--- a/accessible/ipc/DocAccessibleChild.cpp
+++ b/accessible/ipc/DocAccessibleChild.cpp
@@ -289,23 +289,24 @@ DocAccessibleChild::RecvSelectionCount(c
   *aCount = acc ? acc->SelectionCount() : 0;
   return true;
 }
 
 bool
 DocAccessibleChild::RecvTextSubstring(const uint64_t& aID,
                                       const int32_t& aStartOffset,
                                       const int32_t& aEndOffset,
-                                      nsString* aText)
+                                      nsString* aText, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (!acc) {
     return true;
   }
 
+  *aValid = acc->IsValidRange(aStartOffset, aEndOffset);
   acc->TextSubstring(aStartOffset, aEndOffset, *aText);
   return true;
 }
 
 bool
 DocAccessibleChild::RecvGetTextAfterOffset(const uint64_t& aID,
                                            const int32_t& aOffset,
                                            const int32_t& aBoundaryType,
@@ -556,71 +557,75 @@ DocAccessibleChild::RecvReplaceText(cons
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvInsertText(const uint64_t& aID,
                                    const nsString& aText,
-                                   const int32_t& aPosition)
+                                   const int32_t& aPosition, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (acc && acc->IsTextRole()) {
+    *aValid = acc->IsValidOffset(aPosition);
     acc->InsertText(aText, aPosition);
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvCopyText(const uint64_t& aID,
                                  const int32_t& aStartPos,
-                                 const int32_t& aEndPos)
+                                 const int32_t& aEndPos, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (acc && acc->IsTextRole()) {
     acc->CopyText(aStartPos, aEndPos);
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvCutText(const uint64_t& aID,
                                 const int32_t& aStartPos,
-                                const int32_t& aEndPos)
+                                const int32_t& aEndPos, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (acc && acc->IsTextRole()) {
+    *aValid = acc->IsValidRange(aStartPos, aEndPos);
     acc->CutText(aStartPos, aEndPos);
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvDeleteText(const uint64_t& aID,
                                    const int32_t& aStartPos,
-                                   const int32_t& aEndPos)
+                                   const int32_t& aEndPos, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (acc && acc->IsTextRole()) {
+    *aValid = acc->IsValidRange(aStartPos, aEndPos);
     acc->DeleteText(aStartPos, aEndPos);
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvPasteText(const uint64_t& aID,
-                                  const int32_t& aPosition)
+                                  const int32_t& aPosition, bool* aValid)
 {
   HyperTextAccessible* acc = IdToHyperTextAccessible(aID);
   if (acc && acc->IsTextRole()) {
+    *aValid = acc->IsValidOffset(aPosition);
     acc->PasteText(aPosition);
   }
 
   return true;
 }
 
 bool
 DocAccessibleChild::RecvImagePosition(const uint64_t& aID,

--- a/accessible/ipc/DocAccessibleChild.h
+++ b/accessible/ipc/DocAccessibleChild.h
@@ -70,18 +70,18 @@ public:
 
   virtual bool RecvCharacterCount(const uint64_t& aID, int32_t* aCount)
      override;
   virtual bool RecvSelectionCount(const uint64_t& aID, int32_t* aCount)
      override;
 
   virtual bool RecvTextSubstring(const uint64_t& aID,
                                  const int32_t& aStartOffset,
-                                 const int32_t& aEndOffset, nsString* aText)
-    override;
+                                 const int32_t& aEndOffset, nsString* aText,
+                                 bool* aValid) override;
 
   virtual bool RecvGetTextAfterOffset(const uint64_t& aID,
                                       const int32_t& aOffset,
                                       const int32_t& aBoundaryType,
                                       nsString* aText, int32_t* aStartOffset,
                                       int32_t* aEndOffset) override;
   virtual bool RecvGetTextAtOffset(const uint64_t& aID,
                                    const int32_t& aOffset,
@@ -161,32 +161,32 @@ public:
                                           const int32_t& aX,
                                           const int32_t& aY) override;
 
   virtual bool RecvReplaceText(const uint64_t& aID,
                                const nsString& aText) override;
 
   virtual bool RecvInsertText(const uint64_t& aID,
                               const nsString& aText,
-                              const int32_t& aPosition) override;
+                              const int32_t& aPosition, bool* aValid) override;
 
   virtual bool RecvCopyText(const uint64_t& aID,
                             const int32_t& aStartPos,
-                            const int32_t& aEndPos) override;
+                            const int32_t& aEndPos, bool* aValid) override;
 
   virtual bool RecvCutText(const uint64_t& aID,
                            const int32_t& aStartPos,
-                           const int32_t& aEndPos) override;
+                           const int32_t& aEndPos, bool* aValid) override;
 
   virtual bool RecvDeleteText(const uint64_t& aID,
                               const int32_t& aStartPos,
-                              const int32_t& aEndPos) override;
+                              const int32_t& aEndPos, bool* aValid) override;
 
   virtual bool RecvPasteText(const uint64_t& aID,
-                             const int32_t& aPosition) override;
+                             const int32_t& aPosition, bool* aValid) override;
 
   virtual bool RecvImagePosition(const uint64_t& aID,
                                  const uint32_t& aCoordType,
                                  nsIntPoint* aRetVal) override;
 
   virtual bool RecvImageSize(const uint64_t& aID,
                              nsIntSize* aRetVal) override;
 

--- a/accessible/ipc/PDocAccessible.ipdl
+++ b/accessible/ipc/PDocAccessible.ipdl
@@ -77,17 +77,17 @@ child:
   // AccessibleText
 
   // TextSubstring is getText in IDL.
   prio(high) sync CaretOffset(uint64_t aID) returns(int32_t aOffset);
   prio(high) sync SetCaretOffset(uint64_t aID, int32_t aOffset) returns (bool aValid);
   prio(high) sync CharacterCount(uint64_t aID) returns(int32_t aCount);
   prio(high) sync SelectionCount(uint64_t aID) returns(int32_t aCount);
   prio(high) sync TextSubstring(uint64_t aID, int32_t aStartOffset, int32_t
-                                aEndOffset) returns(nsString aText);
+                                aEndOffset) returns(nsString aText, bool aValid);
   prio(high) sync GetTextAfterOffset(uint64_t aID, int32_t aOffset, int32_t aBoundaryType)
     returns(nsString aText, int32_t aStartOffset, int32_t aEndOffset);
   prio(high) sync GetTextAtOffset(uint64_t aID, int32_t aOffset, int32_t aBoundaryType)
     returns(nsString aText, int32_t aStartOffset, int32_t aEndOffset);
 
   prio(high) sync GetTextBeforeOffset(uint64_t aID, int32_t aOffset, int32_t aBoundaryType)
     returns(nsString aText, int32_t aStartOffset, int32_t aEndOffset);
   prio(high) sync CharAt(uint64_t aID, int32_t aOffset) returns(uint16_t aChar);
@@ -119,21 +119,26 @@ child:
                     uint32_t aScrollType);
   ScrollSubstringToPoint(uint64_t aID,
                          int32_t aStartOffset,
                          int32_t aEndOffset,
                          uint32_t aCoordinateType,
                          int32_t aX, int32_t aY);
 
   prio(high) sync ReplaceText(uint64_t aID, nsString aText);
-  prio(high) sync InsertText(uint64_t aID, nsString aText, int32_t aPosition);
-  prio(high) sync CopyText(uint64_t aID, int32_t aStartPos, int32_t aEndPos);
-  prio(high) sync CutText(uint64_t aID, int32_t aStartPos, int32_t aEndPos);
-  prio(high) sync DeleteText(uint64_t aID, int32_t aStartPos, int32_t aEndPos);
-  prio(high) sync PasteText(uint64_t aID, int32_t aPosition);
+  prio(high) sync InsertText(uint64_t aID, nsString aText, int32_t aPosition)
+    returns(bool aValid);
+  prio(high) sync CopyText(uint64_t aID, int32_t aStartPos, int32_t aEndPos)
+    returns(bool aValid);
+  prio(high) sync CutText(uint64_t aID, int32_t aStartPos, int32_t aEndPos)
+    returns(bool aValid);
+  prio(high) sync DeleteText(uint64_t aID, int32_t aStartPos, int32_t aEndPos)
+    returns(bool aValid);
+  prio(high) sync PasteText(uint64_t aID, int32_t aPosition)
+    returns(bool aValid);
 
   prio(high) sync ImagePosition(uint64_t aID, uint32_t aCoordType) returns(nsIntPoint aRetVal);
   prio(high) sync ImageSize(uint64_t aID) returns(IntSize aRetVal);
 
   prio(high) sync StartOffset(uint64_t aID) returns(uint32_t aRetVal, bool aOk);
   prio(high) sync EndOffset(uint64_t aID) returns(uint32_t aRetVal, bool aOk);
   prio(high) sync IsLinkValid(uint64_t aID) returns(bool aRetVal);
   prio(high) sync AnchorCount(uint64_t aID) returns(uint32_t aRetVal, bool aOk);

--- a/accessible/ipc/ProxyAccessible.cpp
+++ b/accessible/ipc/ProxyAccessible.cpp
@@ -176,21 +176,23 @@ ProxyAccessible::CharacterCount()
 int32_t
 ProxyAccessible::SelectionCount()
 {
   int32_t count = 0;
   unused << mDoc->SendSelectionCount(mID, &count);
   return count;
 }
 
-void
+bool
 ProxyAccessible::TextSubstring(int32_t aStartOffset, int32_t aEndOfset,
                                nsString& aText) const
 {
-  unused << mDoc->SendTextSubstring(mID, aStartOffset, aEndOfset, &aText);
+  bool valid;
+  unused << mDoc->SendTextSubstring(mID, aStartOffset, aEndOfset, &aText, &valid);
+  return valid;
 }
 
 void
 ProxyAccessible::GetTextAfterOffset(int32_t aOffset,
                                     AccessibleTextBoundary aBoundaryType,
                                     nsString& aText, int32_t* aStartOffset,
                                     int32_t* aEndOffset)
 {
@@ -328,44 +330,54 @@ ProxyAccessible::ScrollSubstringToPoint(
 }
 
 void
 ProxyAccessible::ReplaceText(const nsString& aText)
 {
   unused << mDoc->SendReplaceText(mID, aText);
 }
 
-void
+bool
 ProxyAccessible::InsertText(const nsString& aText, int32_t aPosition)
 {
-  unused << mDoc->SendInsertText(mID, aText, aPosition);
+  bool valid;
+  unused << mDoc->SendInsertText(mID, aText, aPosition, &valid);
+  return valid;
 }
 
-void
+bool
 ProxyAccessible::CopyText(int32_t aStartPos, int32_t aEndPos)
 {
-  unused << mDoc->SendCopyText(mID, aStartPos, aEndPos);
+  bool valid;
+  unused << mDoc->SendCopyText(mID, aStartPos, aEndPos, &valid);
+  return valid;
 }
 
-void
+bool
 ProxyAccessible::CutText(int32_t aStartPos, int32_t aEndPos)
 {
-  unused << mDoc->SendCutText(mID, aStartPos, aEndPos);
+  bool valid;
+  unused << mDoc->SendCutText(mID, aStartPos, aEndPos, &valid);
+  return valid;
 }
 
-void
+bool
 ProxyAccessible::DeleteText(int32_t aStartPos, int32_t aEndPos)
 {
-  unused << mDoc->SendDeleteText(mID, aStartPos, aEndPos);
+  bool valid;
+  unused << mDoc->SendDeleteText(mID, aStartPos, aEndPos, &valid);
+  return valid;
 }
 
-void
+bool
 ProxyAccessible::PasteText(int32_t aPosition)
 {
-  unused << mDoc->SendPasteText(mID, aPosition);
+  bool valid;
+  unused << mDoc->SendPasteText(mID, aPosition, &valid);
+  return valid;
 }
 
 nsIntPoint
 ProxyAccessible::ImagePosition(uint32_t aCoordType)
 {
   nsIntPoint retVal;
   unused << mDoc->SendImagePosition(mID, aCoordType, &retVal);
   return retVal;

--- a/accessible/ipc/ProxyAccessible.h
+++ b/accessible/ipc/ProxyAccessible.h
@@ -109,17 +109,17 @@ public:
   bool SetCaretOffset(int32_t aOffset);
 
   int32_t CharacterCount();
   int32_t SelectionCount();
 
   /**
    * Get the text between the given offsets.
    */
-  void TextSubstring(int32_t aStartOffset, int32_t aEndOfset,
+  bool TextSubstring(int32_t aStartOffset, int32_t aEndOfset,
                      nsString& aText) const;
 
   void GetTextAfterOffset(int32_t aOffset, AccessibleTextBoundary aBoundaryType,
                           nsString& aText, int32_t* aStartOffset,
                           int32_t* aEndOffset);
 
   void GetTextAtOffset(int32_t aOffset, AccessibleTextBoundary aBoundaryType,
                        nsString& aText, int32_t* aStartOffset,
@@ -164,25 +164,25 @@ public:
 
   void ScrollSubstringToPoint(int32_t aStartOffset,
                               int32_t aEndOffset,
                               uint32_t aCoordinateType,
                               int32_t aX, int32_t aY);
 
   void ReplaceText(const nsString& aText);
 
-  void InsertText(const nsString& aText, int32_t aPosition);
+  bool InsertText(const nsString& aText, int32_t aPosition);
 
-  void CopyText(int32_t aStartPos, int32_t aEndPos);
+  bool CopyText(int32_t aStartPos, int32_t aEndPos);
 
-  void CutText(int32_t aStartPos, int32_t aEndPos);
+  bool CutText(int32_t aStartPos, int32_t aEndPos);
 
-  void DeleteText(int32_t aStartPos, int32_t aEndPos);
+  bool DeleteText(int32_t aStartPos, int32_t aEndPos);
 
-  void PasteText(int32_t aPosition);
+  bool PasteText(int32_t aPosition);
 
   nsIntPoint ImagePosition(uint32_t aCoordType);
 
   nsIntSize ImageSize();
 
   uint32_t StartOffset(bool* aOk);
 
   uint32_t EndOffset(bool* aOk);

copy from accessible/windows/msaa/Platform.cpp
copy to accessible/windows/ProxyWrappers.h
--- a/accessible/windows/msaa/Platform.cpp
+++ b/accessible/windows/ProxyWrappers.h
@@ -1,44 +1,22 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=2 et sw=2 tw=80: */
 /* 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/. */
-
-#include "Platform.h"
-
-#include "AccEvent.h"
-#include "Compatibility.h"
-#include "HyperTextAccessibleWrap.h"
-#include "nsWinUtils.h"
-#include "mozilla/a11y/ProxyAccessible.h"
-
-#include "mozilla/ClearOnShutdown.h"
-
-using namespace mozilla;
-using namespace mozilla::a11y;
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. *
+ */
 
-void
-a11y::PlatformInit()
-{
-  Compatibility::Init();
+#ifndef MOZILLA_A11Y_ProxyWrappers_h
+#define MOZILLA_A11Y_ProxyWrappers_h
 
-  nsWinUtils::MaybeStartWindowEmulation();
-  ClearOnShutdown(&HyperTextAccessibleWrap::sLastTextChangeAcc);
-  ClearOnShutdown(&HyperTextAccessibleWrap::sLastTextChangeString);
-}
+#include "HyperTextAccessible.h"
 
-void
-a11y::PlatformShutdown()
-{
-  ::DestroyCaret();
-
-  nsWinUtils::ShutdownWindowEmulation();
-}
+namespace mozilla {
+namespace a11y {
 
 class ProxyAccessibleWrap : public AccessibleWrap
 {
   public:
   ProxyAccessibleWrap(ProxyAccessible* aProxy) :
     AccessibleWrap(nullptr, nullptr)
   {
     mType = eProxyType;
@@ -46,30 +24,29 @@ class ProxyAccessibleWrap : public Acces
   }
 
   virtual void Shutdown() override
   {
     mBits.proxy = nullptr;
   }
 };
 
-void
-a11y::ProxyCreated(ProxyAccessible* aProxy, uint32_t)
+class HyperTextProxyAccessibleWrap : public ProxyAccessibleWrap,
+                                     public ia2AccessibleEditableText,
+                                     public ia2AccessibleHypertext
 {
-  ProxyAccessibleWrap* wrapper = new ProxyAccessibleWrap(aProxy);
-  wrapper->AddRef();
-  aProxy->SetWrapper(reinterpret_cast<uintptr_t>(wrapper));
+  HyperTextProxyAccessibleWrap(ProxyAccessible* aProxy) :
+    ProxyAccessibleWrap(aProxy) {}
+};
+
+template<typename T>
+inline ProxyAccessible*
+HyperTextProxyFor(T* aWrapper)
+{
+  static_assert(mozilla::IsBaseOf<IUnknown, T>::value, "only IAccessible* should be passed in");
+  auto wrapper = static_cast<HyperTextProxyAccessibleWrap*>(aWrapper);
+  return wrapper->IsProxy() ? wrapper->Proxy() : nullptr;
 }
 
-void
-a11y::ProxyDestroyed(ProxyAccessible* aProxy)
-{
-  ProxyAccessibleWrap* wrapper =
-    reinterpret_cast<ProxyAccessibleWrap*>(aProxy->GetWrapper());
-  wrapper->Shutdown();
-  aProxy->SetWrapper(0);
-  wrapper->Release();
+}
 }
 
-void
-a11y::ProxyEvent(ProxyAccessible*, uint32_t)
-{
-}
+#endif

--- a/accessible/windows/ia2/ia2Accessible.cpp
+++ b/accessible/windows/ia2/ia2Accessible.cpp
@@ -614,32 +614,17 @@ ia2Accessible::get_attributes(BSTR* aAtt
   // characters ":;=,\".
   if (!acc->IsProxy()) {
     nsCOMPtr<nsIPersistentProperties> attributes = acc->Attributes();
     return ConvertToIA2Attributes(attributes, aAttributes);
   }
 
   nsTArray<Attribute> attrs;
   acc->Proxy()->Attributes(&attrs);
-  nsString attrStr;
-  size_t attrCount = attrs.Length();
-  for (size_t i = 0; i < attrCount; i++) {
-    EscapeAttributeChars(attrs[i].Name());
-    EscapeAttributeChars(attrs[i].Value());
-    AppendUTF8toUTF16(attrs[i].Name(), attrStr);
-    attrStr.Append(':');
-    attrStr.Append(attrs[i].Value());
-    attrStr.Append(';');
-  }
-
-  if (attrStr.IsEmpty())
-    return S_FALSE;
-
-  *aAttributes = ::SysAllocStringLen(attrStr.get(), attrStr.Length());
-  return *aAttributes ? S_OK : E_OUTOFMEMORY;
+  return ConvertToIA2Attributes(&attrs, aAttributes);
 
   A11Y_TRYBLOCK_END
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // IAccessible2_2
 
 STDMETHODIMP
@@ -743,16 +728,38 @@ EscapeAttributeChars(String& aStr)
   static const char kCharsToEscape[] = ":;=,\\";
   while ((offset = aStr.FindCharInSet(kCharsToEscape, offset)) != kNotFound) {
     aStr.Insert('\\', offset);
     offset += 2;
   }
 }
 
 HRESULT
+ia2Accessible::ConvertToIA2Attributes(nsTArray<Attribute>* aAttributes,
+                                      BSTR* aIA2Attributes)
+{
+  nsString attrStr;
+  size_t attrCount = aAttributes->Length();
+  for (size_t i = 0; i < attrCount; i++) {
+    EscapeAttributeChars(aAttributes->ElementAt(i).Name());
+    EscapeAttributeChars(aAttributes->ElementAt(i).Value());
+    AppendUTF8toUTF16(aAttributes->ElementAt(i).Name(), attrStr);
+    attrStr.Append(':');
+    attrStr.Append(aAttributes->ElementAt(i).Value());
+    attrStr.Append(';');
+  }
+
+  if (attrStr.IsEmpty())
+    return S_FALSE;
+
+  *aIA2Attributes = ::SysAllocStringLen(attrStr.get(), attrStr.Length());
+  return *aIA2Attributes ? S_OK : E_OUTOFMEMORY;
+}
+
+HRESULT
 ia2Accessible::ConvertToIA2Attributes(nsIPersistentProperties* aAttributes,
                                       BSTR* aIA2Attributes)
 {
   *aIA2Attributes = nullptr;
 
   // The format is name:value;name:value; with \ for escaping these
   // characters ":;=,\".
 

--- a/accessible/windows/ia2/ia2Accessible.h
+++ b/accessible/windows/ia2/ia2Accessible.h
@@ -8,16 +8,17 @@
 #define mozilla_a11y_ia2Accessible_h_
 
 #include "nsISupports.h"
 
 #include "Accessible2_2.h"
 
 namespace mozilla {
 namespace a11y {
+class Attribute;
 
 class ia2Accessible : public IAccessible2_2
 {
 public:
 
   // IUnknown
   STDMETHODIMP QueryInterface(REFIID, void**);
 
@@ -101,14 +102,16 @@ public:
     /* [in] */ long maxTargets,
     /* [out, size_is(,*nTargets)] */ IUnknown*** targets,
     /* [out, retval] */ long* nTargets
   );
 
   // Helper method
   static HRESULT ConvertToIA2Attributes(nsIPersistentProperties* aAttributes,
                                         BSTR* aIA2Attributes);
+  static HRESULT ConvertToIA2Attributes(nsTArray<Attribute>* aAttributes,
+                                        BSTR* aIA2Attributes);
 };
 
 } // namespace a11y
 } // namespace mozilla
 
 #endif

--- a/accessible/windows/ia2/ia2AccessibleEditableText.cpp
+++ b/accessible/windows/ia2/ia2AccessibleEditableText.cpp
@@ -5,29 +5,34 @@
  * 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 "ia2AccessibleEditableText.h"
 
 #include "AccessibleEditableText_i.c"
 #include "HyperTextAccessible-inl.h"
 #include "HyperTextAccessibleWrap.h"
+#include "ProxyWrappers.h"
 
 #include "nsCOMPtr.h"
 #include "nsString.h"
 
 using namespace mozilla::a11y;
 
 // IAccessibleEditableText
 
 STDMETHODIMP
 ia2AccessibleEditableText::copyText(long aStartOffset, long aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->CopyText(aStartOffset, aEndOffset) ? S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidRange(aStartOffset, aEndOffset))
     return E_INVALIDARG;
 
   textAcc->CopyText(aStartOffset, aEndOffset);
@@ -36,16 +41,20 @@ ia2AccessibleEditableText::copyText(long
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleEditableText::deleteText(long aStartOffset, long aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+    if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+      return proxy->DeleteText(aStartOffset, aEndOffset) ? S_OK : E_INVALIDARG;
+    }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidRange(aStartOffset, aEndOffset))
     return E_INVALIDARG;
 
   textAcc->DeleteText(aStartOffset, aEndOffset);
@@ -54,37 +63,44 @@ ia2AccessibleEditableText::deleteText(lo
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleEditableText::insertText(long aOffset, BSTR *aText)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  uint32_t length = ::SysStringLen(*aText);
+  nsAutoString text(*aText, length);
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->InsertText(text, aOffset) ? S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidOffset(aOffset))
     return E_INVALIDARG;
 
-  uint32_t length = ::SysStringLen(*aText);
-  nsAutoString text(*aText, length);
-
   textAcc->InsertText(text, aOffset);
   return S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleEditableText::cutText(long aStartOffset, long aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->CutText(aStartOffset, aEndOffset) ? S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidRange(aStartOffset, aEndOffset))
     return E_INVALIDARG;
 
   textAcc->CutText(aStartOffset, aEndOffset);
@@ -93,16 +109,20 @@ ia2AccessibleEditableText::cutText(long 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleEditableText::pasteText(long aOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->PasteText(aOffset) ? S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidOffset(aOffset))
     return E_INVALIDARG;
 
   textAcc->PasteText(aOffset);

--- a/accessible/windows/ia2/ia2AccessibleText.cpp
+++ b/accessible/windows/ia2/ia2AccessibleText.cpp
@@ -7,26 +7,32 @@
 
 #include "ia2AccessibleText.h"
 
 #include "Accessible2.h"
 #include "AccessibleText_i.c"
 
 #include "HyperTextAccessibleWrap.h"
 #include "HyperTextAccessible-inl.h"
+#include "ProxyWrappers.h"
 
 using namespace mozilla::a11y;
 
 // IAccessibleText
 
 STDMETHODIMP
 ia2AccessibleText::addSelection(long aStartOffset, long aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->AddToSelection(aStartOffset, aEndOffset) ?
+      S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   return textAcc->AddToSelection(aStartOffset, aEndOffset) ?
     S_OK : E_INVALIDARG;
 
   A11Y_TRYBLOCK_END
@@ -40,26 +46,33 @@ ia2AccessibleText::get_attributes(long a
 
   if (!aStartOffset || !aEndOffset || !aTextAttributes)
     return E_INVALIDARG;
 
   *aStartOffset = 0;
   *aEndOffset = 0;
   *aTextAttributes = nullptr;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
+  int32_t startOffset = 0, endOffset = 0;
+  HRESULT hr;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    nsAutoTArray<Attribute, 10> attrs;
+    proxy->TextAttributes(true, aOffset, &attrs, &startOffset, &endOffset);
+    hr = AccessibleWrap::ConvertToIA2Attributes(&attrs, aTextAttributes);
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  int32_t startOffset = 0, endOffset = 0;
-  nsCOMPtr<nsIPersistentProperties> attributes =
-    textAcc->TextAttributes(true, aOffset, &startOffset, &endOffset);
+    nsCOMPtr<nsIPersistentProperties> attributes =
+      textAcc->TextAttributes(true, aOffset, &startOffset, &endOffset);
 
-  HRESULT hr = AccessibleWrap::ConvertToIA2Attributes(attributes,
-                                                      aTextAttributes);
+    hr = AccessibleWrap::ConvertToIA2Attributes(attributes, aTextAttributes);
+  }
+
   if (FAILED(hr))
     return hr;
 
   *aStartOffset = startOffset;
   *aEndOffset = endOffset;
 
   return S_OK;
 
@@ -71,21 +84,26 @@ ia2AccessibleText::get_caretOffset(long 
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aOffset)
     return E_INVALIDARG;
 
   *aOffset = -1;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    *aOffset = proxy->CaretOffset();
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  *aOffset = textAcc->CaretOffset();
+    *aOffset = textAcc->CaretOffset();
+  }
+
   return *aOffset != -1 ? S_OK : S_FALSE;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::get_characterExtents(long aOffset,
                                         enum IA2CoordinateType aCoordType,
@@ -93,25 +111,29 @@ ia2AccessibleText::get_characterExtents(
                                         long* aWidth, long* aHeight)
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aX || !aY || !aWidth || !aHeight)
     return E_INVALIDARG;
   *aX = *aY = *aWidth = *aHeight = 0;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
-
   uint32_t geckoCoordType = (aCoordType == IA2_COORDTYPE_SCREEN_RELATIVE) ?
     nsIAccessibleCoordinateType::COORDTYPE_SCREEN_RELATIVE :
     nsIAccessibleCoordinateType::COORDTYPE_PARENT_RELATIVE;
+  nsIntRect rect;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    rect = proxy->CharBounds(aOffset, geckoCoordType);
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  nsIntRect rect = textAcc->CharBounds(aOffset, geckoCoordType);
+    rect = textAcc->CharBounds(aOffset, geckoCoordType);
+  }
 
   *aX = rect.x;
   *aY = rect.y;
   *aWidth = rect.width;
   *aHeight = rect.height;
   return S_OK;
 
   A11Y_TRYBLOCK_END
@@ -121,68 +143,85 @@ STDMETHODIMP
 ia2AccessibleText::get_nSelections(long* aNSelections)
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aNSelections)
     return E_INVALIDARG;
   *aNSelections = 0;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    *aNSelections = proxy->SelectionCount();
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  *aNSelections = textAcc->SelectionCount();
+    *aNSelections = textAcc->SelectionCount();
+  }
+
   return S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::get_offsetAtPoint(long aX, long aY,
                                      enum IA2CoordinateType aCoordType,
                                      long* aOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aOffset)
     return E_INVALIDARG;
   *aOffset = 0;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
-
   uint32_t geckoCoordType = (aCoordType == IA2_COORDTYPE_SCREEN_RELATIVE) ?
     nsIAccessibleCoordinateType::COORDTYPE_SCREEN_RELATIVE :
     nsIAccessibleCoordinateType::COORDTYPE_PARENT_RELATIVE;
 
-  *aOffset = textAcc->OffsetAtPoint(aX, aY, geckoCoordType);
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    *aOffset = proxy->OffsetAtPoint(aX, aY, geckoCoordType);
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
+
+    *aOffset = textAcc->OffsetAtPoint(aX, aY, geckoCoordType);
+  }
+
   return *aOffset == -1 ? S_FALSE : S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::get_selection(long aSelectionIndex, long* aStartOffset,
                                  long* aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aStartOffset || !aEndOffset)
     return E_INVALIDARG;
   *aStartOffset = *aEndOffset = 0;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
+  int32_t startOffset = 0, endOffset = 0;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    nsString unused;
+    if (!proxy->SelectionBoundsAt(aSelectionIndex, unused, &startOffset,
+                                  &endOffset))
+      return E_INVALIDARG;
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  int32_t startOffset = 0, endOffset = 0;
-  if (!textAcc->SelectionBoundsAt(aSelectionIndex, &startOffset, &endOffset))
-    return E_INVALIDARG;
+    if (!textAcc->SelectionBoundsAt(aSelectionIndex, &startOffset, &endOffset))
+      return E_INVALIDARG;
+  }
 
   *aStartOffset = startOffset;
   *aEndOffset = endOffset;
   return S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
@@ -191,25 +230,32 @@ ia2AccessibleText::get_text(long aStartO
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aText)
     return E_INVALIDARG;
 
   *aText = nullptr;
 
-  HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
-  if (textAcc->IsDefunct())
-    return CO_E_OBJNOTCONNECTED;
+  nsAutoString text;
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    if (!proxy->TextSubstring(aStartOffset, aEndOffset, text)) {
+      return E_INVALIDARG;
+    }
+  } else {
+    HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
+    if (textAcc->IsDefunct())
+      return CO_E_OBJNOTCONNECTED;
 
-  if (!textAcc->IsValidRange(aStartOffset, aEndOffset))
-    return E_INVALIDARG;
+    if (!textAcc->IsValidRange(aStartOffset, aEndOffset))
+      return E_INVALIDARG;
 
-  nsAutoString text;
-  textAcc->TextSubstring(aStartOffset, aEndOffset, text);
+    textAcc->TextSubstring(aStartOffset, aEndOffset, text);
+  }
+
   if (text.IsEmpty())
     return S_FALSE;
 
   *aText = ::SysAllocStringLen(text.get(), text.Length());
   return *aText ? S_OK : E_OUTOFMEMORY;
 
   A11Y_TRYBLOCK_END
 }
@@ -356,31 +402,39 @@ ia2AccessibleText::get_textAtOffset(long
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::removeSelection(long aSelectionIndex)
 {
   A11Y_TRYBLOCK_BEGIN
 
+    if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+      return proxy->RemoveFromSelection(aSelectionIndex) ? S_OK : E_INVALIDARG;
+    }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   return textAcc->RemoveFromSelection(aSelectionIndex) ?
     S_OK : E_INVALIDARG;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::setCaretOffset(long aOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+    if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+      return proxy->SetCaretOffset(aOffset) ? S_OK : E_INVALIDARG;
+    }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidOffset(aOffset))
     return E_INVALIDARG;
 
   textAcc->SetCaretOffset(aOffset);
@@ -390,16 +444,21 @@ ia2AccessibleText::setCaretOffset(long a
 }
 
 STDMETHODIMP
 ia2AccessibleText::setSelection(long aSelectionIndex, long aStartOffset,
                                 long aEndOffset)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    return proxy->SetSelectionBoundsAt(aSelectionIndex, aStartOffset,
+                                       aEndOffset) ? S_OK : E_INVALIDARG;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   return textAcc->SetSelectionBoundsAt(aSelectionIndex, aStartOffset, aEndOffset) ?
     S_OK : E_INVALIDARG;
 
   A11Y_TRYBLOCK_END
@@ -409,32 +468,42 @@ STDMETHODIMP
 ia2AccessibleText::get_nCharacters(long* aNCharacters)
 {
   A11Y_TRYBLOCK_BEGIN
 
   if (!aNCharacters)
     return E_INVALIDARG;
   *aNCharacters = 0;
 
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    *aNCharacters = proxy->CharacterCount();
+    return S_OK;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   *aNCharacters  = textAcc->CharacterCount();
   return S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP
 ia2AccessibleText::scrollSubstringTo(long aStartIndex, long aEndIndex,
                                      enum IA2ScrollType aScrollType)
 {
   A11Y_TRYBLOCK_BEGIN
 
+    if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+      proxy->ScrollSubstringTo(aStartIndex, aEndIndex, aScrollType);
+      return S_OK;
+    }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidRange(aStartIndex, aEndIndex))
     return E_INVALIDARG;
 
   textAcc->ScrollSubstringTo(aStartIndex, aEndIndex, aScrollType);
@@ -445,27 +514,33 @@ ia2AccessibleText::scrollSubstringTo(lon
 
 STDMETHODIMP
 ia2AccessibleText::scrollSubstringToPoint(long aStartIndex, long aEndIndex,
                                           enum IA2CoordinateType aCoordType,
                                           long aX, long aY)
 {
   A11Y_TRYBLOCK_BEGIN
 
+  uint32_t geckoCoordType = (aCoordType == IA2_COORDTYPE_SCREEN_RELATIVE) ?
+    nsIAccessibleCoordinateType::COORDTYPE_SCREEN_RELATIVE :
+    nsIAccessibleCoordinateType::COORDTYPE_PARENT_RELATIVE;
+
+  if (ProxyAccessible* proxy = HyperTextProxyFor(this)) {
+    proxy->ScrollSubstringToPoint(aStartIndex, aEndIndex, geckoCoordType, aX,
+                                  aY);
+    return S_OK;
+  }
+
   HyperTextAccessible* textAcc = static_cast<HyperTextAccessibleWrap*>(this);
   if (textAcc->IsDefunct())
     return CO_E_OBJNOTCONNECTED;
 
   if (!textAcc->IsValidRange(aStartIndex, aEndIndex))
     return E_INVALIDARG;
 
-  uint32_t geckoCoordType = (aCoordType == IA2_COORDTYPE_SCREEN_RELATIVE) ?
-    nsIAccessibleCoordinateType::COORDTYPE_SCREEN_RELATIVE :
-    nsIAccessibleCoordinateType::COORDTYPE_PARENT_RELATIVE;
-
   textAcc->ScrollSubstringToPoint(aStartIndex, aEndIndex,
                                   geckoCoordType, aX, aY);
   return S_OK;
 
   A11Y_TRYBLOCK_END
 }
 
 STDMETHODIMP

--- a/accessible/windows/ia2/moz.build
+++ b/accessible/windows/ia2/moz.build
@@ -34,16 +34,17 @@ SOURCES += [
     'ia2AccessibleTable.cpp',
     'ia2AccessibleTableCell.cpp',
 ]
 
 LOCAL_INCLUDES += [
     '/accessible/base',
     '/accessible/generic',
     '/accessible/html',
+    '/accessible/windows',
     '/accessible/windows/msaa',
     '/accessible/xpcom',
     '/accessible/xul',
 ]
 
 FINAL_LIBRARY = 'xul'
 
 # The midl generated code include Windows headers which defines min and max

--- a/accessible/windows/msaa/Platform.cpp
+++ b/accessible/windows/msaa/Platform.cpp
@@ -6,16 +6,17 @@
 
 #include "Platform.h"
 
 #include "AccEvent.h"
 #include "Compatibility.h"
 #include "HyperTextAccessibleWrap.h"
 #include "nsWinUtils.h"
 #include "mozilla/a11y/ProxyAccessible.h"
+#include "ProxyWrappers.h"
 
 #include "mozilla/ClearOnShutdown.h"
 
 using namespace mozilla;
 using namespace mozilla::a11y;
 
 void
 a11y::PlatformInit()
@@ -30,32 +31,16 @@ a11y::PlatformInit()
 void
 a11y::PlatformShutdown()
 {
   ::DestroyCaret();
 
   nsWinUtils::ShutdownWindowEmulation();
 }
 
-class ProxyAccessibleWrap : public AccessibleWrap
-{
-  public:
-  ProxyAccessibleWrap(ProxyAccessible* aProxy) :
-    AccessibleWrap(nullptr, nullptr)
-  {
-    mType = eProxyType;
-    mBits.proxy = aProxy;
-  }
-
-  virtual void Shutdown() override
-  {
-    mBits.proxy = nullptr;
-  }
-};
-
 void
 a11y::ProxyCreated(ProxyAccessible* aProxy, uint32_t)
 {
   ProxyAccessibleWrap* wrapper = new ProxyAccessibleWrap(aProxy);
   wrapper->AddRef();
   aProxy->SetWrapper(reinterpret_cast<uintptr_t>(wrapper));
 }
 

--- a/accessible/windows/msaa/moz.build
+++ b/accessible/windows/msaa/moz.build
@@ -43,16 +43,17 @@ if CONFIG['MOZ_XUL']:
         'XULMenuAccessibleWrap.cpp',
         'XULTreeGridAccessibleWrap.cpp',
     ]
 
 LOCAL_INCLUDES += [
     '/accessible/base',
     '/accessible/generic',
     '/accessible/html',
+    '/accessible/windows',
     '/accessible/windows/ia2',
     '/accessible/windows/sdn',
     '/accessible/windows/uia',
     '/accessible/xpcom',
     '/accessible/xul',
     '/dom/base',
 ]