Bug 1688972 - Make FocusedChild work across document/process boundaries. r=Jamie

Differential Revision: https://phabricator.services.mozilla.com/D103102

accessible/ipc/other/DocAccessibleChild.cpp

@@ -1524,15 +1524,30 @@ mozilla::ipc::IPCResult DocAccessibleChild::RecvTakeFocus(const uint64_t& aID) {
 }
 
 mozilla::ipc::IPCResult DocAccessibleChild::RecvFocusedChild(
-    const uint64_t& aID, uint64_t* aChild, bool* aOk) {
-  *aChild = 0;
-  *aOk = false;
+    const uint64_t& aID, PDocAccessibleChild** aResultDoc,
+    uint64_t* aResultID) {
+  *aResultDoc = nullptr;
+  *aResultID = 0;
   Accessible* acc = IdToAccessible(aID);
-  if (acc) {
-    Accessible* child = acc->FocusedChild();
-    if (child) {
-      *aChild = reinterpret_cast<uint64_t>(child->UniqueID());
-      *aOk = true;
+  if (!acc) {
+    return IPC_OK();
+  }
+
+  Accessible* result = acc->FocusedChild();
+  if (result) {
+    // Accessible::FocusedChild can return an Accessible from a descendant
+    // document.
+    DocAccessibleChild* resultDoc = result->Document()->IPCDoc();
+    // We've sent the constructor for this document to the parent process.
+    // However, because the constructor is async, the parent process might
+    // get the result of this (sync) method before it runs the constructor.
+    // If we send this document in this case, the parent process will crash.
+    // Therefore, we only do this if the parent process has explicitly told
+    // us that the document has been constructed there.
+    if (resultDoc && resultDoc->IsConstructedInParentProcess()) {
+      *aResultDoc = resultDoc;
+      *aResultID =
+          result->IsDoc() ? 0 : reinterpret_cast<uint64_t>(result->UniqueID());
     }
   }
   return IPC_OK();

accessible/ipc/other/DocAccessibleChild.h

@@ -442,9 +442,9 @@ class DocAccessibleChild : public DocAccessibleChildBase {
 
   virtual mozilla::ipc::IPCResult RecvTakeFocus(const uint64_t& aID) override;
 
-  virtual mozilla::ipc::IPCResult RecvFocusedChild(const uint64_t& aID,
-                                                   uint64_t* aChild,
-                                                   bool* aOk) override;
+  virtual mozilla::ipc::IPCResult RecvFocusedChild(
+      const uint64_t& aID, PDocAccessibleChild** aResultDoc,
+      uint64_t* aResultID) override;
 
   virtual mozilla::ipc::IPCResult RecvLanguage(const uint64_t& aID,
                                                nsString* aLocale) override;

accessible/ipc/other/PDocAccessible.ipdl

@@ -310,7 +310,7 @@ child:
 
   async TakeFocus(uint64_t aID);
   nested(inside_sync) sync FocusedChild(uint64_t aID)
-    returns(uint64_t aChild, bool aOk);
+    returns(nullable PDocAccessible aResultDoc, uint64_t aResultID);
 
   nested(inside_sync) sync Language(uint64_t aID) returns(nsString aLocale);
   nested(inside_sync) sync DocType(uint64_t aID) returns(nsString aType);

accessible/ipc/other/ProxyAccessible.cpp

@@ -762,10 +762,40 @@ double ProxyAccessible::Step() {
 void ProxyAccessible::TakeFocus() { Unused << mDoc->SendTakeFocus(mID); }
 
 ProxyAccessible* ProxyAccessible::FocusedChild() {
-  uint64_t childID = 0;
-  bool ok = false;
-  Unused << mDoc->SendFocusedChild(mID, &childID, &ok);
-  return ok ? mDoc->GetAccessible(childID) : nullptr;
+  if (mOuterDoc) {
+    // If FocusedChild was called on an outer doc, it should behave
+    // like a non-doc accessible and return its focused child, or null.
+    // If the inner doc is OOP (fission), calling FocusedChild on the outer
+    // doc would return null.
+    MOZ_ASSERT(ChildrenCount() == 1);
+    ProxyAccessible* child = FirstChild();
+    MOZ_ASSERT(child->IsDoc());
+    return (child->State() & states::FOCUSED) ? child : nullptr;
+  }
+
+  auto* doc = mDoc;
+  uint64_t id = mID;
+  if (IsDoc()) {
+    // If this is a doc we should return the focused descendant, not just the
+    // direct child. In order to do that, we need to get a doc that is in
+    // the same process as the focused accessible. So we need the focused doc.
+    if (dom::BrowserParent* browser = dom::BrowserParent::GetFocused()) {
+      if (auto* focusedDoc = browser->GetTopLevelDocAccessible()) {
+        if (!focusedDoc->IsTopLevel()) {
+          // Redirect SendFocusedChild to OOP iframe doc.
+          doc = focusedDoc;
+        }
+      }
+    }
+  }
+
+  PDocAccessibleParent* resultDoc = nullptr;
+  uint64_t resultID = 0;
+  Unused << doc->SendFocusedChild(id, &resultDoc, &resultID);
+
+  auto* useDoc = static_cast<DocAccessibleParent*>(resultDoc);
+  // If useDoc is null, this means there is no focused child.
+  return useDoc ? useDoc->GetAccessible(resultID) : nullptr;
 }
 
 ProxyAccessible* ProxyAccessible::ChildAtPoint(

accessible/tests/browser/fission/browser_take_focus.js

@@ -11,9 +11,15 @@ loadScripts(
 );
 
 addAccessibleTask(
-  `<input id="textbox" value="hello"/>`,
+  `<div role="group"><input id="textbox" value="hello"/></div>`,
   async function(browser, iframeDocAcc, contentDocAcc) {
     const textbox = findAccessibleChildByID(iframeDocAcc, "textbox");
+    const iframe = findAccessibleChildByID(contentDocAcc, "default-iframe-id");
+    const iframeDoc = findAccessibleChildByID(
+      contentDocAcc,
+      "default-iframe-body-id"
+    );
+
     testStates(textbox, STATE_FOCUSABLE, 0, STATE_FOCUSED);
 
     let onFocus = waitForEvent(EVENT_FOCUS, textbox);
@@ -21,6 +27,40 @@ addAccessibleTask(
     await onFocus;
 
     testStates(textbox, STATE_FOCUSABLE | STATE_FOCUSED, 0);
+
+    if (Services.appinfo.OS == "WINNT") {
+      // focusedChild XPCOM method not implemented in windows.
+      return;
+    }
+
+    is(
+      getAccessibleDOMNodeID(contentDocAcc.focusedChild),
+      "textbox",
+      "correct focusedChild from top doc"
+    );
+
+    is(
+      getAccessibleDOMNodeID(iframeDocAcc.focusedChild),
+      "textbox",
+      "correct focusedChild from child doc"
+    );
+
+    ok(!iframe.focusedChild, "correct focusedChild from iframe (null)");
+
+    onFocus = waitForEvent(EVENT_FOCUS, iframeDoc);
+    iframeDoc.takeFocus();
+    await onFocus;
+
+    is(
+      getAccessibleDOMNodeID(contentDocAcc.focusedChild),
+      "default-iframe-body-id",
+      "correct focusedChild of child doc from top doc"
+    );
+    is(
+      getAccessibleDOMNodeID(iframe.focusedChild),
+      "default-iframe-body-id",
+      "correct focusedChild of child doc from iframe"
+    );
   },
   { topLevel: false, iframe: true, remoteIframe: true }
 );