fix(pptx): inherit group fill for <a:grpFill/> shapes (#83)

Shapes using <a:grpFill/> now inherit the enclosing group's resolved fill
instead of collapsing to transparent, so decorative custGeom line-art that
shares one translucent group colour stays visible on import.

Author: karthikmudunuri

.changeset/grpfill-inheritance.md

@@ -0,0 +1,17 @@
+---
+"@textcortex/slidewise": patch
+---
+
+fix(pptx): render `<a:grpFill/>` shapes by inheriting the group's fill
+
+Decorative line-art (e.g. the swoosh graphic on a title slide) is often
+authored as many `<a:custGeom>` segments inside a single `<p:grpSp>`, with every
+segment declaring `<a:grpFill/>` so they share the group's one translucent
+colour. `parsePptx` had no `grpFill` branch, so each segment fell through to
+`transparent` and the entire graphic disappeared on import — present in the
+source but invisible in the deck.
+
+The group's resolved fill is now threaded down to descendants, and a shape with
+`<a:grpFill/>` paints with it (walking up the group chain when an inner group
+defines no fill of its own). Geometry was already preserved; only the paint was
+being dropped.

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

@@ -0,0 +1,77 @@
+import { describe, it, expect } from "vitest";
+import JSZip from "jszip";
+import { parsePptx } from "../index";
+import type { SlideElement } from "@/lib/types";
+
+/**
+ * `<a:grpFill/>` means "paint with the enclosing group's fill". Decorative
+ * line-art (e.g. the swoosh graphic on a title slide) is commonly authored as
+ * many `<a:custGeom>` segments inside one `<p:grpSp>`, with every segment
+ * declaring `<a:grpFill/>` so they share the group's single translucent
+ * colour. If the importer doesn't resolve grpFill the segments fall through to
+ * transparent and the whole graphic disappears. This guards that inheritance.
+ */
+function baseZip(): JSZip {
+  const zip = new JSZip();
+  zip.file(
+    "[Content_Types].xml",
+    `<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
+  <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+  <Default Extension="xml" ContentType="application/xml"/>
+  <Override PartName="/ppt/presentation.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.presentation.main+xml"/>
+  <Override PartName="/ppt/slides/slide1.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.slide+xml"/>
+</Types>`
+  );
+  zip.file(
+    "_rels/.rels",
+    `<?xml version="1.0" encoding="UTF-8" standalone="yes"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="ppt/presentation.xml"/></Relationships>`
+  );
+  zip.file(
+    "ppt/presentation.xml",
+    `<?xml version="1.0" encoding="UTF-8" standalone="yes"?><p:presentation xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"><p:sldIdLst><p:sldId id="256" r:id="rId2"/></p:sldIdLst><p:sldSz cx="12192000" cy="6858000"/></p:presentation>`
+  );
+  zip.file(
+    "ppt/_rels/presentation.xml.rels",
+    `<?xml version="1.0" encoding="UTF-8" standalone="yes"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId2" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide" Target="slides/slide1.xml"/></Relationships>`
+  );
+  zip.file(
+    "ppt/slides/_rels/slide1.xml.rels",
+    `<?xml version="1.0" encoding="UTF-8" standalone="yes"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"></Relationships>`
+  );
+  return zip;
+}
+
+function flatten(els: SlideElement[]): SlideElement[] {
+  return els.flatMap((e) =>
+    e.type === "group" ? [e, ...flatten(e.children)] : [e]
+  );
+}
+
+const NS =
+  `xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main" xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main"`;
+
+describe("grpFill inheritance", () => {
+  it("a <a:grpFill/> shape inherits its group's solid fill", async () => {
+    const zip = baseZip();
+    // Group carries a red solid fill; its custGeom child declares <a:grpFill/>
+    // and no fill of its own, so it must render red.
+    zip.file(
+      "ppt/slides/slide1.xml",
+      `<?xml version="1.0" encoding="UTF-8" standalone="yes"?><p:sld ${NS}><p:cSld><p:spTree><p:grpSp><p:nvGrpSpPr><p:cNvPr id="2" name="g"/><p:cNvGrpSpPr/><p:nvPr/></p:nvGrpSpPr><p:grpSpPr><a:xfrm><a:off x="0" y="0"/><a:ext cx="2000000" cy="2000000"/><a:chOff x="0" y="0"/><a:chExt cx="2000000" cy="2000000"/></a:xfrm><a:solidFill><a:srgbClr val="FF0000"/></a:solidFill></p:grpSpPr><p:sp><p:nvSpPr><p:cNvPr id="3" name="seg"/><p:cNvSpPr/><p:nvPr/></p:nvSpPr><p:spPr><a:xfrm><a:off x="0" y="0"/><a:ext cx="1000000" cy="1000000"/></a:xfrm><a:custGeom><a:avLst/><a:gdLst/><a:rect l="0" t="0" r="0" b="0"/><a:pathLst><a:path w="1000000" h="1000000"><a:moveTo><a:pt x="0" y="0"/></a:moveTo><a:lnTo><a:pt x="1000000" y="0"/></a:lnTo><a:lnTo><a:pt x="1000000" y="1000000"/></a:lnTo><a:close/></a:path></a:pathLst></a:custGeom><a:grpFill/><a:ln><a:noFill/></a:ln></p:spPr></p:sp></p:grpSp></p:spTree></p:cSld></p:sld>`
+    );
+
+    const buffer = await zip.generateAsync({ type: "arraybuffer" });
+    const deck = await parsePptx(buffer);
+    const shape = flatten(deck.slides[0].elements).find(
+      (e) => e.type === "shape"
+    );
+    expect(shape).toBeTruthy();
+    if (shape && shape.type === "shape") {
+      // Inherited the group's red fill rather than collapsing to transparent.
+      expect(String(shape.fill).toUpperCase()).toContain("FF0000");
+      // The custGeom silhouette is preserved so it draws as line-art, not a box.
+      expect(shape.path).toBeTruthy();
+    }
+  });
+});

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

@@ -975,6 +975,13 @@ interface GroupTransform {
   b: number;
   c: number;
   d: number;
+  /**
+   * The enclosing `<p:grpSp>`'s resolved fill, threaded down so descendant
+   * shapes that declare `<a:grpFill/>` ("inherit my fill from the group") can
+   * paint with it. Undefined at the slide root and inside groups that define
+   * no fill of their own. See the `p:grpSp` branch in {@link parseSpTree}.
+   */
+  groupFill?: string;
 }
 
 function identityTransform(): GroupTransform {
@@ -1046,7 +1053,13 @@ async function parseSpTree(
       }
     } else if (tag === "p:grpSp") {
       const inner = composeGroupTransform(node, outer);
-      const children = await parseSpTree(node, ctx, inner);
+      // Resolve this group's own fill so descendant shapes that use
+      // `<a:grpFill/>` (inherit-from-group) can paint with it. A group that
+      // omits a fill inherits the enclosing group's, matching PowerPoint's
+      // walk up the group chain.
+      const groupFill =
+        extractShapeFill(node?.["p:grpSpPr"], ctx.theme) ?? outer.groupFill;
+      const children = await parseSpTree(node, ctx, { ...inner, groupFill });
       if (!children.length) continue;
       const group = buildGroupElement(node, children, ctx, outer);
       // Register the whole `<p:grpSp>` so an unedited group round-trips
@@ -1367,9 +1380,16 @@ async function parseSpOrText(
   // it carries the actual art. Resolved to a url("data:…") the renderer
   // paints into the shape (clipped to its custGeom path when present).
   const blipFill = await extractShapeBlipFill(spPr, ctx);
+  // `<a:grpFill/>` means "paint with the enclosing group's fill". The group's
+  // resolved fill is threaded in via `outer.groupFill`; without this the shape
+  // falls through to transparent and disappears (e.g. decorative custGeom
+  // line-art whose every segment inherits one translucent group colour).
+  const grpFill =
+    spPr?.["a:grpFill"] !== undefined ? outer.groupFill : undefined;
   const fillColor =
     blipFill
     ?? extractShapeFill(spPr, ctx.theme)
+    ?? grpFill
     ?? (phSpPr ? extractShapeFill(phSpPr, ctx.theme) : undefined)
     ?? resolveStyleFillRef(sp, ctx)
     ?? "transparent";