Bug 1948481 - Correctly set the observer used to be aware of the changes in the signature storage for PDF.js r=marco

Differential Revision: https://phabricator.services.mozilla.com/D238375

Author: calixteman

toolkit/components/pdfjs/content/PdfjsParent.sys.mjs

@@ -84,6 +84,13 @@ export class PdfjsParent extends JSWindowActorParent {
 
   didDestroy() {
     this._removeEventListener();
+    if (this.#signatureStorageChangedObserver) {
+      Services.obs.removeObserver(
+        this.#signatureStorageChangedObserver,
+        PDFJS_SIGNATURE_STORAGE_CHANGED_TOPIC
+      );
+      this.#signatureStorageChangedObserver = null;
+    }
   }
 
   receiveMessage(aMsg) {
@@ -148,29 +155,27 @@ export class PdfjsParent extends JSWindowActorParent {
   async #getSignatures() {
     if (!this.#signatureStorageChangedObserver) {
       const self = this;
-      this.#signatureStorageChangedObserver = Services.obs.addObserver(
-        {
-          observe(aSubject, aTopic) {
-            if (
-              aTopic === PDFJS_SIGNATURE_STORAGE_CHANGED_TOPIC &&
-              // No need to send an event to the viewer which triggered the
-              // change because it already knows about it.
-              aSubject !== self &&
-              !Cu.isInAutomation
-            ) {
-              // The child will dispatch an event in the pdf.js window.
-              // This way the viewer is able to update the UI (add/remove some
-              // signatures).
-              self.sendAsyncMessage("PDFJS:Child:handleEvent", {
-                type: "storedSignaturesChanged",
-                detail: null,
-              });
-            }
-          },
-          QueryInterface: ChromeUtils.generateQI([Ci.nsISupportsWeakReference]),
+      this.#signatureStorageChangedObserver = {
+        observe(aSubject, aTopic) {
+          if (
+            aTopic === PDFJS_SIGNATURE_STORAGE_CHANGED_TOPIC &&
+            // No need to send an event to the viewer which triggered the
+            // change because it already knows about it.
+            (aSubject !== self || Cu.isInAutomation)
+          ) {
+            // The child will dispatch an event in the pdf.js window.
+            // This way the viewer is able to update the UI (add/remove some
+            // signatures).
+            self.sendAsyncMessage("PDFJS:Child:handleEvent", {
+              type: "storedSignaturesChanged",
+              detail: null,
+            });
+          }
         },
-        PDFJS_SIGNATURE_STORAGE_CHANGED_TOPIC,
-        true
+      };
+      Services.obs.addObserver(
+        this.#signatureStorageChangedObserver,
+        PDFJS_SIGNATURE_STORAGE_CHANGED_TOPIC
       );
     }
 

toolkit/components/pdfjs/test/browser_pdfjs_signature_storage.js

@@ -15,6 +15,13 @@ add_task(async function test_js_signature_storage() {
       );
 
       await SpecialPowers.spawn(browser, [], async () => {
+        function getStoredSignaturesChangedPromise() {
+          const { promise, resolve } = Promise.withResolvers();
+          content.addEventListener("storedSignaturesChanged", resolve, {
+            once: true,
+          });
+          return promise;
+        }
         const HANDLE_SIGNATURE = "PDFJS:Parent:handleSignature";
 
         const actor = content.windowGlobalChild.getActor("Pdfjs");
@@ -23,11 +30,13 @@ add_task(async function test_js_signature_storage() {
         });
         is(all.length, 0, "No signature should be present");
 
+        let promise = getStoredSignaturesChangedPromise();
         const uuid = await actor.sendQuery(HANDLE_SIGNATURE, {
           action: "create",
           description: "test",
           signatureData: "1234",
         });
+        await promise;
 
         all = await actor.sendQuery(HANDLE_SIGNATURE, {
           action: "get",
@@ -37,10 +46,12 @@ add_task(async function test_js_signature_storage() {
         is(all[0].description, "test", "Must have the correct description");
         is(all[0].signatureData, "1234", "Must have the correct signatureData");
 
+        promise = getStoredSignaturesChangedPromise();
         await actor.sendQuery(HANDLE_SIGNATURE, {
           action: "delete",
           uuid,
         });
+        await promise;
 
         all = await actor.sendQuery(HANDLE_SIGNATURE, {
           action: "get",