[api-minor] Introduce a PrintAnnotationStorage with *frozen* serializable data

Given that printing is triggered *synchronously* in browsers, it's thus possible for scripting (in PDF documents) to modify the Annotation-data while printing is currently ongoing.
To work-around that we add a new printing-specific `AnnotationStorage`, where the serializable data is *frozen* upon initialization, which the viewer can thus create/utilize during printing.

web/app.js

@@ -254,6 +254,7 @@ const PDFViewerApplication = {
   _wheelUnusedTicks: 0,
   _idleCallbacks: new Set(),
   _PDFBug: null,
+  _printAnnotationStoragePromise: null,
 
   // Called once when the document is loaded.
   async initialize(appConfig) {
@@ -1790,9 +1791,14 @@ const PDFViewerApplication = {
   },
 
   beforePrint() {
-    // Given that the "beforeprint" browser event is synchronous, we
-    // unfortunately cannot await the scripting event dispatching here.
-    this.pdfScriptingManager.dispatchWillPrint();
+    this._printAnnotationStoragePromise = this.pdfScriptingManager
+      .dispatchWillPrint()
+      .catch(() => {
+        /* Avoid breaking printing; ignoring errors. */
+      })
+      .then(() => {
+        return this.pdfDocument?.annotationStorage.print;
+      });
 
     if (this.printService) {
       // There is no way to suppress beforePrint/afterPrint events,
@@ -1830,6 +1836,7 @@ const PDFViewerApplication = {
       printContainer,
       printResolution,
       optionalContentConfigPromise,
+      this._printAnnotationStoragePromise,
       this.l10n
     );
     this.printService = printService;
@@ -1843,9 +1850,12 @@ const PDFViewerApplication = {
   },
 
   afterPrint() {
-    // Given that the "afterprint" browser event is synchronous, we
-    // unfortunately cannot await the scripting event dispatching here.
-    this.pdfScriptingManager.dispatchDidPrint();
+    if (this._printAnnotationStoragePromise) {
+      this._printAnnotationStoragePromise.then(() => {
+        this.pdfScriptingManager.dispatchDidPrint();
+      });
+      this._printAnnotationStoragePromise = null;
+    }
 
     if (this.printService) {
       this.printService.destroy();

web/firefox_print_service.js

@@ -29,7 +29,8 @@ function composePage(
   size,
   printContainer,
   printResolution,
-  optionalContentConfigPromise
+  optionalContentConfigPromise,
+  printAnnotationStoragePromise
 ) {
   const canvas = document.createElement("canvas");
 
@@ -61,9 +62,12 @@ function composePage(
     ctx.restore();
 
     let thisRenderTask = null;
-    pdfDocument
-      .getPage(pageNumber)
-      .then(function (pdfPage) {
+
+    Promise.all([
+      pdfDocument.getPage(pageNumber),
+      printAnnotationStoragePromise,
+    ])
+      .then(function ([pdfPage, printAnnotationStorage]) {
         if (currentRenderTask) {
           currentRenderTask.cancel();
           currentRenderTask = null;
@@ -75,6 +79,7 @@ function composePage(
           intent: "print",
           annotationMode: AnnotationMode.ENABLE_STORAGE,
           optionalContentConfigPromise,
+          printAnnotationStorage,
         };
         currentRenderTask = thisRenderTask = pdfPage.render(renderContext);
         return thisRenderTask.promise;
@@ -114,7 +119,8 @@ function FirefoxPrintService(
   pagesOverview,
   printContainer,
   printResolution,
-  optionalContentConfigPromise = null
+  optionalContentConfigPromise = null,
+  printAnnotationStoragePromise = null
 ) {
   this.pdfDocument = pdfDocument;
   this.pagesOverview = pagesOverview;
@@ -122,6 +128,8 @@ function FirefoxPrintService(
   this._printResolution = printResolution || 150;
   this._optionalContentConfigPromise =
     optionalContentConfigPromise || pdfDocument.getOptionalContentConfig();
+  this._optionalContentConfigPromise =
+    printAnnotationStoragePromise || Promise.resolve();
 }
 
 FirefoxPrintService.prototype = {
@@ -132,6 +140,7 @@ FirefoxPrintService.prototype = {
       printContainer,
       _printResolution,
       _optionalContentConfigPromise,
+      _printAnnotationStoragePromise,
     } = this;
 
     const body = document.querySelector("body");
@@ -149,7 +158,8 @@ FirefoxPrintService.prototype = {
         pagesOverview[i],
         printContainer,
         _printResolution,
-        _optionalContentConfigPromise
+        _optionalContentConfigPromise,
+        _printAnnotationStoragePromise
       );
     }
   },
@@ -175,14 +185,16 @@ PDFPrintServiceFactory.instance = {
     pagesOverview,
     printContainer,
     printResolution,
-    optionalContentConfigPromise
+    optionalContentConfigPromise,
+    printAnnotationStoragePromise
   ) {
     return new FirefoxPrintService(
       pdfDocument,
       pagesOverview,
       printContainer,
       printResolution,
-      optionalContentConfigPromise
+      optionalContentConfigPromise,
+      printAnnotationStoragePromise
     );
   },
 };

web/pdf_print_service.js

@@ -29,7 +29,8 @@ function renderPage(
   pageNumber,
   size,
   printResolution,
-  optionalContentConfigPromise
+  optionalContentConfigPromise,
+  printAnnotationStoragePromise
 ) {
   const scratchCanvas = activeService.scratchCanvas;
 
@@ -44,7 +45,10 @@ function renderPage(
   ctx.fillRect(0, 0, scratchCanvas.width, scratchCanvas.height);
   ctx.restore();
 
-  return pdfDocument.getPage(pageNumber).then(function (pdfPage) {
+  return Promise.all([
+    pdfDocument.getPage(pageNumber),
+    printAnnotationStoragePromise,
+  ]).then(function ([pdfPage, printAnnotationStorage]) {
     const renderContext = {
       canvasContext: ctx,
       transform: [PRINT_UNITS, 0, 0, PRINT_UNITS, 0, 0],
@@ -52,6 +56,7 @@ function renderPage(
       intent: "print",
       annotationMode: AnnotationMode.ENABLE_STORAGE,
       optionalContentConfigPromise,
+      printAnnotationStorage,
     };
     return pdfPage.render(renderContext).promise;
   });
@@ -63,6 +68,7 @@ function PDFPrintService(
   printContainer,
   printResolution,
   optionalContentConfigPromise = null,
+  printAnnotationStoragePromise = null,
   l10n
 ) {
   this.pdfDocument = pdfDocument;
@@ -71,6 +77,8 @@ function PDFPrintService(
   this._printResolution = printResolution || 150;
   this._optionalContentConfigPromise =
     optionalContentConfigPromise || pdfDocument.getOptionalContentConfig();
+  this._printAnnotationStoragePromise =
+    printAnnotationStoragePromise || Promise.resolve();
   this.l10n = l10n;
   this.currentPage = -1;
   // The temporary canvas where renderPage paints one page at a time.
@@ -160,7 +168,8 @@ PDFPrintService.prototype = {
         /* pageNumber = */ index + 1,
         this.pagesOverview[index],
         this._printResolution,
-        this._optionalContentConfigPromise
+        this._optionalContentConfigPromise,
+        this._printAnnotationStoragePromise
       )
         .then(this.useRenderedPage.bind(this))
         .then(function () {
@@ -359,6 +368,7 @@ PDFPrintServiceFactory.instance = {
     printContainer,
     printResolution,
     optionalContentConfigPromise,
+    printAnnotationStoragePromise,
     l10n
   ) {
     if (activeService) {
@@ -370,6 +380,7 @@ PDFPrintServiceFactory.instance = {
       printContainer,
       printResolution,
       optionalContentConfigPromise,
+      printAnnotationStoragePromise,
       l10n
     );
     return activeService;