Bug 1915262 - Fire queued live region event from content in MacOS. r=morgan

Introduce a gecko live region changed event and fire it from within content.
This way it gets coalesced in the case of many insertions/deletions.

Also, rely on text insert/delete instead of reorder because there can be cases
where the text in a leaf changes as opposed to a tree mutation.
We get text insert/delete on mutations too, so that should cover it.

Differential Revision: https://phabricator.services.mozilla.com/D224388

accessible/base/nsAccessibilityService.h

@@ -522,6 +522,7 @@ static const char kEventTypeNames[][40] = {
     "live region added",         // EVENT_LIVE_REGION_ADDED
     "live region removed",       // EVENT_LIVE_REGION_REMOVED
     "inner reorder",             // EVENT_INNER_REORDER
+    "live region changed",       // EVENT_LIVE_REGION_CHANGED
 };
 
 #endif

accessible/interfaces/nsIAccessibleEvent.idl

@@ -213,10 +213,15 @@ interface nsIAccessibleEvent : nsISupports
    */
   const unsigned long EVENT_INNER_REORDER = 0x0028;
 
+  /**
+   * A live region's contents has changed. Mac Only.
+   */
+  const unsigned long EVENT_LIVE_REGION_CHANGED = 0x0029;
+
   /**
    * Help make sure event map does not get out-of-line.
    */
-  const unsigned long EVENT_LAST_ENTRY = 0x0029;
+  const unsigned long EVENT_LAST_ENTRY = 0x002a;
 
   /**
    * The type of event, based on the enumerated event values

accessible/mac/AccessibleWrap.h

@@ -54,6 +54,8 @@ class AccessibleWrap : public LocalAccessible {
 
   virtual nsresult HandleAccEvent(AccEvent* aEvent) override;
 
+  static bool IsLiveRegion(nsIContent* aContent);
+
  protected:
   friend class xpcAccessibleMacInterface;
 

accessible/mac/AccessibleWrap.mm

@@ -35,34 +35,11 @@ AccessibleWrap::AccessibleWrap(nsIContent* aContent, DocAccessible* aDoc)
     : LocalAccessible(aContent, aDoc),
       mNativeObject(nil),
       mNativeInited(false) {
-  if (aContent && aContent->IsElement() && aDoc) {
+  if (aContent && aDoc && IsLiveRegion(aContent)) {
     // 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 = nsAccUtils::FindARIAAttrValueIn(
-        aContent->AsElement(), 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 ||
-          roleMap->liveAttRule == eAssertiveLiveAttr) {
-        doc->QueueNewLiveRegion(this);
-      }
-    } else if (nsStaticAtom* value = GetAccService()->MarkupAttribute(
-                   aContent, nsGkAtoms::aria_live)) {
-      // HTML element defines it as a live region. It's live!
-      if (value == nsGkAtoms::polite || value == nsGkAtoms::assertive) {
-        doc->QueueNewLiveRegion(this);
-      }
-    }
+    doc->QueueNewLiveRegion(this);
   }
 }
 
@@ -167,11 +144,58 @@ nsresult AccessibleWrap::HandleAccEvent(AccEvent* aEvent) {
     doc->ProcessNewLiveRegions();
   }
 
+  if ((eventType == nsIAccessibleEvent::EVENT_TEXT_INSERTED ||
+       eventType == nsIAccessibleEvent::EVENT_TEXT_REMOVED ||
+       eventType == nsIAccessibleEvent::EVENT_NAME_CHANGE) &&
+      !aEvent->FromUserInput()) {
+    for (LocalAccessible* container = aEvent->GetAccessible(); container;
+         container = container->LocalParent()) {
+      if (container->HasOwnContent() && IsLiveRegion(container->GetContent())) {
+        // We rely on EventQueue::CoalesceEvents to remove duplicates
+        Document()->FireDelayedEvent(
+            nsIAccessibleEvent::EVENT_LIVE_REGION_CHANGED, container);
+      }
+    }
+  }
+
   return NS_OK;
 
   NS_OBJC_END_TRY_BLOCK_RETURN(NS_ERROR_FAILURE);
 }
 
+bool AccessibleWrap::IsLiveRegion(nsIContent* aContent) {
+  if (!aContent->IsElement()) {
+    return false;
+  }
+
+  static const dom::Element::AttrValuesArray sLiveRegionValues[] = {
+      nsGkAtoms::OFF, nsGkAtoms::polite, nsGkAtoms::assertive, nullptr};
+  int32_t attrValue = nsAccUtils::FindARIAAttrValueIn(
+      aContent->AsElement(), 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!
+    return true;
+  } else if (const nsRoleMapEntry* roleMap =
+                 aria::GetRoleMap(aContent->AsElement())) {
+    // aria role defines it as a live region. It's live!
+    if (roleMap->liveAttRule == ePoliteLiveAttr ||
+        roleMap->liveAttRule == eAssertiveLiveAttr) {
+      return true;
+    }
+  } else if (nsStaticAtom* value = GetAccService()->MarkupAttribute(
+                 aContent, nsGkAtoms::aria_live)) {
+    // HTML element defines it as a live region. It's live!
+    if (value == nsGkAtoms::polite || value == nsGkAtoms::assertive) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // AccessibleWrap protected
 

accessible/mac/Platform.mm

@@ -99,6 +99,7 @@ void PlatformEvent(Accessible* aTarget, uint32_t aEventType) {
       aEventType != nsIAccessibleEvent::EVENT_REORDER &&
       aEventType != nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED &&
       aEventType != nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED &&
+      aEventType != nsIAccessibleEvent::EVENT_LIVE_REGION_CHANGED &&
       aEventType != nsIAccessibleEvent::EVENT_NAME_CHANGE &&
       aEventType != nsIAccessibleEvent::EVENT_OBJECT_ATTRIBUTE_CHANGED) {
     return;

accessible/mac/mozAccessible.mm

@@ -43,7 +43,6 @@ using namespace mozilla::a11y;
 @interface mozAccessible ()
 - (BOOL)providesLabelNotTitle;
 
-- (void)maybePostLiveRegionChanged;
 - (void)maybePostA11yUtilNotification;
 @end
 
@@ -869,17 +868,6 @@ struct RoleDescrComparator {
   return NO;
 }
 
-- (void)maybePostLiveRegionChanged {
-  id<MOXAccessible> liveRegion =
-      [self moxFindAncestor:^BOOL(id<MOXAccessible> moxAcc, BOOL* stop) {
-        return [moxAcc moxIsLiveRegion];
-      }];
-
-  if (liveRegion) {
-    [liveRegion moxPostNotification:@"AXLiveRegionChanged"];
-  }
-}
-
 - (void)maybePostA11yUtilNotification {
   MOZ_ASSERT(mGeckoAccessible);
   // Sometimes we use a special live region to make announcements to the user.
@@ -1004,16 +992,15 @@ struct RoleDescrComparator {
     case nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED:
       mIsLiveRegion = false;
       break;
-    case nsIAccessibleEvent::EVENT_REORDER:
-      [self maybePostLiveRegionChanged];
-      break;
-    case nsIAccessibleEvent::EVENT_NAME_CHANGE: {
+    case nsIAccessibleEvent::EVENT_NAME_CHANGE:
       if (![self providesLabelNotTitle]) {
         [self moxPostNotification:NSAccessibilityTitleChangedNotification];
       }
-      [self maybePostLiveRegionChanged];
       break;
-    }
+    case nsIAccessibleEvent::EVENT_LIVE_REGION_CHANGED:
+      MOZ_ASSERT(mIsLiveRegion);
+      [self moxPostNotification:@"AXLiveRegionChanged"];
+      break;
   }
 }
 

accessible/tests/browser/mac/browser_live_regions.js

@@ -161,5 +161,19 @@ addAccessibleTask(
     });
     await liveRegionChanged;
     ok(true, "changed aria-label");
+
+    liveRegionChanged = waitForMacEvent("AXLiveRegionChanged", "live");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.getElementById("live").firstChild.data = "The hour is ";
+    });
+    await liveRegionChanged;
+    ok(true, "changed text leaf contents");
+
+    liveRegionChanged = waitForMacEvent("AXLiveRegionChanged", "live");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.getElementById("live").firstChild.data = "";
+    });
+    await liveRegionChanged;
+    ok(true, "delete text leaf contents");
   }
 );

accessible/windows/msaa/nsEventMap.h

@@ -53,5 +53,6 @@ static const uint32_t gWinEventMap[] = {
   kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_LIVE_REGION_ADDED
   kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_LIVE_REGION_REMOVED
   kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_INNER_REORDER
+  kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_LIVE_REGION_CHANGED
     // clang-format on
 };