Re-factor how the compatibilityParams, in the viewer, are handled

Previously we'd simply export this directly from `web/app_options.js`, which meant that it'd be technically possible to *accidentally* modify the `compatibilityParams` Object when accessing it.
To avoid this we instead introduce a new `AppOptions`-method that is used to lookup data in `compatibilityParams`, which means that we no longer need to export this Object.

Based on these changes, it's now possible to simplify some existing code in `AppOptions` by taking full advantage of the nullish coalescing (`??`) operator.

web/app_options.js

@@ -438,16 +438,17 @@ class AppOptions {
     throw new Error("Cannot initialize AppOptions.");
   }
 
+  static getCompat(name) {
+    return compatibilityParams[name] ?? undefined;
+  }
+
   static get(name) {
-    const userOption = userOptions[name];
-    if (userOption !== undefined) {
-      return userOption;
-    }
-    const defaultOption = defaultOptions[name];
-    if (defaultOption !== undefined) {
-      return compatibilityParams[name] ?? defaultOption.value;
-    }
-    return undefined;
+    return (
+      userOptions[name] ??
+      compatibilityParams[name] ??
+      defaultOptions[name]?.value ??
+      undefined
+    );
   }
 
   static getAll(kind = null, defaultOnly = false) {
@@ -458,16 +459,9 @@ class AppOptions {
       if (kind && !(kind & defaultOption.kind)) {
         continue;
       }
-      if (defaultOnly) {
-        options[name] = defaultOption.value;
-        continue;
-      }
-      const userOption = userOptions[name];
-
-      options[name] =
-        userOption !== undefined
-          ? userOption
-          : compatibilityParams[name] ?? defaultOption.value;
+      options[name] = defaultOnly
+        ? defaultOption.value
+        : userOptions[name] ?? compatibilityParams[name] ?? defaultOption.value;
     }
     return options;
   }
@@ -501,4 +495,4 @@ class AppOptions {
   }
 }
 
-export { AppOptions, compatibilityParams, OptionKind };
+export { AppOptions, OptionKind };

web/pdf_page_view.js

@@ -41,7 +41,7 @@ import {
 } from "./ui_utils.js";
 import { AnnotationEditorLayerBuilder } from "./annotation_editor_layer_builder.js";
 import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
-import { compatibilityParams } from "./app_options.js";
+import { AppOptions } from "./app_options.js";
 import { DrawLayerBuilder } from "./draw_layer_builder.js";
 import { GenericL10n } from "web-null_l10n";
 import { SimpleLinkService } from "./pdf_link_service.js";
@@ -83,8 +83,6 @@ import { XfaLayerBuilder } from "./xfa_layer_builder.js";
  *   the necessary layer-properties.
  */
 
-const MAX_CANVAS_PIXELS = compatibilityParams.maxCanvasPixels || 16777216;
-
 const DEFAULT_LAYER_PROPERTIES =
   typeof PDFJSDev === "undefined" || !PDFJSDev.test("COMPONENTS")
     ? null
@@ -152,7 +150,9 @@ class PDFPageView {
     this.#annotationMode =
       options.annotationMode ?? AnnotationMode.ENABLE_FORMS;
     this.imageResourcesPath = options.imageResourcesPath || "";
-    this.maxCanvasPixels = options.maxCanvasPixels ?? MAX_CANVAS_PIXELS;
+    this.maxCanvasPixels =
+      options.maxCanvasPixels ??
+      (AppOptions.getCompat("maxCanvasPixels") || 16777216);
     this.pageColors = options.pageColors || null;
 
     this.eventBus = options.eventBus;