Avoid to have the text layer mismatching the rendered text with mismatching locales (bug 1869001)

The system locale (used in OffscreenCanvas) can be different from the one guessed by Fluent,
consequently, in order to avoid any mismatch, we just use an attached canvas element.
The original issue can easily be reproduced locally in adding a lang="ja" in viewer.html
(or with an other language for Japanese users).

web/app.js

@@ -441,7 +441,6 @@ const PDFViewerApplication = {
       annotationEditorHighlightColors: AppOptions.get("highlightEditorColors"),
       imageResourcesPath: AppOptions.get("imageResourcesPath"),
       enablePrintAutoRotate: AppOptions.get("enablePrintAutoRotate"),
-      isOffscreenCanvasSupported,
       maxCanvasPixels: AppOptions.get("maxCanvasPixels"),
       enablePermissions: AppOptions.get("enablePermissions"),
       pageColors,

web/pdf_page_view.js

@@ -72,8 +72,6 @@ import { XfaLayerBuilder } from "./xfa_layer_builder.js";
  *   The default value is `AnnotationMode.ENABLE_FORMS`.
  * @property {string} [imageResourcesPath] - Path for image resources, mainly
  *   for annotation icons. Include trailing slash.
- * @property {boolean} [isOffscreenCanvasSupported] - Allows to use an
- *   OffscreenCanvas if needed.
  * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
  *   total pixels, i.e. width * height. Use `-1` for no limit, or `0` for
  *   CSS-only zooming. The default value is 4096 * 4096 (16 mega-pixels).
@@ -154,8 +152,6 @@ class PDFPageView {
     this.#annotationMode =
       options.annotationMode ?? AnnotationMode.ENABLE_FORMS;
     this.imageResourcesPath = options.imageResourcesPath || "";
-    this.isOffscreenCanvasSupported =
-      options.isOffscreenCanvasSupported ?? true;
     this.maxCanvasPixels = options.maxCanvasPixels ?? MAX_CANVAS_PIXELS;
     this.pageColors = options.pageColors || null;
 
@@ -879,7 +875,6 @@ class PDFPageView {
       this.textLayer = new TextLayerBuilder({
         highlighter: this._textHighlighter,
         accessibilityManager: this._accessibilityManager,
-        isOffscreenCanvasSupported: this.isOffscreenCanvasSupported,
         enablePermissions:
           this.#textLayerMode === TextLayerMode.ENABLE_PERMISSIONS,
       });

web/pdf_viewer.css

@@ -46,7 +46,8 @@
   transform: rotate(270deg) translateX(-100%);
 }
 
-#hiddenCopyElement {
+#hiddenCopyElement,
+.hiddenCanvasElement {
   position: absolute;
   top: 0;
   left: 0;

web/pdf_viewer.js

@@ -115,8 +115,6 @@ function isValidAnnotationEditorMode(mode) {
  *   mainly for annotation icons. Include trailing slash.
  * @property {boolean} [enablePrintAutoRotate] - Enables automatic rotation of
  *   landscape pages upon printing. The default is `false`.
- * @property {boolean} [isOffscreenCanvasSupported] - Allows to use an
- *   OffscreenCanvas if needed.
  * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
  *   total pixels, i.e. width * height. Use `-1` for no limit, or `0` for
  *   CSS-only zooming. The default value is 4096 * 4096 (16 mega-pixels).
@@ -287,8 +285,6 @@ class PDFViewer {
     if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
       this.removePageBorders = options.removePageBorders || false;
     }
-    this.isOffscreenCanvasSupported =
-      options.isOffscreenCanvasSupported ?? true;
     this.maxCanvasPixels = options.maxCanvasPixels;
     this.l10n = options.l10n || NullL10n;
     this.#enablePermissions = options.enablePermissions || false;
@@ -919,7 +915,6 @@ class PDFViewer {
             textLayerMode,
             annotationMode,
             imageResourcesPath: this.imageResourcesPath,
-            isOffscreenCanvasSupported: this.isOffscreenCanvasSupported,
             maxCanvasPixels: this.maxCanvasPixels,
             pageColors: this.pageColors,
             l10n: this.l10n,

web/text_layer_builder.js

@@ -28,8 +28,6 @@ import { removeNullCharacters } from "./ui_utils.js";
  * @property {TextHighlighter} highlighter - Optional object that will handle
  *   highlighting text from the find controller.
  * @property {TextAccessibilityManager} [accessibilityManager]
- * @property {boolean} [isOffscreenCanvasSupported] - Allows to use an
- *   OffscreenCanvas if needed.
  */
 
 /**
@@ -49,7 +47,6 @@ class TextLayerBuilder {
   constructor({
     highlighter = null,
     accessibilityManager = null,
-    isOffscreenCanvasSupported = true,
     enablePermissions = false,
   }) {
     this.textContentItemsStr = [];
@@ -59,7 +56,6 @@ class TextLayerBuilder {
     this.textLayerRenderTask = null;
     this.highlighter = highlighter;
     this.accessibilityManager = accessibilityManager;
-    this.isOffscreenCanvasSupported = isOffscreenCanvasSupported;
     this.#enablePermissions = enablePermissions === true;
 
     /**
@@ -107,7 +103,6 @@ class TextLayerBuilder {
           viewport,
           textDivs: this.textDivs,
           textDivProperties: this.textDivProperties,
-          isOffscreenCanvasSupported: this.isOffscreenCanvasSupported,
           mustRescale,
           mustRotate,
         });
@@ -129,7 +124,6 @@ class TextLayerBuilder {
       textDivs: this.textDivs,
       textDivProperties: this.textDivProperties,
       textContentItemsStr: this.textContentItemsStr,
-      isOffscreenCanvasSupported: this.isOffscreenCanvasSupported,
     });
 
     await this.textLayerRenderTask.promise;