[api-minor] Remove the WebGL implementation

Reasons for the removal include:
 - This functionality was always somewhat experimental and has never been enabled by default, partly because of worries about rendering bugs caused by e.g. bad/outdated graphics drivers.

 - After the initial implementation, in PR 4286 (back in 2014), no additional functionality has been added to the WebGL implementation.

 - The vast majority of all documents do not benefit from WebGL rendering, since only a couple of *specific* features are supported (e.g. some Soft Masks and Patterns).

 - There is, and has always been, *zero* test-coverage for the WebGL implementation.

 - Overall performance, in the PDF.js library, has improved since the experimental WebGL implementation was added.

Rather than shipping unused *and* untested code, it seems reasonable to simply remove the WebGL implementation for now; thanks to version control it's always possible to bring back the code should the need ever arise.

web/app.js

@@ -354,9 +354,6 @@ const PDFViewerApplication = {
     if ("disablehistory" in hashParams) {
       AppOptions.set("disableHistory", hashParams.disablehistory === "true");
     }
-    if ("webgl" in hashParams) {
-      AppOptions.set("enableWebGL", hashParams.webgl === "true");
-    }
     if ("verbosity" in hashParams) {
       AppOptions.set("verbosity", hashParams.verbosity | 0);
     }
@@ -511,7 +508,6 @@ const PDFViewerApplication = {
       findController,
       scriptingManager: pdfScriptingManager,
       renderer: AppOptions.get("renderer"),
-      enableWebGL: AppOptions.get("enableWebGL"),
       l10n: this.l10n,
       textLayerMode: AppOptions.get("textLayerMode"),
       imageResourcesPath: AppOptions.get("imageResourcesPath"),
@@ -1520,8 +1516,7 @@ const PDFViewerApplication = {
     console.log(
       `PDF ${pdfDocument.fingerprint} [${info.PDFFormatVersion} ` +
         `${(info.Producer || "-").trim()} / ${(info.Creator || "-").trim()}] ` +
-        `(PDF.js: ${version || "-"}` +
-        `${this.pdfViewer.enableWebGL ? " [WebGL]" : ""})`
+        `(PDF.js: ${version || "-"})`
     );
 
     let pdfTitle = info?.Title;

web/app_options.js

@@ -70,11 +70,6 @@ const defaultOptions = {
     value: true,
     kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
   },
-  enableWebGL: {
-    /** @type {boolean} */
-    value: false,
-    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
-  },
   externalLinkRel: {
     /** @type {string} */
     value: "noopener noreferrer nofollow",

web/base_viewer.js

@@ -73,8 +73,6 @@ const DEFAULT_CACHE_SIZE = 10;
  * @property {boolean} [enablePrintAutoRotate] - Enables automatic rotation of
  *   landscape pages upon printing. The default is `false`.
  * @property {string} renderer - 'canvas' or 'svg'. The default is 'canvas'.
- * @property {boolean} [enableWebGL] - Enables WebGL accelerated rendering for
- *   some operations. The default value is `false`.
  * @property {boolean} [useOnlyCssZoom] - Enables CSS only zooming. The default
  *   value is `false`.
  * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
@@ -194,7 +192,6 @@ class BaseViewer {
     this.renderInteractiveForms = options.renderInteractiveForms !== false;
     this.enablePrintAutoRotate = options.enablePrintAutoRotate || false;
     this.renderer = options.renderer || RendererType.CANVAS;
-    this.enableWebGL = options.enableWebGL || false;
     this.useOnlyCssZoom = options.useOnlyCssZoom || false;
     this.maxCanvasPixels = options.maxCanvasPixels;
     this.l10n = options.l10n || NullL10n;
@@ -550,7 +547,6 @@ class BaseViewer {
             imageResourcesPath: this.imageResourcesPath,
             renderInteractiveForms: this.renderInteractiveForms,
             renderer: this.renderer,
-            enableWebGL: this.enableWebGL,
             useOnlyCssZoom: this.useOnlyCssZoom,
             maxCanvasPixels: this.maxCanvasPixels,
             l10n: this.l10n,

web/pdf_page_view.js

@@ -55,8 +55,6 @@ import { viewerCompatibilityParams } from "./viewer_compatibility.js";
  * @property {boolean} renderInteractiveForms - Turns on rendering of
  *   interactive form elements. The default value is `true`.
  * @property {string} renderer - 'canvas' or 'svg'. The default is 'canvas'.
- * @property {boolean} [enableWebGL] - Enables WebGL accelerated rendering for
- *   some operations. The default value is `false`.
  * @property {boolean} [useOnlyCssZoom] - Enables CSS only zooming. The default
  *   value is `false`.
  * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
@@ -105,7 +103,6 @@ class PDFPageView {
     this.xfaLayerFactory = options.xfaLayerFactory;
     this.structTreeLayerFactory = options.structTreeLayerFactory;
     this.renderer = options.renderer || RendererType.CANVAS;
-    this.enableWebGL = options.enableWebGL || false;
     this.l10n = options.l10n || NullL10n;
 
     this.paintTask = null;
@@ -728,7 +725,6 @@ class PDFPageView {
       canvasContext: ctx,
       transform,
       viewport: this.viewport,
-      enableWebGL: this.enableWebGL,
       renderInteractiveForms: this.renderInteractiveForms,
       optionalContentConfigPromise: this._optionalContentConfigPromise,
     };