awaforge

pdfParentTree

AGPL-3.0-onlyRelease 2L4

ParentTree — ISO 32000-2 §14.7.5 — number tree, MCID → struct element / OBJR.

Module pdfParentTree | Source packages/front/office/pdf/src/tagged/parentTree.js | Deps pdfErrors, pdfParser | Worker-safe yes

The StructTreeRoot's /ParentTree is a number tree (§7.9.7) mapping StructParents/StructParent keys (on pages, annotations, content-stream objects) to their parent structure elements. The module provides lookupParent(tree, key, resolveRef, opts?), which descends /Kids nodes (checking /Limits) then scans /Nums leaves until key is found. Returns either a single ref (annotations/form XObjects) or an array indexed by MCID (pages).

Resolve

const pt = runtime.resolve('pdfParentTree');
// Returns: { lookupParent }

API

Method Signature Returns
lookupParent (tree, key: number, resolveRef, opts?: { maxDepth? }) => PdfObject | null Value of the number tree for key.

opts.maxDepth defaults to 32. Returns null when key is not found.

Examples

Finding the struct elem of an MCID on a page

const pt = runtime.resolve('pdfParentTree');
const page = doc.pages[0];
const parents = pt.lookupParent(structRoot.parentTree, page.structParents, resolveRef);
// parents is an array PdfObject: parents.items[mcid] -> ref to the StructElement
const elemRef = parents.items[42];

Parent of an annotation

const annotParent = pt.lookupParent(parentTree, annot.structParent, resolveRef);
// direct ref to the StructElement

Errors

Code Class When
pdf/tagged/parent-tree/max-depth ParseError Depth exceeds opts.maxDepth.
pdf/tagged/parent-tree/not-dict ParseError Node is not a dict.
pdf/tagged/parent-tree/non-ref-kid ParseError /Kids contains a non-ref entry.
pdf/tagged/parent-tree/bad-child ParseError Resolved child is not a dict.
pdf/tagged/parent-tree/empty-node ParseError Node has neither /Kids nor /Nums.
pdf/tagged/parent-tree/bad-nums ParseError /Nums is not an even-length array.
pdf/tagged/parent-tree/bad-key ParseError /Nums key is not a number.
pdf/tagged/parent-tree/bad-limits ParseError /Limits malformed.

See also