[api-minor] Support the Content-Disposition filename in the Firefox PDF Viewer (bug 1694556, PR 9379 follow-up)

As can be seen [in the mozilla-central code](https://searchfox.org/mozilla-central/rev/a6db3bd67367aa9ddd9505690cab09b47e65a762/toolkit/components/pdfjs/content/PdfStreamConverter.jsm#1222-1225), we're already getting the Content-Disposition filename. However, that data isn't passed through to the viewer nor to the `PDFDataTransportStream`-implementation, which explains why it's currently being ignored.

*Please note:* This will also require a small mozilla-central patch, see https://bugzilla.mozilla.org/show_bug.cgi?id=1694556, to forward the necessary data to the viewer.

Author: Snuffleupagus

src/display/api.js

@@ -334,6 +334,7 @@ function getDocument(src) {
               length: params.length,
               initialData: params.initialData,
               progressiveDone: params.progressiveDone,
+              contentDispositionFilename: params.contentDispositionFilename,
               disableRange: params.disableRange,
               disableStream: params.disableStream,
             },
@@ -401,6 +402,8 @@ function _fetchDocument(worker, source, pdfDataRangeTransport, docId) {
     source.length = pdfDataRangeTransport.length;
     source.initialData = pdfDataRangeTransport.initialData;
     source.progressiveDone = pdfDataRangeTransport.progressiveDone;
+    source.contentDispositionFilename =
+      pdfDataRangeTransport.contentDispositionFilename;
   }
   return worker.messageHandler
     .sendWithPromise("GetDocRequest", {
@@ -554,11 +557,18 @@ class PDFDataRangeTransport {
    * @param {number} length
    * @param {Uint8Array} initialData
    * @param {boolean} [progressiveDone]
+   * @param {string} [contentDispositionFilename]
    */
-  constructor(length, initialData, progressiveDone = false) {
+  constructor(
+    length,
+    initialData,
+    progressiveDone = false,
+    contentDispositionFilename = null
+  ) {
     this.length = length;
     this.initialData = initialData;
     this.progressiveDone = progressiveDone;
+    this.contentDispositionFilename = contentDispositionFilename;
 
     this._rangeListeners = [];
     this._progressListeners = [];

src/display/transport_stream.js

@@ -15,6 +15,13 @@
 
 import { assert, createPromiseCapability } from "../shared/util.js";
 
+function validateFilename(filename) {
+  if (typeof filename === "string" && /\.pdf$/i.test(filename)) {
+    return filename;
+  }
+  return null;
+}
+
 /** @implements {IPDFStream} */
 class PDFDataTransportStream {
   constructor(params, pdfDataRangeTransport) {
@@ -25,6 +32,8 @@ class PDFDataTransportStream {
 
     this._queuedChunks = [];
     this._progressiveDone = params.progressiveDone || false;
+    this._contentDispositionFilename =
+      params.contentDispositionFilename || null;
 
     const initialData = params.initialData;
     if (initialData?.length > 0) {
@@ -125,7 +134,8 @@ class PDFDataTransportStream {
     return new PDFDataTransportStreamReader(
       this,
       queuedChunks,
-      this._progressiveDone
+      this._progressiveDone,
+      this._contentDispositionFilename
     );
   }
 
@@ -153,10 +163,15 @@ class PDFDataTransportStream {
 
 /** @implements {IPDFStreamReader} */
 class PDFDataTransportStreamReader {
-  constructor(stream, queuedChunks, progressiveDone = false) {
+  constructor(
+    stream,
+    queuedChunks,
+    progressiveDone = false,
+    contentDispositionFilename = null
+  ) {
     this._stream = stream;
     this._done = progressiveDone || false;
-    this._filename = null;
+    this._filename = validateFilename(contentDispositionFilename);
     this._queuedChunks = queuedChunks || [];
     this._loaded = 0;
     for (const chunk of this._queuedChunks) {

web/app.js

@@ -21,6 +21,7 @@ import {
   EventBus,
   getActiveOrFocusedElement,
   getPDFFileNameFromURL,
+  isPdfFilename,
   isValidRotation,
   isValidScrollMode,
   isValidSpreadMode,
@@ -727,7 +728,11 @@ const PDFViewerApplication = {
       onOpenWithTransport: (url, length, transport) => {
         this.open(url, { length, range: transport });
       },
-      onOpenWithData: data => {
+      onOpenWithData: (data, contentDispositionFilename) => {
+        if (isPdfFilename(contentDispositionFilename)) {
+          this._contentDispositionFilename = contentDispositionFilename;
+        }
+
         this.open(data);
       },
       onOpenWithURL: (url, length, originalUrl) => {
@@ -1744,7 +1749,7 @@ const PDFViewerApplication = {
     }
     this.documentInfo = info;
     this.metadata = metadata;
-    this._contentDispositionFilename = contentDispositionFilename;
+    this._contentDispositionFilename ??= contentDispositionFilename;
     this._contentLength ??= contentLength; // See `getDownloadInfo`-call above.
 
     // Provides some basic debug information

web/firefoxcom.js

@@ -296,7 +296,8 @@ class FirefoxExternalServices extends DefaultExternalServices {
           pdfDataRangeTransport = new FirefoxComDataRangeTransport(
             args.length,
             args.data,
-            args.done
+            args.done,
+            args.filename
           );
 
           callbacks.onOpenWithTransport(
@@ -331,7 +332,7 @@ class FirefoxExternalServices extends DefaultExternalServices {
             callbacks.onError(args.errorCode);
             break;
           }
-          callbacks.onOpenWithData(args.data);
+          callbacks.onOpenWithData(args.data, args.filename);
           break;
       }
     });

web/ui_utils.js

@@ -600,6 +600,10 @@ function noContextMenuHandler(evt) {
   evt.preventDefault();
 }
 
+function isPdfFilename(filename) {
+  return typeof filename === "string" && /\.pdf$/i.test(filename);
+}
+
 function isDataSchema(url) {
   let i = 0;
   const ii = url.length;
@@ -1046,6 +1050,7 @@ export {
   getPageSizeInches,
   getPDFFileNameFromURL,
   getVisibleElements,
+  isPdfFilename,
   isPortraitOrientation,
   isValidRotation,
   isValidScrollMode,