LibPDF: Add initial implementation of XObject rendering

This implementation currently handles Form XObjects only, skipping
image XObjects. When rendering an XObject, its resources are passed to
the underlying operations so they use those instead of the Page's.

Userland/Libraries/LibPDF/Renderer.cpp

@@ -620,7 +620,38 @@ RENDERER_TODO(shade)
 RENDERER_TODO(inline_image_begin)
 RENDERER_TODO(inline_image_begin_data)
 RENDERER_TODO(inline_image_end)
-RENDERER_TODO(paint_xobject)
+RENDERER_HANDLER(paint_xobject)
+{
+    VERIFY(args.size() > 0);
+    auto resources = extra_resources.value_or(m_page.resources);
+    auto xobject_name = args[0].get<NonnullRefPtr<Object>>()->cast<NameObject>()->name();
+    auto xobjects_dict = MUST(resources->get_dict(m_document, CommonNames::XObject));
+    auto xobject = MUST(xobjects_dict->get_stream(m_document, xobject_name));
+
+    auto subtype = MUST(xobject->dict()->get_name(m_document, CommonNames::Subtype))->name();
+    if (subtype == CommonNames::Image) {
+        dbgln("Skipping image");
+        return {};
+    }
+
+    MUST(handle_save_state({}));
+    Vector<Value> matrix;
+    if (xobject->dict()->contains(CommonNames::Matrix)) {
+        matrix = xobject->dict()->get_array(m_document, CommonNames::Matrix).value()->elements();
+    } else {
+        matrix = Vector { Value { 1 }, Value { 0 }, Value { 0 }, Value { 1 }, Value { 0 }, Value { 0 } };
+    }
+    MUST(handle_concatenate_matrix(matrix));
+    Optional<NonnullRefPtr<DictObject>> xobject_resources {};
+    if (xobject->dict()->contains(CommonNames::Resources)) {
+        xobject_resources = xobject->dict()->get_dict(m_document, CommonNames::Resources).value();
+    }
+    auto operators = TRY(Parser::parse_operators(m_document, xobject->bytes()));
+    for (auto& op : operators)
+        TRY(handle_operator(op, xobject_resources));
+    MUST(handle_restore_state({}));
+    return {};
+}
 
 RENDERER_HANDLER(marked_content_point)
 {