Bug 1198336 - P1: Introduce live region added/removed events. r=Jamie,morgan

VoiceOver pre-caches live region data and does its own deltas to
know what to parts of a subtree changed, and what to announce
based on AXARIAAtomic and AXARIARelevant.

I added a removed event as well. This will help us cache a "live region"
flag in the main process and avoid sync round trips for attributes when not needed.

Differential Revision: https://phabricator.services.mozilla.com/D96291

accessible/base/nsAccessibilityService.h

@@ -498,6 +498,8 @@ static const char kEventTypeNames[][40] = {
     "text value change",                // EVENT_TEXT_VALUE_CHANGE
     "scrolling",                        // EVENT_SCROLLING
     "announcement",                     // EVENT_ANNOUNCEMENT
+    "live region added",                // EVENT_LIVE_REGION_ADDED
+    "live region removed",              // EVENT_LIVE_REGION_REMOVED
 };
 
 #endif

accessible/interfaces/nsIAccessibleEvent.idl

@@ -428,10 +428,20 @@ interface nsIAccessibleEvent : nsISupports
    */
   const unsigned long EVENT_ANNOUNCEMENT = 0x0059;
 
+  /**
+   * A live region has been introduced. Mac only.
+   */
+  const unsigned long EVENT_LIVE_REGION_ADDED = 0x005A;
+
+  /**
+   * A live region has been removed (aria-live attribute changed). Mac Only.
+   */
+  const unsigned long EVENT_LIVE_REGION_REMOVED = 0x005B;
+
   /**
    * Help make sure event map does not get out-of-line.
    */
-  const unsigned long EVENT_LAST_ENTRY = 0x005A;
+  const unsigned long EVENT_LAST_ENTRY = 0x005C;
 
   /**
    * The type of event, based on the enumerated event values

accessible/mac/AccessibleWrap.mm

@@ -5,7 +5,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "DocAccessible.h"
+#include "DocAccessibleWrap.h"
 #include "nsObjCExceptions.h"
 #include "nsCocoaUtils.h"
 
@@ -30,7 +30,36 @@ using namespace mozilla;
 using namespace mozilla::a11y;
 
 AccessibleWrap::AccessibleWrap(nsIContent* aContent, DocAccessible* aDoc)
-    : Accessible(aContent, aDoc), mNativeObject(nil), mNativeInited(false) {}
+    : Accessible(aContent, aDoc), mNativeObject(nil), mNativeInited(false) {
+  if (aContent && aContent->IsElement() && aDoc) {
+    // Check if this accessible is a live region and queue it
+    // it for dispatching an event after it has been inserted.
+    DocAccessibleWrap* doc = static_cast<DocAccessibleWrap*>(aDoc);
+    static const dom::Element::AttrValuesArray sLiveRegionValues[] = {
+        nsGkAtoms::OFF, nsGkAtoms::polite, nsGkAtoms::assertive, nullptr};
+    int32_t attrValue = aContent->AsElement()->FindAttrValueIn(
+            kNameSpaceID_None, nsGkAtoms::aria_live, sLiveRegionValues,
+            eIgnoreCase);
+    if (attrValue == 0) {
+      // aria-live is "off", do nothing.
+    } else if (attrValue > 0) {
+      // aria-live attribute is polite or assertive. It's live!
+      doc->QueueNewLiveRegion(this);
+    } else if (const nsRoleMapEntry* roleMap =
+                   aria::GetRoleMap(aContent->AsElement())) {
+      // aria role defines it as a live region. It's live!
+      if (roleMap->liveAttRule == ePoliteLiveAttr) {
+        doc->QueueNewLiveRegion(this);
+      }
+    } else if (nsStaticAtom* value = GetAccService()->MarkupAttribute(
+                   aContent, nsGkAtoms::live)) {
+      // HTML element defines it as a live region. It's live!
+      if (value == nsGkAtoms::polite || value == nsGkAtoms::assertive) {
+        doc->QueueNewLiveRegion(this);
+      }
+    }
+  }
+}
 
 AccessibleWrap::~AccessibleWrap() {}
 
@@ -120,11 +149,17 @@ nsresult AccessibleWrap::HandleAccEvent(AccEvent* aEvent) {
   nsresult rv = Accessible::HandleAccEvent(aEvent);
   NS_ENSURE_SUCCESS(rv, rv);
 
+  uint32_t eventType = aEvent->GetEventType();
+
+  if (eventType == nsIAccessibleEvent::EVENT_SHOW) {
+    DocAccessibleWrap* doc = static_cast<DocAccessibleWrap*>(Document());
+    doc->ProcessNewLiveRegions();
+  }
+
   if (IPCAccessibilityActive()) {
     return NS_OK;
   }
 
-  uint32_t eventType = aEvent->GetEventType();
   Accessible* eventTarget = nullptr;
 
   switch (eventType) {
@@ -222,6 +257,8 @@ nsresult AccessibleWrap::HandleAccEvent(AccEvent* aEvent) {
     case nsIAccessibleEvent::EVENT_SELECTION:
     case nsIAccessibleEvent::EVENT_SELECTION_ADD:
     case nsIAccessibleEvent::EVENT_SELECTION_REMOVE:
+    case nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED:
+    case nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED:
       [nativeAcc handleAccessibleEvent:eventType];
       break;
 

accessible/mac/DocAccessibleWrap.h

@@ -23,6 +23,20 @@ class DocAccessibleWrap : public DocAccessible {
   virtual void Shutdown() override;
 
   virtual ~DocAccessibleWrap();
+
+  virtual void AttributeChanged(dom::Element* aElement, int32_t aNameSpaceID,
+                                nsAtom* aAttribute, int32_t aModType,
+                                const nsAttrValue* aOldValue) override;
+
+  void QueueNewLiveRegion(Accessible* aAccessible);
+
+  void ProcessNewLiveRegions();
+
+ protected:
+  virtual void DoInitialUpdate() override;
+
+ private:
+  AccessibleHashtable mNewLiveRegions;
 };
 
 }  // namespace a11y

accessible/mac/DocAccessibleWrap.mm

@@ -23,3 +23,77 @@ void DocAccessibleWrap::Shutdown() {
 }
 
 DocAccessibleWrap::~DocAccessibleWrap() {}
+
+void DocAccessibleWrap::AttributeChanged(dom::Element* aElement,
+                                         int32_t aNameSpaceID,
+                                         nsAtom* aAttribute, int32_t aModType,
+                                         const nsAttrValue* aOldValue) {
+  DocAccessible::AttributeChanged(aElement, aNameSpaceID, aAttribute, aModType,
+                                  aOldValue);
+  if (aAttribute == nsGkAtoms::aria_live) {
+    Accessible* accessible =
+        mContent != aElement ? GetAccessible(aElement) : this;
+    if (!accessible) {
+      return;
+    }
+
+    static const dom::Element::AttrValuesArray sLiveRegionValues[] = {
+        nsGkAtoms::OFF, nsGkAtoms::polite, nsGkAtoms::assertive, nullptr};
+    int32_t attrValue =
+        aElement->FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::aria_live,
+                                  sLiveRegionValues, eIgnoreCase);
+    if (attrValue > 0) {
+      if (!aOldValue || aOldValue->IsEmptyString() ||
+          aOldValue->Equals(nsGkAtoms::OFF, eIgnoreCase)) {
+        // This element just got an active aria-live attribute value
+        FireDelayedEvent(nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED,
+                         accessible);
+      }
+    } else {
+      if (aOldValue && (aOldValue->Equals(nsGkAtoms::polite, eIgnoreCase) ||
+                        aOldValue->Equals(nsGkAtoms::assertive, eIgnoreCase))) {
+        // This element lost an active live region
+        FireDelayedEvent(nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED,
+                         accessible);
+      } else if (attrValue == 0) {
+        // aria-live="off", check if its a role-based live region that
+        // needs to be removed.
+        if (const nsRoleMapEntry* roleMap = accessible->ARIARoleMap()) {
+          // aria role defines it as a live region. It's live!
+          if (roleMap->liveAttRule == ePoliteLiveAttr) {
+            FireDelayedEvent(nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED,
+                             accessible);
+          }
+        } else if (nsStaticAtom* value = GetAccService()->MarkupAttribute(
+                       aElement, nsGkAtoms::live)) {
+          // HTML element defines it as a live region. It's live!
+          if (value == nsGkAtoms::polite || value == nsGkAtoms::assertive) {
+            FireDelayedEvent(nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED,
+                             accessible);
+          }
+        }
+      }
+    }
+  }
+}
+
+void DocAccessibleWrap::QueueNewLiveRegion(Accessible* aAccessible) {
+  if (!aAccessible) {
+    return;
+  }
+
+  mNewLiveRegions.Put(aAccessible->UniqueID(), RefPtr{aAccessible});
+}
+
+void DocAccessibleWrap::ProcessNewLiveRegions() {
+  for (auto iter = mNewLiveRegions.Iter(); !iter.Done(); iter.Next()) {
+    FireDelayedEvent(nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED, iter.Data());
+  }
+
+  mNewLiveRegions.Clear();
+}
+
+void DocAccessibleWrap::DoInitialUpdate() {
+  DocAccessible::DoInitialUpdate();
+  ProcessNewLiveRegions();
+}

accessible/mac/Platform.mm

@@ -77,14 +77,15 @@ void ProxyDestroyed(ProxyAccessible* aProxy) {
 }
 
 void ProxyEvent(ProxyAccessible* aProxy, uint32_t aEventType) {
-  // ignore everything but focus-changed, value-changed, caret,
+  // Ignore event that we don't escape below, they aren't yet supported.
-  // selection, and document load complete events for now.
   if (aEventType != nsIAccessibleEvent::EVENT_FOCUS &&
       aEventType != nsIAccessibleEvent::EVENT_VALUE_CHANGE &&
       aEventType != nsIAccessibleEvent::EVENT_TEXT_VALUE_CHANGE &&
       aEventType != nsIAccessibleEvent::EVENT_TEXT_CARET_MOVED &&
       aEventType != nsIAccessibleEvent::EVENT_DOCUMENT_LOAD_COMPLETE &&
-      aEventType != nsIAccessibleEvent::EVENT_REORDER)
+      aEventType != nsIAccessibleEvent::EVENT_REORDER &&
+      aEventType != nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED &&
+      aEventType != nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED)
     return;
 
   mozAccessible* wrapper = GetNativeFromGeckoAccessible(aProxy);

accessible/tests/browser/mac/browser.ini

@@ -38,3 +38,4 @@ skip-if = os == 'mac' && debug # Bug 1664577
 [browser_text_selection.js]
 [browser_navigate.js]
 [browser_hierarchy.js]
+[browser_live_regions.js]

accessible/tests/browser/mac/browser_live_regions.js

@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Test live region creation and removal.
+ */
+addAccessibleTask(
+  `
+  <div id="polite">Polite region</div>
+  <div id="assertive" aria-live="assertive">Assertive region</div>
+  `,
+  async (browser, accDoc) => {
+    let liveRegionAdded = waitForEvent(EVENT_LIVE_REGION_ADDED, "polite");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document
+        .getElementById("polite")
+        .setAttribute("aria-atomic", "true");
+      content.document
+        .getElementById("polite")
+        .setAttribute("aria-live", "polite");
+    });
+    await liveRegionAdded;
+
+    let liveRegionRemoved = waitForEvent(
+      EVENT_LIVE_REGION_REMOVED,
+      "assertive"
+    );
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.getElementById("assertive").removeAttribute("aria-live");
+    });
+    await liveRegionRemoved;
+
+    liveRegionAdded = waitForEvent(EVENT_LIVE_REGION_ADDED, "new-region");
+    await SpecialPowers.spawn(browser, [], () => {
+      let newRegionElm = content.document.createElement("div");
+      newRegionElm.id = "new-region";
+      newRegionElm.setAttribute("aria-live", "assertive");
+      content.document.body.appendChild(newRegionElm);
+    });
+    await liveRegionAdded;
+
+    let loadComplete = Promise.all([
+      waitForMacEvent("AXLoadComplete"),
+      waitForEvent(EVENT_LIVE_REGION_ADDED, "region-1"),
+      waitForEvent(EVENT_LIVE_REGION_ADDED, "region-2"),
+      waitForEvent(EVENT_LIVE_REGION_ADDED, "status"),
+      waitForEvent(EVENT_LIVE_REGION_ADDED, "output"),
+    ]);
+
+    await SpecialPowers.spawn(browser, [], () => {
+      content.location = `data:text/html;charset=utf-8,
+        <div id="region-1" aria-live="polite"></div>
+        <div id="region-2" aria-live="assertive"></div>
+        <div id="region-3" aria-live="off"></div>
+        <div id="status" role="status"></div>
+        <output id="output"></output>`;
+    });
+    await loadComplete;
+
+    liveRegionRemoved = waitForEvent(EVENT_LIVE_REGION_REMOVED, "status");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document
+        .getElementById("status")
+        .setAttribute("aria-live", "off");
+    });
+    await liveRegionRemoved;
+
+    liveRegionRemoved = waitForEvent(EVENT_LIVE_REGION_REMOVED, "output");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document
+        .getElementById("output")
+        .setAttribute("aria-live", "off");
+    });
+    await liveRegionRemoved;
+  }
+);

accessible/tests/mochitest/promisified-events.js

@@ -42,6 +42,8 @@ const EVENT_VIRTUALCURSOR_CHANGED =
 const EVENT_ALERT = nsIAccessibleEvent.EVENT_ALERT;
 const EVENT_TEXT_SELECTION_CHANGED =
   nsIAccessibleEvent.EVENT_TEXT_SELECTION_CHANGED;
+const EVENT_LIVE_REGION_ADDED = nsIAccessibleEvent.EVENT_LIVE_REGION_ADDED;
+const EVENT_LIVE_REGION_REMOVED = nsIAccessibleEvent.EVENT_LIVE_REGION_REMOVED;
 
 const EventsLogger = {
   enabled: false,

xpcom/ds/StaticAtoms.py

@@ -2294,6 +2294,7 @@ STATIC_ATOMS = [
     Atom("aria_rowindextext", "aria-rowindextext"),
     Atom("aria_rowspan", "aria-rowspan"),
     Atom("aria_valuetext", "aria-valuetext"),
+    Atom("assertive", "assertive"),
     Atom("auto_generated", "auto-generated"),
     Atom("banner", "banner"),
     Atom("checkable", "checkable"),