[api-minor] Move addLinkAttributes and LinkTarget into the viewer

As part of the changes/improvement in PR 14092, we're no longer using the `addLinkAttributes` directly in e.g. the AnnotationLayer-code.
Given that the helper function is now *only* used in the viewer, hence it no longer seems necessary to expose it through the official API.

*Please note:* It seems somewhat unlikely that third-party users were relying *directly* on the helper function, which is why it's not being exported as part of the viewer components. (If necessary, we can always change this later on.)

web/app.js

@@ -46,7 +46,6 @@ import {
   GlobalWorkerOptions,
   InvalidPDFException,
   isPdfFile,
-  LinkTarget,
   loadScript,
   MissingPDFException,
   OPS,
@@ -57,6 +56,7 @@ import {
   version,
 } from "pdfjs-lib";
 import { CursorTool, PDFCursorTools } from "./pdf_cursor_tools.js";
+import { LinkTarget, PDFLinkService } from "./pdf_link_service.js";
 import { OverlayManager } from "./overlay_manager.js";
 import { PasswordPrompt } from "./password_prompt.js";
 import { PDFAttachmentViewer } from "./pdf_attachment_viewer.js";
@@ -65,7 +65,6 @@ import { PDFFindBar } from "./pdf_find_bar.js";
 import { PDFFindController } from "./pdf_find_controller.js";
 import { PDFHistory } from "./pdf_history.js";
 import { PDFLayerViewer } from "./pdf_layer_viewer.js";
-import { PDFLinkService } from "./pdf_link_service.js";
 import { PDFOutlineViewer } from "./pdf_outline_viewer.js";
 import { PDFPresentationMode } from "./pdf_presentation_mode.js";
 import { PDFRenderingQueue } from "./pdf_rendering_queue.js";

web/pdf_link_service.js

@@ -16,8 +16,73 @@
 /** @typedef {import("./event_utils").EventBus} EventBus */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 
-import { addLinkAttributes, LinkTarget } from "pdfjs-lib";
 import { parseQueryString } from "./ui_utils.js";
+import { removeNullCharacters } from "pdfjs-lib";
+
+const DEFAULT_LINK_REL = "noopener noreferrer nofollow";
+
+const LinkTarget = {
+  NONE: 0, // Default value.
+  SELF: 1,
+  BLANK: 2,
+  PARENT: 3,
+  TOP: 4,
+};
+
+/**
+ * @typedef ExternalLinkParameters
+ * @typedef {Object} ExternalLinkParameters
+ * @property {string} url - An absolute URL.
+ * @property {LinkTarget} [target] - The link target. The default value is
+ *   `LinkTarget.NONE`.
+ * @property {string} [rel] - The link relationship. The default value is
+ *   `DEFAULT_LINK_REL`.
+ * @property {boolean} [enabled] - Whether the link should be enabled. The
+ *   default value is true.
+ */
+
+/**
+ * Adds various attributes (href, title, target, rel) to hyperlinks.
+ * @param {HTMLAnchorElement} link - The link element.
+ * @param {ExternalLinkParameters} params
+ */
+function addLinkAttributes(link, { url, target, rel, enabled = true } = {}) {
+  if (!url || typeof url !== "string") {
+    throw new Error('A valid "url" parameter must provided.');
+  }
+
+  const urlNullRemoved = removeNullCharacters(url);
+  if (enabled) {
+    link.href = link.title = urlNullRemoved;
+  } else {
+    link.href = "";
+    link.title = `Disabled: ${urlNullRemoved}`;
+    link.onclick = () => {
+      return false;
+    };
+  }
+
+  let targetStr = ""; // LinkTarget.NONE
+  switch (target) {
+    case LinkTarget.NONE:
+      break;
+    case LinkTarget.SELF:
+      targetStr = "_self";
+      break;
+    case LinkTarget.BLANK:
+      targetStr = "_blank";
+      break;
+    case LinkTarget.PARENT:
+      targetStr = "_parent";
+      break;
+    case LinkTarget.TOP:
+      targetStr = "_top";
+      break;
+  }
+  link.target = targetStr;
+
+  link.rel = typeof rel === "string" ? rel : DEFAULT_LINK_REL;
+}
 
 /**
  * @typedef {Object} PDFLinkServiceOptions
@@ -230,7 +295,7 @@ class PDFLinkService {
   }
 
   /**
-   * Wrapper around the `addLinkAttributes`-function in the API.
+   * Wrapper around the `addLinkAttributes` helper function.
    * @param {HTMLAnchorElement} link
    * @param {string} url
    * @param {boolean} [newWindow]
@@ -634,4 +699,4 @@ class SimpleLinkService {
   }
 }
 
-export { PDFLinkService, SimpleLinkService };
+export { LinkTarget, PDFLinkService, SimpleLinkService };

web/pdf_viewer.component.js

@@ -19,7 +19,11 @@ import {
   DefaultTextLayerFactory,
   DefaultXfaLayerFactory,
 } from "./default_factory.js";
-import { PDFLinkService, SimpleLinkService } from "./pdf_link_service.js";
+import {
+  LinkTarget,
+  PDFLinkService,
+  SimpleLinkService,
+} from "./pdf_link_service.js";
 import { PDFSinglePageViewer, PDFViewer } from "./pdf_viewer.js";
 import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
 import { DownloadManager } from "./download_manager.js";
@@ -49,6 +53,7 @@ export {
   DownloadManager,
   EventBus,
   GenericL10n,
+  LinkTarget,
   NullL10n,
   PDFFindController,
   PDFHistory,