XFA - Save filled data in the pdf when downloading the file

  - when binding (after parsing) we get a map between some template nodes and some data nodes;
  - so set user data in input handlers in using data node uids in the annotation storage;
  - to save the form, just put the value we have in the storage in the correct data nodes, serialize the xml as a string and then write the string at the end of the pdf using src/core/writer.js;
  - fix few bugs around data bindings.

Author: calixteman

src/core/document.js

@@ -963,6 +963,13 @@ class PDFDocument {
     this.xfaFactory.setFonts(pdfFonts);
   }
 
+  async serializeXfaData(annotationStorage) {
+    if (this.xfaFactory) {
+      return this.xfaFactory.serializeData(annotationStorage);
+    }
+    return null;
+  }
+
   get formInfo() {
     const formInfo = {
       hasFields: false,

src/core/pdf_manager.js

@@ -77,6 +77,10 @@ class BasePdfManager {
     return this.pdfDocument.loadXfaFonts(handler, task);
   }
 
+  serializeXfaData(annotationStorage) {
+    return this.pdfDocument.serializeXfaData(annotationStorage);
+  }
+
   cleanup(manuallyTriggered = false) {
     return this.pdfDocument.cleanup(manuallyTriggered);
   }

src/core/worker.js

@@ -564,28 +564,31 @@ class WorkerMessageHandler {
 
     handler.on(
       "SaveDocument",
-      function ({ numPages, annotationStorage, filename }) {
+      function ({ isPureXfa, numPages, annotationStorage, filename }) {
         pdfManager.requestLoadedStream();
+
         const promises = [
           pdfManager.onLoadedStream(),
           pdfManager.ensureCatalog("acroForm"),
           pdfManager.ensureDoc("xref"),
           pdfManager.ensureDoc("startXRef"),
         ];
 
-        for (let pageIndex = 0; pageIndex < numPages; pageIndex++) {
-          promises.push(
-            pdfManager.getPage(pageIndex).then(function (page) {
-              const task = new WorkerTask(`Save: page ${pageIndex}`);
-              startWorkerTask(task);
-
-              return page
-                .save(handler, task, annotationStorage)
-                .finally(function () {
-                  finishWorkerTask(task);
-                });
-            })
-          );
+        if (isPureXfa) {
+          promises.push(pdfManager.serializeXfaData(annotationStorage));
+        } else {
+          for (let pageIndex = 0; pageIndex < numPages; pageIndex++) {
+            promises.push(
+              pdfManager.getPage(pageIndex).then(function (page) {
+                const task = new WorkerTask(`Save: page ${pageIndex}`);
+                return page
+                  .save(handler, task, annotationStorage)
+                  .finally(function () {
+                    finishWorkerTask(task);
+                  });
+              })
+            );
+          }
         }
 
         return Promise.all(promises).then(function ([
@@ -596,15 +599,23 @@ class WorkerMessageHandler {
           ...refs
         ]) {
           let newRefs = [];
-          for (const ref of refs) {
-            newRefs = ref
-              .filter(x => x !== null)
-              .reduce((a, b) => a.concat(b), newRefs);
-          }
+          let xfaData = null;
+          if (isPureXfa) {
+            xfaData = refs[0];
+            if (!xfaData) {
+              return stream.bytes;
+            }
+          } else {
+            for (const ref of refs) {
+              newRefs = ref
+                .filter(x => x !== null)
+                .reduce((a, b) => a.concat(b), newRefs);
+            }
 
-          if (newRefs.length === 0) {
-            // No new refs so just return the initial bytes
-            return stream.bytes;
+            if (newRefs.length === 0) {
+              // No new refs so just return the initial bytes
+              return stream.bytes;
+            }
           }
 
           const xfa = (acroForm instanceof Dict && acroForm.get("XFA")) || [];
@@ -652,6 +663,7 @@ class WorkerMessageHandler {
             newRefs,
             xref,
             datasetsRef: xfaDatasets,
+            xfaData,
           });
         });
       }

src/core/writer.js

@@ -123,12 +123,7 @@ function computeMD5(filesize, xrefInfo) {
   return bytesToString(calculateMD5(array));
 }
 
-function updateXFA(datasetsRef, newRefs, xref) {
-  if (datasetsRef === null || xref === null) {
-    return;
-  }
-  const datasets = xref.fetchIfRef(datasetsRef);
-  const str = datasets.getString();
+function writeXFADataForAcroform(str, newRefs) {
   const xml = new SimpleXMLParser({ hasAttributes: true }).parseFromString(str);
 
   for (const { xfa } of newRefs) {
@@ -148,20 +143,30 @@ function updateXFA(datasetsRef, newRefs, xref) {
   }
   const buffer = [];
   xml.documentElement.dump(buffer);
-  let updatedXml = buffer.join("");
+  return buffer.join("");
+}
+
+function updateXFA(xfaData, datasetsRef, newRefs, xref) {
+  if (datasetsRef === null || xref === null) {
+    return;
+  }
+  if (xfaData === null) {
+    const datasets = xref.fetchIfRef(datasetsRef);
+    xfaData = writeXFADataForAcroform(datasets.getString(), newRefs);
+  }
 
   const encrypt = xref.encrypt;
   if (encrypt) {
     const transform = encrypt.createCipherTransform(
       datasetsRef.num,
       datasetsRef.gen
     );
-    updatedXml = transform.encryptString(updatedXml);
+    xfaData = transform.encryptString(xfaData);
   }
   const data =
     `${datasetsRef.num} ${datasetsRef.gen} obj\n` +
-    `<< /Type /EmbeddedFile /Length ${updatedXml.length}>>\nstream\n` +
-    updatedXml +
+    `<< /Type /EmbeddedFile /Length ${xfaData.length}>>\nstream\n` +
+    xfaData +
     "\nendstream\nendobj\n";
 
   newRefs.push({ ref: datasetsRef, data });
@@ -173,8 +178,9 @@ function incrementalUpdate({
   newRefs,
   xref = null,
   datasetsRef = null,
+  xfaData = null,
 }) {
-  updateXFA(datasetsRef, newRefs, xref);
+  updateXFA(xfaData, datasetsRef, newRefs, xref);
 
   const newXref = new Dict(null);
   const refForXrefTable = xrefInfo.newRef;

src/core/xfa/bind.js

@@ -29,6 +29,7 @@ import {
   $hasSettableValue,
   $indexOf,
   $insertAt,
+  $isBindable,
   $isDataValue,
   $isDescendent,
   $namespaceId,
@@ -87,12 +88,12 @@ class Binder {
     // data node (through $data property): we'll use it
     // to save form data.
 
+    formNode[$data] = data;
     if (formNode[$hasSettableValue]()) {
       if (data[$isDataValue]()) {
         const value = data[$getDataValue]();
         // TODO: use picture.
         formNode[$setValue](createText(value));
-        formNode[$data] = data;
       } else if (
         formNode instanceof Field &&
         formNode.ui &&
@@ -103,13 +104,11 @@ class Binder {
           .map(child => child[$content].trim())
           .join("\n");
         formNode[$setValue](createText(value));
-        formNode[$data] = data;
       } else if (this._isConsumeData()) {
         warn(`XFA - Nodes haven't the same type.`);
       }
     } else if (!data[$isDataValue]() || this._isMatchTemplate()) {
       this._bindElement(formNode, data);
-      formNode[$data] = data;
     } else {
       warn(`XFA - Nodes haven't the same type.`);
     }
@@ -496,6 +495,12 @@ class Binder {
         continue;
       }
 
+      if (!child[$isBindable]()) {
+        // The node cannot contain some new data so there is nothing
+        // to create in the data node.
+        continue;
+      }
+
       let global = false;
       let picture = null;
       let ref = null;

src/core/xfa/data.js

@@ -0,0 +1,82 @@
+/* Copyright 2021 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  $getAttributes,
+  $getChildren,
+  $nodeName,
+  $setValue,
+  $toString,
+  $uid,
+} from "./xfa_object.js";
+
+class DataHandler {
+  constructor(root, data) {
+    this.data = data;
+    this.dataset = root.datasets || null;
+  }
+
+  serialize(storage) {
+    const stack = [[-1, this.data[$getChildren]()]];
+
+    while (stack.length > 0) {
+      const last = stack[stack.length - 1];
+      const [i, children] = last;
+      if (i + 1 === children.length) {
+        stack.pop();
+        continue;
+      }
+
+      const child = children[++last[0]];
+      const storageEntry = storage.get(child[$uid]);
+      if (storageEntry) {
+        child[$setValue](storageEntry);
+      } else {
+        const attributes = child[$getAttributes]();
+        for (const value of attributes.values()) {
+          const entry = storage.get(value[$uid]);
+          if (entry) {
+            value[$setValue](entry);
+            break;
+          }
+        }
+      }
+
+      const nodes = child[$getChildren]();
+      if (nodes.length > 0) {
+        stack.push([-1, nodes]);
+      }
+    }
+
+    const buf = [
+      `<xfa:datasets xmlns:xfa="http://www.xfa.org/schema/xfa-data/1.0/">`,
+    ];
+    if (this.dataset) {
+      // Dump nodes other than data: they can contains for example
+      // some data for choice lists.
+      for (const child of this.dataset[$getChildren]()) {
+        if (child[$nodeName] !== "data") {
+          child[$toString](buf);
+        }
+      }
+    }
+    this.data[$toString](buf);
+    buf.push("</xfa:datasets>");
+
+    return buf.join("");
+  }
+}
+
+export { DataHandler };

src/core/xfa/factory.js

@@ -15,6 +15,7 @@
 
 import { $globalData, $toHTML } from "./xfa_object.js";
 import { Binder } from "./bind.js";
+import { DataHandler } from "./data.js";
 import { FontFinder } from "./fonts.js";
 import { warn } from "../../shared/util.js";
 import { XFAParser } from "./parser.js";
@@ -23,7 +24,9 @@ class XFAFactory {
   constructor(data) {
     try {
       this.root = new XFAParser().parse(XFAFactory._createDocument(data));
-      this.form = new Binder(this.root).bind();
+      const binder = new Binder(this.root);
+      this.form = binder.bind();
+      this.dataHandler = new DataHandler(this.root, binder.getData());
       this.form[$globalData].template = this.form;
     } catch (e) {
       warn(`XFA - an error occured during parsing and binding: ${e}`);
@@ -70,6 +73,10 @@ class XFAFactory {
     return pages;
   }
 
+  serializeData(storage) {
+    return this.dataHandler.serialize(storage);
+  }
+
   static _createDocument(data) {
     if (!data["/xdp:xdp"]) {
       return data["xdp:xdp"];