TXFADataStructure Class

TXFADataStructure, declared in HPDFXFADataStructure, maintains bounded structural edits to an existing native XFA node tree and owns any detached element trees created, cloned, or removed through the graph

CreateDataNode serves Data DOM elements, while CreateElement also supports the model-element construction used by TXFAFormStructure

The constructor borrows Root and validates the existing tree against TXFADataStructureLimits before returning; the graph must be destroyed before the owner of the borrowed root

All public AnsiString names, namespace URIs, and text values contain UTF-8 bytes

Graph := TXFADataStructure.Create(DatasetsRoot, Limits, OnTick);
try
  Graph.BeginOperation(OnTick);
  try
    Node := Graph.CreateDataNode('dataValue', 'amount');
    Graph.SetValue(Node, '42');
    Graph.Append(RecordNode, Node);
  finally
    Graph.EndOperation;
  end;
finally
  Graph.Free;
end;

Operation scope

BeginOperation(OnTick) starts a scope and rejects a nested scope; EndOperation releases the stored callback and is safe during cleanup

The constructor runs its own preflight scope and releases the constructor callback before returning; subsequent methods require a new active scope

OnTick is a Delphi anonymous procedure or an FPC nested procedure of type TXFADataStructureTick; it may raise to cancel work or enforce a caller deadline or operation counter

Methods prepare allocations, ownership capacity, and required namespace declarations before their final cancellation check and structural mutation; a rejected individual edit preserves the existing document graph

A series of successful direct graph calls is not automatically rolled back when a later call fails; the scripting runtime supplies the complete event transaction and restores its document, detached graph, script identities, lexical state, and journal together

Creation and cloning

CreateDataNode(ClassName, Name, NamespaceURI = '') accepts dataGroup or dataValue, creates a fresh detached element, and records explicit data-node class metadata

CreateElement(ClassName, Name, NamespaceURI) creates a detached model element whose XML local name is ClassName, with an optional XFA name attribute and an explicit default namespace declaration

CreateElement validates XML syntax, scalar values, reserved namespace URIs, and graph capacity; the higher-level form factory validates the supported XFA class schema

Name may be an XML local name or a qualified name whose nonempty prefix has the supplied nonempty namespace URI; reserved xml and xmlns bindings are validated

An empty name is permitted for a detached construction step; set a valid name with Rename before attachment

Clone(Node, Recursive = True) creates a detached copy with fresh native identities; a shallow copy keeps the element's own value, attributes, and namespace declarations while excluding child nodes

Inherited namespace declarations are materialized before a clone or move so prefixed attributes retain their original namespace outside their previous ancestor scope

Ownership edits

Append(Parent, Node) moves the same node to the end of the parent's ordered children; InsertBefore(Parent, Node, Before) moves it before an existing direct child, with Before = nil equivalent to append

Remove(Parent, Node) detaches the existing direct child and transfers its ownership to the graph; the object, descendants, and native identities remain valid until graph destruction or detached snapshot restoration

Foreign graphs, cycles, moving the borrowed root, unnamed attachment, invalid sibling references, and node/depth/byte overflow raise EHPDFXFAError

Value and name edits

Rename(Node, Name) changes the element's local XML name while retaining its prefix, namespace URI, position, descendants, and native identity; an attached element requires a nonempty valid XML name

SetValue(Node, Value) validates UTF-8 and XML scalar values, replaces ordinary text children, and preserves comments and processing instructions; empty text removes ordinary text children

SetAttribute(Node, Name, Value) adds or replaces an attribute after validating its qualified-name syntax, UTF-8 value, and projected byte budget; an empty value remains an explicit empty attribute

SetNamespace(Node, NamespaceURI) changes the element's expanded namespace and updates the declaration for its current prefix, while validating reserved bindings

DeclareNamespace(Node, Prefix, NamespaceURI) adds or replaces a namespace declaration without changing the element's expanded name; it rejects a conflicting declaration for the element's own prefix

Direct graph callers coordinate prefixed attributes with their namespace declarations and keep compound edits inside their own rollback transaction

The byte and node budgets include the element's aggregate value and its actual owned text node, rather than charging only one representation of the text

XML import preflight

ValidateImport(Node, Incoming, Overwrite, OnTick) checks the projected aggregate graph before a caller imports an owned list of incoming XML children

When Overwrite is true, the projected size excludes the target's replaced children and aggregate value; otherwise existing children remain in the budget

The method leaves the incoming list and document unchanged and creates a temporary operation scope only when no scope is already active

Detached snapshots

CaptureDetached returns a value snapshot of every detached root and descendant, including text, CDATA, comments, processing instructions, attributes, and namespace declarations

RestoreDetached(Snapshot) validates and prepares a replacement detached forest before swapping ownership; its returned node array follows the snapshot order and contains fresh native identities for caller remapping

See TXFADataStructureSnapshot for record fields and identity rules

Inspection

Root exposes the borrowed root and DetachedRoots exposes the graph-owned roots for inspection; use graph methods for changes so ownership and budgets remain coherent

Transactional Data DOM scripting · Transactional form tree scripting · TXFANode