XFA - Add a layer to display XFA forms (#13069)

- add an option to enable XFA rendering if any;
  - for now, let the canvas layer: it could be useful to implement XFAF forms (embedded pdf in xml stream for the background and xfa form for the foreground);
  - ui elements in template DOM are pretty close to their html counterpart so we generate a fake html DOM from template one:
    - it makes easier to translate template properties to html ones;
    - it makes faster the creation of the html element in the main thread.

src/display/api.js

@@ -162,6 +162,8 @@ function setPDFNetworkStreamFactory(pdfNetworkStreamFactory) {
  *   parsed font data from the worker-thread. This may be useful for debugging
  *   purposes (and backwards compatibility), but note that it will lead to
  *   increased memory usage. The default value is `false`.
+ * @property {boolean} [enableXfa] - Render Xfa forms if any.
+ *   The default value is `false`.
  * @property {HTMLDocument} [ownerDocument] - Specify an explicit document
  *   context to create elements with and to load resources, such as fonts,
  *   into. Defaults to the current document.
@@ -284,6 +286,7 @@ function getDocument(src) {
   params.ignoreErrors = params.stopAtErrors !== true;
   params.fontExtraProperties = params.fontExtraProperties === true;
   params.pdfBug = params.pdfBug === true;
+  params.enableXfa = params.enableXfa === true;
 
   if (!Number.isInteger(params.maxImageSize)) {
     params.maxImageSize = -1;
@@ -438,6 +441,7 @@ function _fetchDocument(worker, source, pdfDataRangeTransport, docId) {
       ignoreErrors: source.ignoreErrors,
       isEvalSupported: source.isEvalSupported,
       fontExtraProperties: source.fontExtraProperties,
+      enableXfa: source.enableXfa,
     })
     .then(function (workerId) {
       if (worker.destroyed) {
@@ -674,6 +678,13 @@ class PDFDocumentProxy {
     return this._pdfInfo.fingerprint;
   }
 
+  /**
+   * @type {boolean} True if only XFA form.
+   */
+  get isPureXfa() {
+    return this._pdfInfo.isPureXfa;
+  }
+
   /**
    * @param {number} pageNumber - The page number to get. The first page is 1.
    * @returns {Promise<PDFPageProxy>} A promise that is resolved with
@@ -1165,6 +1176,16 @@ class PDFPageProxy {
     ));
   }
 
+  /**
+   * @returns {Promise<Object | null>} A promise that is resolved with
+   *   an {Object} with a fake DOM object (a tree structure where elements
+   *   are {Object} with a name, attributes (class, style, ...), value and
+   *   children, very similar to a HTML DOM tree), or `null` if no XFA exists.
+   */
+  getXfa() {
+    return (this._xfaPromise ||= this._transport.getPageXfa(this._pageIndex));
+  }
+
   /**
    * Begins the process of rendering a page to the desired context.
    *
@@ -2709,6 +2730,12 @@ class WorkerTransport {
     });
   }
 
+  getPageXfa(pageIndex) {
+    return this.messageHandler.sendWithPromise("GetPageXfa", {
+      pageIndex,
+    });
+  }
+
   getOutline() {
     return this.messageHandler.sendWithPromise("GetOutline", null);
   }