Replace the IPDFPrintServiceFactory interface with an abstract BasePrintServiceFactory class

This should help reduce the maintenance burden of the code, since you no longer need to remember to update separate code when touching the different `PDFPrintServiceFactory` classes.

web/app.js

@@ -2456,10 +2456,7 @@ const PDFViewerApplication = {
 };
 
 initCom(PDFViewerApplication);
-
-if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
-  PDFPrintServiceFactory.initGlobals(PDFViewerApplication);
-}
+PDFPrintServiceFactory.initGlobals(PDFViewerApplication);
 
 if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
   const HOSTED_VIEWER_ORIGINS = new Set([

web/firefox_print_service.js

@@ -19,7 +19,10 @@ import {
   RenderingCancelledException,
   shadow,
 } from "pdfjs-lib";
-import { getXfaHtmlForPrinting } from "./print_utils.js";
+import {
+  BasePrintServiceFactory,
+  getXfaHtmlForPrinting,
+} from "./print_utils.js";
 
 // Creates a placeholder with div and canvas with right size for the page.
 function composePage(
@@ -194,10 +197,7 @@ class FirefoxPrintService {
   }
 }
 
-/**
- * @implements {IPDFPrintServiceFactory}
- */
-class PDFPrintServiceFactory {
+class PDFPrintServiceFactory extends BasePrintServiceFactory {
   static get supportsPrinting() {
     const canvas = document.createElement("canvas");
     return shadow(this, "supportsPrinting", "mozPrintCallback" in canvas);

web/interfaces.js

@@ -71,19 +71,4 @@ class IDownloadManager {
   download(data, url, filename) {}
 }
 
-/**
- * @interface
- */
-class IPDFPrintServiceFactory {
-  static initGlobals() {}
-
-  static get supportsPrinting() {
-    return false;
-  }
-
-  static createPrintService() {
-    throw new Error("Not implemented: createPrintService");
-  }
-}
-
-export { IDownloadManager, IPDFPrintServiceFactory, IRenderableView };
+export { IDownloadManager, IRenderableView };

web/pdf_print_service.js

@@ -13,16 +13,16 @@
  * limitations under the License.
  */
 
-// eslint-disable-next-line max-len
-/** @typedef {import("./interfaces.js").IPDFPrintServiceFactory} IPDFPrintServiceFactory */
-
 import {
   AnnotationMode,
   PixelsPerInch,
   RenderingCancelledException,
   shadow,
 } from "pdfjs-lib";
-import { getXfaHtmlForPrinting } from "./print_utils.js";
+import {
+  BasePrintServiceFactory,
+  getXfaHtmlForPrinting,
+} from "./print_utils.js";
 
 let activeService = null;
 let dialog = null;
@@ -371,10 +371,7 @@ function ensureOverlay() {
   return overlayPromise;
 }
 
-/**
- * @implements {IPDFPrintServiceFactory}
- */
-class PDFPrintServiceFactory {
+class PDFPrintServiceFactory extends BasePrintServiceFactory {
   static initGlobals(app) {
     viewerApp = app;
   }

web/print_utils.js

@@ -17,6 +17,24 @@ import { getXfaPageViewport, PixelsPerInch } from "pdfjs-lib";
 import { SimpleLinkService } from "./pdf_link_service.js";
 import { XfaLayerBuilder } from "./xfa_layer_builder.js";
 
+class BasePrintServiceFactory {
+  constructor() {
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
+      throw new Error("Cannot initialize BasePrintServiceFactory.");
+    }
+  }
+
+  static initGlobals(app) {}
+
+  static get supportsPrinting() {
+    throw new Error("Not implemented: supportsPrinting");
+  }
+
+  static createPrintService(params) {
+    throw new Error("Not implemented: createPrintService");
+  }
+}
+
 function getXfaHtmlForPrinting(printContainer, pdfDocument) {
   const xfaHtml = pdfDocument.allXfaHtml;
   const linkService = new SimpleLinkService();
@@ -40,4 +58,4 @@ function getXfaHtmlForPrinting(printContainer, pdfDocument) {
   }
 }
 
-export { getXfaHtmlForPrinting };
+export { BasePrintServiceFactory, getXfaHtmlForPrinting };