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LibPDF: Parse nested Page Tree structures

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We now follow nested page tree nodes to find all of the actual
page dicts, whereas previously we just assumed the root level
page tree node contained all of the page children directly.
This commit is contained in:
Matthew Olsson 2021-05-02 18:53:07 -07:00 • committed by Andreas Kling
parent 8c745ad0d9
commit 3aeaceb727
4 changed files with 77 additions and 5 deletions
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25
Userland/Libraries/LibPDF/Document.cpp
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@ -117,14 +117,33 @@ UnwrappedValueType<T> Document::resolve_to(const Value& value)
void Document::build_page_tree()
{
auto page_tree = m_catalog->get_dict(this, "Pages");
auto kids_array = page_tree->get_array(this, "Kids");
add_page_tree_node_to_page_tree(page_tree);
}
void Document::add_page_tree_node_to_page_tree(NonnullRefPtr<DictObject> page_tree)
{
auto kids_array = page_tree->get_array(this, "Kids");
auto page_count = page_tree->get("Count").value().as_int();
if (static_cast<size_t>(page_count) != kids_array->elements().size()) {
// FIXME: Support recursive PDF page tree structures
VERIFY_NOT_REACHED();
// This page tree contains child page trees, so we recursively add
// these pages to the overall page tree
for (auto& value : *kids_array) {
auto reference = resolve_to<IndirectValueRef>(value);
auto byte_offset = m_xref_table.byte_offset_for_object(reference->index());
auto maybe_page_tree_node = m_parser.conditionally_parse_page_tree_node_at_offset(byte_offset);
if (maybe_page_tree_node) {
add_page_tree_node_to_page_tree(maybe_page_tree_node.release_nonnull());
} else {
m_page_object_indices.append(reference->index());
}
}
return;
}
// We know all of the kids are leaf nodes
for (auto& value : *kids_array) {
auto reference = resolve_to<IndirectValueRef>(value);
m_page_object_indices.append(reference->index());