration to dot units against
  *  the active label config. Spec-fixed-physical-size symbols (e.g.
@@ -13,8 +14,8 @@ export function resolveDefaultSizeDots(
 ): { width: number; height: number } {
   if ("widthMm" in defaultSize) {
     return {
-      width: mmToDots(defaultSize.widthMm, label.dpmm),
-      height: mmToDots(defaultSize.heightMm, label.dpmm),
+      width: mmToDots(defaultSize.widthMm, effectiveDpmm(label)),
+      height: mmToDots(defaultSize.heightMm, effectiveDpmm(label)),
     };
   }
   // Shallow-copy the dots-branch so callers can't accidentally