Add a unit-test for the Catalog.#getDestFromStructElement method

This code already has an integration-test, however also having a unit-test shouldn't hurt since those are often easier to run and debug (and it nicely complements the existing `outline` unit-tests).

The patch also makes the following smaller changes to the method itself:
 - Avoid creating and parsing an empty Array, when doing the `pageRef` search.
 - Use `XRef.prototype.fetch` directly, when walking the parent chain, since the check just above ensures that the value is a Reference.
 - Use the `lookupRect` helper when parsing the /BBox entry.

Author: Snuffleupagus

src/core/catalog.js

@@ -29,6 +29,7 @@ import {
 import {
   collectActions,
   isNumberArray,
+  lookupRect,
   MissingDataException,
   PDF_VERSION_REGEXP,
   recoverJsURL,
@@ -1597,7 +1598,7 @@ class Catalog {
         } else if (kids) {
           kidsArr = [kids];
         } else {
-          kidsArr = [];
+          continue;
         }
         for (const kid of kidsArr) {
           const kidObj = xref.fetchIfRef(kid);
@@ -1623,7 +1624,7 @@ class Catalog {
         if (!(parentRaw instanceof Ref)) {
           break;
         }
-        const parentDict = xref.fetchIfRef(parentRaw);
+        const parentDict = xref.fetch(parentRaw);
         if (!(parentDict instanceof Dict)) {
           break;
         }
@@ -1648,10 +1649,10 @@ class Catalog {
       y = null;
     const attrs = seDict.get("A");
     if (attrs instanceof Dict) {
-      const bboxArr = attrs.getArray("BBox");
-      if (isNumberArray(bboxArr, 4)) {
-        x = bboxArr[0];
-        y = bboxArr[3]; // top of the bbox in PDF page coordinates
+      const bbox = lookupRect(attrs.getArray("BBox"), null);
+      if (bbox) {
+        x = bbox[0];
+        y = bbox[3]; // top of the bbox in PDF page coordinates
       }
     }
 

test/unit/api_spec.js

@@ -2167,6 +2167,65 @@ describe("api", function () {
       await loadingTask.destroy();
     });
 
+    it("gets outline, with SE (Structure Element) entries", async function () {
+      const loadingTask = getDocument(
+        buildGetDocumentParams("outlines_se.pdf")
+      );
+      const pdfDoc = await loadingTask.promise;
+      const outline = await pdfDoc.getOutline();
+
+      expect(outline).toEqual([
+        {
+          action: null,
+          attachment: undefined,
+          dest: null,
+          url: null,
+          unsafeUrl: undefined,
+          newWindow: undefined,
+          setOCGState: undefined,
+          title: "P tags",
+          color: new Uint8ClampedArray([0, 0, 0]),
+          count: 2,
+          bold: false,
+          italic: false,
+          items: [
+            {
+              action: null,
+              attachment: undefined,
+              dest: [{ num: 37, gen: 0 }, { name: "XYZ" }, null, null, null],
+              url: null,
+              unsafeUrl: undefined,
+              newWindow: undefined,
+              setOCGState: undefined,
+              title: "Hello ",
+              color: new Uint8ClampedArray([0, 0, 0]),
+              count: undefined,
+              bold: false,
+              italic: false,
+              items: [],
+            },
+            {
+              action: null,
+              attachment: undefined,
+              dest: [{ num: 36, gen: 0 }, { name: "XYZ" }, null, null, null],
+              url: null,
+              unsafeUrl: undefined,
+              newWindow: undefined,
+              setOCGState: undefined,
+              title: "World ",
+              color: new Uint8ClampedArray([0, 0, 0]),
+              count: undefined,
+              bold: false,
+              italic: false,
+              items: [],
+            },
+          ],
+        },
+      ]);
+
+      await loadingTask.destroy();
+    });
+
     it("gets non-existent permissions", async function () {
       const permissions = await pdfDocument.getPermissions();
       expect(permissions).toEqual(null);