Bug 1611428: Add accessibilityLabel function to support aria-label on MacOS. r=eeejay,Jamie

Differential Revision: https://phabricator.services.mozilla.com/D62470

--HG--
extra : moz-landing-system : lando

accessible/ipc/ProxyAccessibleShared.h

@@ -24,8 +24,9 @@ uint64_t NativeState() const;
 
 /*
  * Set aName to the name of the proxied accessible.
+ * Return the ENameValueFlag passed from Accessible::Name
  */
-void Name(nsString& aName) const;
+uint32_t Name(nsString& aName) const;
 
 /*
  * Set aValue to the value of the proxied accessible.

accessible/ipc/other/DocAccessibleChild.cpp

@@ -102,11 +102,12 @@ mozilla::ipc::IPCResult DocAccessibleChild::RecvNativeState(const uint64_t& aID,
 }
 
 mozilla::ipc::IPCResult DocAccessibleChild::RecvName(const uint64_t& aID,
-                                                     nsString* aName) {
+                                                     nsString* aName,
+                                                     uint32_t* aFlag) {
   Accessible* acc = IdToAccessible(aID);
   if (!acc) return IPC_OK();
 
-  acc->Name(*aName);
+  *aFlag = acc->Name(*aName);
   return IPC_OK();
 }
 

accessible/ipc/other/DocAccessibleChild.h

@@ -55,8 +55,8 @@ class DocAccessibleChild : public DocAccessibleChildBase {
   /*
    * Get the name for the accessible with given id.
    */
-  virtual mozilla::ipc::IPCResult RecvName(const uint64_t& aID,
-                                           nsString* aName) override;
+  virtual mozilla::ipc::IPCResult RecvName(const uint64_t& aID, nsString* aName,
+                                           uint32_t* aFlag) override;
 
   virtual mozilla::ipc::IPCResult RecvValue(const uint64_t& aID,
                                             nsString* aValue) override;

accessible/ipc/other/PDocAccessible.ipdl

@@ -126,7 +126,7 @@ child:
   // Accessible
   nested(inside_sync) sync State(uint64_t aID) returns(uint64_t states);
   nested(inside_sync) sync NativeState(uint64_t aID) returns(uint64_t states);
-  nested(inside_sync) sync Name(uint64_t aID) returns(nsString name);
+  nested(inside_sync) sync Name(uint64_t aID) returns(nsString name, uint32_t flag);
   nested(inside_sync) sync Value(uint64_t aID) returns(nsString value);
   nested(inside_sync) sync Help(uint64_t aID) returns(nsString help);
   nested(inside_sync) sync Description(uint64_t aID) returns(nsString desc);

accessible/ipc/other/ProxyAccessible.cpp

@@ -30,8 +30,10 @@ uint64_t ProxyAccessible::NativeState() const {
   return state;
 }
 
-void ProxyAccessible::Name(nsString& aName) const {
-  Unused << mDoc->SendName(mID, &aName);
+uint32_t ProxyAccessible::Name(nsString& aName) const {
+  uint32_t flag;
+  Unused << mDoc->SendName(mID, &aName, &flag);
+  return flag;
 }
 
 void ProxyAccessible::Value(nsString& aValue) const {

accessible/ipc/win/ProxyAccessible.cpp

@@ -118,20 +118,26 @@ static ProxyAccessible* GetProxyFor(DocAccessibleParent* aDoc,
   return aDoc->GetAccessible(id);
 }
 
-void ProxyAccessible::Name(nsString& aName) const {
+uint32_t ProxyAccessible::Name(nsString& aName) const {
+  /* The return values here exist only to match behvaiour required
+   * by the header declaration of this function. On Mac, we'd like
+   * to return the associated ENameValueFlag, but we don't have
+   * access to that here, so we return a dummy eNameOK value instead.
+   */
   aName.Truncate();
   RefPtr<IAccessible> acc;
   if (!GetCOMInterface((void**)getter_AddRefs(acc))) {
-    return;
+    return eNameOK;
   }
 
   BSTR result;
   HRESULT hr = acc->get_accName(kChildIdSelf, &result);
   _bstr_t resultWrap(result, false);
   if (FAILED(hr)) {
-    return;
+    return eNameOK;
   }
   aName = (wchar_t*)resultWrap;
+  return eNameOK;
 }
 
 void ProxyAccessible::Value(nsString& aValue) const {

accessible/mac/mozAccessible.mm

@@ -274,14 +274,25 @@ static inline NSMutableArray* ConvertToNSArray(nsTArray<ProxyAccessible*>& aArra
   if ([attribute isEqualToString:NSAccessibilityTopLevelUIElementAttribute]) return [self window];
   if ([attribute isEqualToString:NSAccessibilityTitleAttribute]) return [self title];
   if ([attribute isEqualToString:NSAccessibilityTitleUIElementAttribute]) {
+    /* If our accessible is labelled by more than one item, its label
+     * should be set by accessibilityLabel instead of here, so we return nil.
+     */
     if (accWrap) {
       Relation rel = accWrap->RelationByType(RelationType::LABELLED_BY);
       Accessible* tempAcc = rel.Next();
-      return tempAcc ? GetNativeFromGeckoAccessible(tempAcc) : nil;
+      if (tempAcc && !rel.Next()) {
+        return GetNativeFromGeckoAccessible(tempAcc);
+      } else {
+        return nil;
+      }
     }
     nsTArray<ProxyAccessible*> rel = proxy->RelationByType(RelationType::LABELLED_BY);
     ProxyAccessible* tempProxy = rel.SafeElementAt(0);
-    return tempProxy ? GetNativeFromProxy(tempProxy) : nil;
+    if (tempProxy && rel.Length() <= 1) {
+      return GetNativeFromProxy(tempProxy);
+    } else {
+      return nil;
+    }
   }
   if ([attribute isEqualToString:NSAccessibilityHelpAttribute]) return [self help];
   if ([attribute isEqualToString:NSAccessibilityOrientationAttribute]) return [self orientation];
@@ -474,6 +485,43 @@ static inline NSMutableArray* ConvertToNSArray(nsTArray<ProxyAccessible*>& aArra
   return NSAccessibilityActionDescription(action);
 }
 
+- (NSString*)accessibilityLabel {
+  AccessibleWrap* accWrap = [self getGeckoAccessible];
+  ProxyAccessible* proxy = [self getProxyAccessible];
+  if (!accWrap && !proxy) {
+    return nil;
+  }
+
+  /* If our accessible is labelled by exactly one item, or if its
+   * name is obtained from a subtree, we should let
+   * NSAccessibilityTitleUIElementAttribute determine its label. */
+  if (accWrap) {
+    nsAutoString name;
+    ENameValueFlag flag = accWrap->Name(name);
+    if (flag == eNameFromSubtree) {
+      return nil;
+    }
+
+    Relation rel = accWrap->RelationByType(RelationType::LABELLED_BY);
+    if (rel.Next() && !rel.Next()) {
+      return nil;
+    }
+  } else if (proxy) {
+    nsAutoString name;
+    uint32_t flag = proxy->Name(name);
+    if (flag == eNameFromSubtree) {
+      return nil;
+    }
+
+    nsTArray<ProxyAccessible*> rels = proxy->RelationByType(RelationType::LABELLED_BY);
+    if (rels.Length() == 1) {
+      return nil;
+    }
+  }
+
+  return [self title];
+}
+
 - (void)accessibilityPerformAction:(NSString*)action {
 }