fix(pptx): carry verbatim custGeom OOXML in deck JSON for cross-process serialize (#69)

Author: karthikmudunuri

.changeset/custgeom-verbatim-roundtrip.md

@@ -0,0 +1,9 @@
+---
+"@textcortex/slidewise": patch
+---
+
+fix(pptx): carry verbatim custGeom OOXML in the deck JSON so vector shapes survive cross-process serialize
+
+The high-fidelity replay of imported elements relies on two **module-global** registries (`sourceBufferCache`, `elementSourceRegistry`) populated only by `parsePptx` and never written to the deck JSON. In a pipeline that parses in one process and serializes in another (parse client-side → store deck JSON → serialize server-side), those registries are empty, so every element is re-synthesised from its deck fields. Synthesis can't represent OOXML even-odd / winding, so complex `custGeom` vectors (e.g. a bicycle diagram) render blank even though simpler ones (the brand logo) happen to survive.
+
+The importer now stamps the verbatim `<p:sp>` of **self-contained** custGeom shapes (no `r:embed` / `r:id` / `a:schemeClr` references) onto the element as `pristineOoxml = { xml, snapshot }`, which rides along in the deck JSON. On serialize, an unedited such shape (snapshot still matches) is replayed verbatim — exact source geometry and winding — instead of being re-synthesised; its `cNvPr/@id` is rewritten to avoid spTree collisions. Edited shapes fall back to synthesis. This is the same persist-in-JSON pattern already used for embedded fonts (`deck.fonts`), scoped to vector shapes to keep JSON bloat negligible (~a few KB per deck).

packages/slidewise/src/lib/pptx/__tests__/roundtrip.test.ts

@@ -247,6 +247,44 @@ describe("pptx round-trip", () => {
     ).toBe(true);
   });
 
+  it("stamps verbatim pristineOoxml on imported self-contained custGeom shapes", async () => {
+    // Round a custGeom shape (solid fill, no scheme/rId refs) through a real
+    // serialize→parse. The importer should carry its verbatim <p:sp> in the
+    // deck JSON so a later cross-process serialize can replay it.
+    const deck = makeDeck([
+      {
+        ...baseElement,
+        id: "logo",
+        type: "shape",
+        x: 100,
+        y: 100,
+        w: 400,
+        h: 300,
+        shape: "rect",
+        fill: "#EA1B0A",
+        path: {
+          d: "M 0 0 L 100 0 L 100 100 L 0 100 Z",
+          viewW: 100,
+          viewH: 100,
+          fillRule: "evenodd",
+        },
+      },
+    ]);
+
+    const out = await roundtrip(deck);
+    const shape = out.slides[0].elements.find(
+      (e) => e.type === "shape" && e.path
+    );
+    expect(shape && shape.type === "shape").toBe(true);
+    if (!shape || shape.type !== "shape") return;
+    expect(shape.pristineOoxml).toBeTruthy();
+    expect(shape.pristineOoxml?.xml).toContain("<a:custGeom>");
+    // The stored snapshot matches the element as imported (so the serializer
+    // treats it as pristine until edited).
+    expect(typeof shape.pristineOoxml?.snapshot).toBe("string");
+    expect(shape.pristineOoxml?.snapshot.length).toBeGreaterThan(0);
+  });
+
   it("preserves slide background colour", async () => {
     const deck: Deck = {
       version: CURRENT_DECK_VERSION,

packages/slidewise/src/lib/pptx/__tests__/synth-writers.test.ts

@@ -1,8 +1,9 @@
 import { describe, it, expect } from "vitest";
 import JSZip from "jszip";
 import { serializeDeck } from "../index";
+import { snapshotElement } from "../pptxToDeck";
 import { CURRENT_DECK_VERSION } from "@/lib/schema/migrate";
-import type { Deck } from "@/lib/types";
+import type { Deck, ShapeElement } from "@/lib/types";
 
 /**
  * Tests for the synth-OOXML writers added in the full-fidelity export work:
@@ -102,6 +103,75 @@ describe("synth writers (PRs 1, 2, 3, 4, 5, 6, 7)", () => {
     expect(slide).not.toMatch(/<a:prstGeom prst="rect"/);
   });
 
+  it("replays verbatim custGeom OOXML from the deck JSON when present (cross-process)", async () => {
+    const shape: ShapeElement = {
+      ...base,
+      id: "bikeXYZ",
+      type: "shape",
+      shape: "rect",
+      x: 100,
+      y: 100,
+      w: 400,
+      h: 300,
+      fill: "#EA1B0A",
+      path: {
+        d: "M 0 0 L 100 0 L 100 100 Z",
+        viewW: 100,
+        viewH: 100,
+        fillRule: "evenodd",
+      },
+    };
+    // Self-contained verbatim <p:sp> with a colliding low cNvPr id + a marker.
+    const verbatim =
+      `<p:sp><p:nvSpPr><p:cNvPr id="7" name="bike"/><p:cNvSpPr/><p:nvPr/></p:nvSpPr>` +
+      `<p:spPr><a:xfrm><a:off x="635000" y="635000"/><a:ext cx="2540000" cy="1905000"/></a:xfrm>` +
+      `<a:custGeom data-marker="VERBATIM_BIKE"><a:pathLst><a:path w="100" h="100">` +
+      `<a:moveTo><a:pt x="0" y="0"/></a:moveTo><a:lnTo><a:pt x="100" y="0"/></a:lnTo><a:close/>` +
+      `</a:path></a:pathLst></a:custGeom>` +
+      `<a:solidFill><a:srgbClr val="EA1B0A"/></a:solidFill></p:spPr>` +
+      `<p:txBody><a:bodyPr/><a:lstStyle/><a:p/></p:txBody></p:sp>`;
+    shape.pristineOoxml = { xml: verbatim, snapshot: snapshotElement(shape) };
+
+    const zip = await generate(
+      makeDeck([{ id: "s", background: "#FFFFFF", elements: [shape] }])
+    );
+    const slide = await zip.file("ppt/slides/slide1.xml")?.async("string");
+    // The exact source geometry was replayed (marker + source fill present)…
+    expect(slide).toContain('data-marker="VERBATIM_BIKE"');
+    expect(slide).toContain('<a:srgbClr val="EA1B0A"/>');
+    // …and the colliding cNvPr id="7" was rewritten to a fresh high id.
+    expect(slide).not.toMatch(/<p:cNvPr\b[^>]*\bid="7"/);
+  });
+
+  it("falls back to synthesis when a pristine-OOXML shape was edited", async () => {
+    const shape: ShapeElement = {
+      ...base,
+      id: "bikeEdited",
+      type: "shape",
+      shape: "rect",
+      x: 100,
+      y: 100,
+      w: 400,
+      h: 300,
+      fill: "#EA1B0A",
+      path: { d: "M 0 0 L 100 0 L 100 100 Z", viewW: 100, viewH: 100 },
+    };
+    const verbatim =
+      `<p:sp><p:nvSpPr><p:cNvPr id="7" name="bike"/><p:cNvSpPr/><p:nvPr/></p:nvSpPr>` +
+      `<p:spPr><a:custGeom data-marker="VERBATIM_BIKE"/></p:spPr></p:sp>`;
+    shape.pristineOoxml = { xml: verbatim, snapshot: snapshotElement(shape) };
+    // Edit the shape AFTER the snapshot was taken → snapshot diverges.
+    shape.x = 999;
+
+    const zip = await generate(
+      makeDeck([{ id: "s", background: "#FFFFFF", elements: [shape] }])
+    );
+    const slide = await zip.file("ppt/slides/slide1.xml")?.async("string");
+    // Verbatim replay is rejected; the synth path emits the custGeom from path.d.
+    expect(slide).not.toContain("VERBATIM_BIKE");
+    expect(slide).toContain("<a:custGeom>");
+  });
+
   it("PR 2: emits <a:gradFill> for shapes with linear-gradient fill", async () => {
     const deck = makeDeck([
       {

packages/slidewise/src/lib/pptx/deckToPptx.ts

@@ -32,6 +32,7 @@ import {
   synthesiseEmbeddedFonts,
   effectLstXml,
   parseFill,
+  freshNvId,
   RID_MARKER_RE,
   slidewiseShapeName,
   type MediaPayload,
@@ -167,6 +168,16 @@ function shouldSynthesise(el: SlideElement): boolean {
 
 function synthesiseInto(synth: SynthSlideEntry, el: SlideElement): void {
   if (el.type === "shape") {
+    // Cross-process replay: an unedited custGeom shape carries its verbatim
+    // source `<p:sp>` in the deck JSON (see `stampPristineOoxml`). Replaying
+    // it preserves the exact source winding/geometry that synthesis can't —
+    // this is what un-blanks complex vectors when the import-time source
+    // registry isn't available (parse + serialize in different processes).
+    const verbatim = pristineShapeXml(el);
+    if (verbatim) {
+      synth.shapeXml.push(verbatim);
+      return;
+    }
     const out = synthesiseShape(el);
     synth.shapeXml.push(out.xml);
     for (const m of out.media) synth.media.push(m);
@@ -187,6 +198,26 @@ function synthesiseInto(synth: SynthSlideEntry, el: SlideElement): void {
   }
 }
 
+/**
+ * Verbatim `<p:sp>` for a custGeom shape that carries deck-JSON-persisted
+ * source OOXML and hasn't been edited. Returns null when there's no pristine
+ * XML or the element diverged from its import snapshot (then the caller
+ * synthesises from `path.d`). The source `cNvPr/@id` is rewritten to a fresh
+ * high id so it can't collide with whatever pptxgenjs allocated in the spTree.
+ *
+ * NB: same-process serialize never reaches here for these shapes — they're
+ * caught earlier by `isPristineImportedElement` (registry hit) and replayed
+ * through the source archive. This path is the cross-process fallback.
+ */
+function pristineShapeXml(el: SlideElement): string | null {
+  if (el.type !== "shape" || !el.pristineOoxml) return null;
+  if (snapshotElement(el) !== el.pristineOoxml.snapshot) return null;
+  return el.pristineOoxml.xml.replace(
+    /(<p:cNvPr\b[^>]*\bid=")\d+(")/,
+    `$1${freshNvId()}$2`
+  );
+}
+
 /**
  * Render a single child for `<p:grpSp>`. We only synthesise shapes/charts
  * inside groups for v1 — text / image / line children remain renderable

packages/slidewise/src/lib/pptx/pptxToDeck.ts

@@ -480,6 +480,25 @@ function registerElementSource(
     snapshot: snapshotElement(element),
     slidePath,
   });
+  stampPristineOoxml(element, rawXml);
+}
+
+/**
+ * For a self-contained custGeom (vector) shape, copy its verbatim `<p:sp>`
+ * source XML onto the element so it survives JSON serialization (the
+ * `elementSourceRegistry` above is module-global and lost across processes).
+ * A serialize in a fresh process can then replay the exact source geometry
+ * instead of re-synthesising from `path.d` — synthesis can't represent OOXML
+ * even-odd winding, which is what blanks complex vectors like the eon bicycle.
+ *
+ * Restricted to shapes whose XML carries no external references
+ * (`r:embed` / `r:id` / `r:link` images, `a:schemeClr` theme colours) so the
+ * fragment stays valid without the source archive or its theme.
+ */
+function stampPristineOoxml(element: SlideElement, rawXml: string): void {
+  if (element.type !== "shape" || !element.path) return;
+  if (/\br:(embed|id|link)=|<a:schemeClr\b/.test(rawXml)) return;
+  element.pristineOoxml = { xml: rawXml, snapshot: snapshotElement(element) };
 }
 
 function hasExplicitXfrm(xml: string): boolean {

packages/slidewise/src/lib/types.ts

@@ -205,6 +205,21 @@ export interface ShapeElement extends BaseElement {
    * `shape` field remains as a sensible fallback for older renderers.
    */
   path?: ShapePath;
+  /**
+   * Verbatim `<p:sp>` OOXML captured at import for a self-contained custGeom
+   * (vector) shape, carried *in the deck JSON* so a serialize running in a
+   * different process from the import (parse client-side → store JSON →
+   * serialize server-side) can replay the exact source geometry rather than
+   * re-synthesising from `path.d`. Synthesis can't express OOXML even-odd /
+   * winding faithfully, so complex vectors blank when the process-global
+   * source registry isn't available. Only populated for shapes whose source
+   * XML has no external references (`r:embed` / `r:id` / `a:schemeClr`), so it
+   * stays valid without the source archive or theme. `snapshot` is the element
+   * snapshot at import; the serializer replays the XML only while the element
+   * is unedited (snapshot still matches), otherwise it falls back to synthesis.
+   * Host-opaque — do not author by hand.
+   */
+  pristineOoxml?: { xml: string; snapshot: string };
 }
 
 export interface ShapePath {