Bug 1415408 - send 'a11y-consumers-changed' notifcation whenever accessibility services consumers change. r=surkov

MozReview-Commit-ID: 2V4X4AO3JAT

accessible/base/nsAccessibilityService.cpp

@@ -25,6 +25,7 @@
 #include "nsAttrName.h"
 #include "nsEventShell.h"
 #include "nsIURI.h"
+#include "nsTextFormatter.h"
 #include "OuterDocAccessible.h"
 #include "Role.h"
 #ifdef MOZ_ACCESSIBILITY_ATK
@@ -1397,8 +1398,7 @@ nsAccessibilityService::Shutdown()
   // if someone will try to operate with it.
 
   MOZ_ASSERT(gConsumers, "Accessibility was shutdown already");
-
-  gConsumers = 0;
+  UnsetConsumers(eXPCOM | eMainProcess | ePlatformAPI);
 
   // Remove observers.
   nsCOMPtr<nsIObserverService> observerService =
@@ -1856,6 +1856,47 @@ nsAccessibilityService::CreateAccessibleForXULTree(nsIContent* aContent,
 }
 #endif
 
+void
+nsAccessibilityService::SetConsumers(uint32_t aConsumers) {
+  if (gConsumers & aConsumers) {
+    return;
+  }
+
+  gConsumers |= aConsumers;
+  NotifyOfConsumersChange();
+}
+
+void
+nsAccessibilityService::UnsetConsumers(uint32_t aConsumers) {
+  if (!(gConsumers & aConsumers)) {
+    return;
+  }
+
+  gConsumers &= ~aConsumers;
+  NotifyOfConsumersChange();
+}
+
+void
+nsAccessibilityService::NotifyOfConsumersChange()
+{
+  nsCOMPtr<nsIObserverService> observerService =
+    mozilla::services::GetObserverService();
+
+  if (!observerService) {
+    return;
+  }
+
+  const char16_t* kJSONFmt =
+    u"{ \"XPCOM\": %s, \"MainProcess\": %s, \"PlatformAPI\": %s }";
+  nsString json;
+  nsTextFormatter::ssprintf(json, kJSONFmt,
+    gConsumers & eXPCOM ? "true" : "false",
+    gConsumers & eMainProcess ? "true" : "false",
+    gConsumers & ePlatformAPI ? "true" : "false");
+  observerService->NotifyObservers(
+    nullptr, "a11y-consumers-changed", json.get());
+}
+
 nsAccessibilityService*
 GetOrCreateAccService(uint32_t aNewConsumer)
 {
@@ -1869,7 +1910,7 @@ GetOrCreateAccService(uint32_t aNewConsumer)
 
   MOZ_ASSERT(nsAccessibilityService::gAccessibilityService,
              "Accessible service is not initialized.");
-  nsAccessibilityService::gConsumers |= aNewConsumer;
+  nsAccessibilityService::gAccessibilityService->SetConsumers(aNewConsumer);
   return nsAccessibilityService::gAccessibilityService;
 }
 
@@ -1887,14 +1928,15 @@ MaybeShutdownAccService(uint32_t aFormerConsumer)
       xpcAccessibilityService::IsInUse() ||
       accService->HasXPCDocuments()) {
     // Still used by XPCOM
-    nsAccessibilityService::gConsumers =
-      (nsAccessibilityService::gConsumers & ~aFormerConsumer) |
-      nsAccessibilityService::eXPCOM;
+    if (aFormerConsumer != nsAccessibilityService::eXPCOM) {
+      // Only unset non-XPCOM consumers.
+      accService->UnsetConsumers(aFormerConsumer);
+    }
     return;
   }
 
   if (nsAccessibilityService::gConsumers & ~aFormerConsumer) {
-    nsAccessibilityService::gConsumers &= ~aFormerConsumer;
+    accService->UnsetConsumers(aFormerConsumer);
   } else {
     accService->Shutdown(); // Will unset all nsAccessibilityService::gConsumers
   }

accessible/base/nsAccessibilityService.h

@@ -304,6 +304,21 @@ private:
     CreateAccessibleByFrameType(nsIFrame* aFrame, nsIContent* aContent,
                                 Accessible* aContext);
 
+  /**
+   * Notify observers about change of the accessibility service's consumers.
+   */
+  void NotifyOfConsumersChange();
+
+  /**
+   * Set accessibility service consumers.
+   */
+  void SetConsumers(uint32_t aConsumers);
+
+  /**
+   * Unset accessibility service consumers.
+   */
+  void UnsetConsumers(uint32_t aConsumers);
+
 #ifdef MOZ_XUL
   /**
    * Create accessible for XUL tree element.

accessible/tests/browser/browser_shutdown_remote_no_reference.js

@@ -25,22 +25,40 @@ add_task(async function() {
     // the a11y service in parent as well.
     let parentA11yInit = initPromise();
     let contentA11yInit = initPromise(browser);
+    let parentConsumersChanged = a11yConsumersChangedPromise();
+    let contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     let accService = Cc["@mozilla.org/accessibilityService;1"].getService(
       Ci.nsIAccessibilityService);
     ok(accService, "Service initialized in parent");
     await Promise.all([parentA11yInit, contentA11yInit]);
+    await parentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: true, MainProcess: false, PlatformAPI: false
+    }, "Accessibility service consumers in parent are correct."));
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: false, MainProcess: true, PlatformAPI: false
+    }, "Accessibility service consumers in content are correct."));
 
     info("Removing a service in parent and waiting for service to be shut " +
       "down in content");
     // Remove a11y service reference in the main process.
     let parentA11yShutdown = shutdownPromise();
     let contentA11yShutdown = shutdownPromise(browser);
+    parentConsumersChanged = a11yConsumersChangedPromise();
+    contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     accService = null;
     ok(!accService, "Service is removed in parent");
     // Force garbage collection that should trigger shutdown in both main and
     // content process.
     forceGC();
     await Promise.all([parentA11yShutdown, contentA11yShutdown]);
+    await parentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: false, MainProcess: false, PlatformAPI: false
+    }, "Accessibility service consumers are correct."));
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: false, MainProcess: false, PlatformAPI: false
+    }, "Accessibility service consumers are correct."));
   });
 
   // Unsetting e10s related preferences.

accessible/tests/browser/browser_shutdown_remote_own_reference.js

@@ -25,22 +25,34 @@ add_task(async function() {
     // the a11y service in parent as well.
     let parentA11yInit = initPromise();
     let contentA11yInit = initPromise(browser);
+    let contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     let accService = Cc["@mozilla.org/accessibilityService;1"].getService(
       Ci.nsIAccessibilityService);
     ok(accService, "Service initialized in parent");
     await Promise.all([parentA11yInit, contentA11yInit]);
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: false, MainProcess: true, PlatformAPI: false
+    }, "Accessibility service consumers in content are correct."));
 
     info("Adding additional reference to accessibility service in content " +
       "process");
+    contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     // Add a new reference to the a11y service inside the content process.
     loadFrameScripts(browser, `let accService = Components.classes[
       '@mozilla.org/accessibilityService;1'].getService(
         Components.interfaces.nsIAccessibilityService);`);
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: true, MainProcess: true, PlatformAPI: false
+    }, "Accessibility service consumers in content are correct."));
 
     info("Shutting down a service in parent and making sure the one in " +
       "content stays alive");
     let contentCanShutdown = false;
     let parentA11yShutdown = shutdownPromise();
+    contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     // This promise will resolve only if contentCanShutdown flag is set to true.
     // If 'a11y-init-or-shutdown' event with '0' flag (in content) comes before
     // it can be shut down, the promise will reject.
@@ -57,6 +69,9 @@ add_task(async function() {
     forceGC();
     loadFrameScripts(browser, `Components.utils.forceGC();`);
     await parentA11yShutdown;
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: true, MainProcess: false, PlatformAPI: false
+    }, "Accessibility service consumers in content are correct."));
 
     // Have some breathing room between a11y service shutdowns.
     await new Promise(resolve => executeSoon(resolve));
@@ -64,10 +79,15 @@ add_task(async function() {
     info("Removing a service in content");
     // Now allow a11y service to shutdown in content.
     contentCanShutdown = true;
+    contentConsumersChanged =
+      ContentTask.spawn(browser, {}, a11yConsumersChangedPromise);
     // Remove last reference to a11y service in content and force garbage
     // collection that should trigger shutdown.
     loadFrameScripts(browser, `accService = null; Components.utils.forceGC();`);
     await contentA11yShutdown;
+    await contentConsumersChanged.then(data => Assert.deepEqual(data, {
+      XPCOM: false, MainProcess: false, PlatformAPI: false
+    }, "Accessibility service consumers in content are correct."));
 
     // Unsetting e10s related preferences.
     await unsetE10sPrefs();

accessible/tests/browser/head.js

@@ -37,6 +37,20 @@ Services.scriptloader.loadSubScript(
   "chrome://mochitests/content/browser/accessible/tests/browser/shared-head.js",
   this);
 
+/**
+ * Returns a promise that resolves when 'a11y-consumers-changed' event is fired.
+ * @return {Promise} event promise evaluating to event's data
+ */
+function a11yConsumersChangedPromise() {
+  return new Promise(resolve => {
+    let observe = (subject, topic, data) => {
+      Services.obs.removeObserver(observe, "a11y-consumers-changed");
+      resolve(JSON.parse(data));
+    };
+    Services.obs.addObserver(observe, "a11y-consumers-changed");
+  });
+}
+
 /**
  * Returns a promise that resolves when 'a11y-init-or-shutdown' event is fired.
  * @return {Promise} event promise evaluating to event's data