Bug 1297549: Part 2 - Propagate changes in tab native window down to content for a11y; r=jimm

MozReview-Commit-ID: 4akhzCtYciq

dom/ipc/PBrowser.ipdl

@@ -837,6 +837,14 @@ child:
      */
     async Print(uint64_t aOuterWindowID, PrintData aPrintData);
 
+    /**
+     * Update the child with the tab's current top-level native window handle.
+     * This is used by a11y objects who must expose their native window.
+     *
+     * @param aNewHandle The native window handle of the tab's top-level window.
+     */
+    async UpdateNativeWindowHandle(uintptr_t aNewHandle);
+
 /*
  * FIXME: write protocol!
 

dom/ipc/TabChild.cpp

@@ -549,6 +549,9 @@ TabChild::TabChild(nsIContentChild* aManager,
   , mDidLoadURLInit(false)
   , mAPZChild(nullptr)
   , mLayerObserverEpoch(0)
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  , mNativeWindowHandle(0)
+#endif
 {
   // In the general case having the TabParent tell us if APZ is enabled or not
   // doesn't really work because the TabParent itself may not have a reference
@@ -2534,6 +2537,17 @@ TabChild::RecvPrint(const uint64_t& aOuterWindowID, const PrintData& aPrintData)
   return true;
 }
 
+bool
+TabChild::RecvUpdateNativeWindowHandle(const uintptr_t& aNewHandle)
+{
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  mNativeWindowHandle = aNewHandle;
+  return true;
+#else
+  return false;
+#endif
+}
+
 bool
 TabChild::RecvDestroy()
 {

dom/ipc/TabChild.h

@@ -590,6 +590,8 @@ public:
   virtual bool RecvPrint(const uint64_t& aOuterWindowID,
                          const PrintData& aPrintData) override;
 
+  virtual bool RecvUpdateNativeWindowHandle(const uintptr_t& aNewHandle) override;
+
   /**
    * Native widget remoting protocol for use with windowed plugins with e10s.
    */
@@ -651,6 +653,10 @@ public:
   // Request that the docshell be marked as active.
   void ForcePaint(uint64_t aLayerObserverEpoch);
 
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  uintptr_t GetNativeWindowHandle() const { return mNativeWindowHandle; }
+#endif
+
 protected:
   virtual ~TabChild();
 
@@ -789,6 +795,11 @@ private:
   // The most recently seen layer observer epoch in RecvSetDocShellIsActive.
   uint64_t mLayerObserverEpoch;
 
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  // The handle associated with the native window that contains this tab
+  uintptr_t mNativeWindowHandle;
+#endif // defined(XP_WIN)
+
   DISALLOW_EVIL_CONSTRUCTORS(TabChild);
 };
 

dom/ipc/TabParent.cpp

@@ -400,6 +400,17 @@ TabParent::SetOwnerElement(Element* aElement)
     Unused << SendSetUseGlobalHistory(useGlobalHistory);
   }
 
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  if (!mIsDestroyed) {
+    uintptr_t newWindowHandle = 0;
+    if (nsCOMPtr<nsIWidget> widget = GetWidget()) {
+      newWindowHandle =
+        reinterpret_cast<uintptr_t>(widget->GetNativeData(NS_NATIVE_WINDOW));
+    }
+    Unused << SendUpdateNativeWindowHandle(newWindowHandle);
+  }
+#endif
+
   AddWindowListeners();
   TryCacheDPIAndScale();
 }