Preserve QPowerPoint slide transitions in PPTX

src/io/powerPointOffice.ts

@@ -38,6 +38,7 @@ const slideRelationshipType = "http://schemas.openxmlformats.org/officeDocument/
 const notesRelationshipType = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/notesSlide";
 const imageRelationshipType = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/image";
 const emuPerInch = 914400;
+const slideTransitions = ["fade", "push", "wipe"] as const;
 const themeColors: Record<Slide["theme"], { background: string; title: string; subtitle: string }> = {
   classic: { background: "FFFFFF", title: "202124", subtitle: "3C4043" },
   ocean: { background: "EAF6FF", title: "075985", subtitle: "0F766E" },
@@ -75,6 +76,7 @@ export async function importPptxFile(file: File): Promise<ImportedPowerPointDeck
         : "";
       const backgroundColor = slideBackgroundColor(parsedSlide);
       const hidden = slideHidden(parsedSlide);
+      const transition = slideTransition(parsedSlide);
 
       return {
         id: `pptx-slide-${index}`,
@@ -83,6 +85,7 @@ export async function importPptxFile(file: File): Promise<ImportedPowerPointDeck
         notes,
         theme: "classic" as const,
         ...(hidden ? { hidden } : {}),
+        ...(transition ? { transition } : {}),
         ...(backgroundColor ? { backgroundColor } : {}),
         ...(slideTextBlocks[0]?.color ? { titleColor: slideTextBlocks[0].color } : {}),
         ...(slideTextBlocks[0]?.fontSize ? { titleFontSize: slideTextBlocks[0].fontSize } : {}),
@@ -180,7 +183,7 @@ export async function exportPptxBlob(deck: ExportablePowerPointDeck): Promise<Bl
 
   const result = await pptx.write({ outputType: "blob" });
   const blob = result instanceof Blob ? result : new Blob([result], { type: PPTX_MIME_TYPE });
-  return deck.slides.some((slide) => slide.hidden) ? applyHiddenSlidesToPptxBlob(blob, deck.slides) : blob;
+  return deck.slides.some((slide) => slide.hidden || slide.transition) ? applySlideXmlOverridesToPptxBlob(blob, deck.slides) : blob;
 }
 
 export function extractTextBlocks(xmlNode: unknown): string[] {
@@ -464,19 +467,29 @@ function slideHidden(slideXml: unknown) {
   return isFalseXmlBoolean(slide.show ?? slide["@_show"]);
 }
 
-async function applyHiddenSlidesToPptxBlob(blob: Blob, slides: Slide[]) {
+function slideTransition(slideXml: unknown): Slide["transition"] | undefined {
+  const transition = childRecord(childRecord(slideXml, "sld"), "transition");
+  const type = Object.keys(transition).find((key) => isSlideTransition(key));
+  return isSlideTransition(type) ? type : undefined;
+}
+
+function isSlideTransition(value: unknown): value is NonNullable<Slide["transition"]> {
+  return typeof value === "string" && (slideTransitions as readonly string[]).includes(value);
+}
+
+async function applySlideXmlOverridesToPptxBlob(blob: Blob, slides: Slide[]) {
   const JSZip = await loadJsZip();
   const zip = await JSZip.loadAsync(await blob.arrayBuffer());
   await Promise.all(
     slides.map(async (slide, index) => {
-      if (!slide.hidden) {
+      if (!slide.hidden && !slide.transition) {
         return;
       }
 
       const path = `ppt/slides/slide${index + 1}.xml`;
       const xml = await zip.file(path)?.async("string");
       if (xml) {
-        zip.file(path, pptxSlideXmlWithHiddenState(xml));
+        zip.file(path, pptxSlideXmlWithOverrides(xml, slide));
       }
     })
   );
@@ -484,6 +497,11 @@ async function applyHiddenSlidesToPptxBlob(blob: Blob, slides: Slide[]) {
   return zip.generateAsync({ type: "blob", mimeType: PPTX_MIME_TYPE });
 }
 
+function pptxSlideXmlWithOverrides(xml: string, slide: Slide) {
+  const withHiddenState = slide.hidden ? pptxSlideXmlWithHiddenState(xml) : xml;
+  return slide.transition ? pptxSlideXmlWithTransition(withHiddenState, slide.transition) : withHiddenState;
+}
+
 function pptxSlideXmlWithHiddenState(xml: string) {
   return xml.replace(/<p:sld\b([^>]*)>/, (_match, attributes: string) => {
     const withoutShow = attributes.replace(/\sshow="[^"]*"/, "");
@@ -491,6 +509,21 @@ function pptxSlideXmlWithHiddenState(xml: string) {
   });
 }
 
+function pptxSlideXmlWithTransition(xml: string, transition: NonNullable<Slide["transition"]>) {
+  const transitionXml = `<p:transition><p:${transition}/></p:transition>`;
+  if (/<p:transition\b[\s\S]*?<\/p:transition>/.test(xml)) {
+    return xml.replace(/<p:transition\b[\s\S]*?<\/p:transition>/, transitionXml);
+  }
+  if (/<p:transition\b[^>]*\/>/.test(xml)) {
+    return xml.replace(/<p:transition\b[^>]*\/>/, transitionXml);
+  }
+  if (/<\/p:cSld>/.test(xml)) {
+    return xml.replace("</p:cSld>", `</p:cSld>${transitionXml}`);
+  }
+
+  return xml.replace(/<p:sld\b[^>]*>/, (match) => `${match}${transitionXml}`);
+}
+
 function normalizeHexColor(value?: string) {
   const raw = value?.trim().replace(/^#/, "").toUpperCase() ?? "";
   return /^[0-9A-F]{6}$/.test(raw) ? raw : "";