diff --git a/widget/windows/nsTextStore.cpp b/widget/windows/nsTextStore.cpp
index cddb12b4baf6..d3e362280bf3 100644
--- a/widget/windows/nsTextStore.cpp
+++ b/widget/windows/nsTextStore.cpp
@@ -1895,7 +1895,8 @@ nsTextStore::CurrentSelection()
 
     mSelection.SetSelection(querySelection.mReply.mOffset,
                             querySelection.mReply.mString.Length(),
-                            querySelection.mReply.mReversed);
+                            querySelection.mReply.mReversed,
+                            querySelection.GetWritingMode());
   }
 
   PR_LOG(sTextStoreLog, PR_LOG_DEBUG,
@@ -2801,6 +2802,9 @@ nsTextStore::GetRequestedAttrIndex(const TS_ATTRID& aAttrID)
   if (IsEqualGUID(aAttrID, TSATTRID_Text_VerticalWriting)) {
     return eTextVerticalWriting;
   }
+  if (IsEqualGUID(aAttrID, TSATTRID_Text_Orientation)) {
+    return eTextOrientation;
+  }
   return eNotSupported;
 }
 
@@ -2812,6 +2816,8 @@ nsTextStore::GetAttrID(int32_t aIndex)
       return GUID_PROP_INPUTSCOPE;
     case eTextVerticalWriting:
       return TSATTRID_Text_VerticalWriting;
+    case eTextOrientation:
+      return TSATTRID_Text_Orientation;
     default:
       MOZ_CRASH("Invalid index? Or not implemented yet?");
       return GUID_NULL;
@@ -2980,11 +2986,21 @@ nsTextStore::RetrieveRequestedAttrs(ULONG ulCount,
           paAttrVals[count].varValue.punkVal = inputScope.forget().take();
           break;
         }
-        case eTextVerticalWriting:
-          // Currently, we don't support vertical writing mode.
+        case eTextVerticalWriting: {
+          Selection& currentSelection = CurrentSelection();
           paAttrVals[count].varValue.vt = VT_BOOL;
-          paAttrVals[count].varValue.boolVal = VARIANT_FALSE;
+          paAttrVals[count].varValue.boolVal =
+            currentSelection.GetWritingMode().IsVertical()
+            ? VARIANT_TRUE : VARIANT_FALSE;
           break;
+        }
+        case eTextOrientation: {
+          Selection& currentSelection = CurrentSelection();
+          paAttrVals[count].varValue.vt = VT_I4;
+          paAttrVals[count].varValue.lVal =
+            currentSelection.GetWritingMode().IsVertical() ? 2700 : 0;
+          break;
+        }
         default:
           MOZ_CRASH("Invalid index? Or not implemented yet?");
           break;
@@ -4893,8 +4909,10 @@ nsTextStore::Content::StartComposition(ITfCompositionView* aCompositionView,
     GetSubstring(static_cast<uint32_t>(aCompStart.mSelectionStart),
                  static_cast<uint32_t>(aCompStart.mSelectionLength)));
   if (!aPreserveSelection) {
+    // XXX Do we need to set a new writing-mode here when setting a new
+    // selection? Currently, we just preserve the existing value.
     mSelection.SetSelection(mComposition.mStart, mComposition.mString.Length(),
-                            false);
+                            false, mSelection.GetWritingMode());
   }
 }
 
diff --git a/widget/windows/nsTextStore.h b/widget/windows/nsTextStore.h
index 8b57847a91e1..6c28f53773db 100644
--- a/widget/windows/nsTextStore.h
+++ b/widget/windows/nsTextStore.h
@@ -384,13 +384,15 @@ protected:
       mACP.style.fInterimChar = FALSE;
     }
 
-    void SetSelection(uint32_t aStart, uint32_t aLength, bool aReversed)
+    void SetSelection(uint32_t aStart, uint32_t aLength, bool aReversed,
+                      mozilla::WritingMode aWritingMode)
     {
       mDirty = false;
       mACP.acpStart = static_cast<LONG>(aStart);
       mACP.acpEnd = static_cast<LONG>(aStart + aLength);
       mACP.style.ase = aReversed ? TS_AE_START : TS_AE_END;
       mACP.style.fInterimChar = FALSE;
+      mWritingMode = aWritingMode;
     }
 
     bool IsCollapsed() const
@@ -401,6 +403,9 @@ protected:
 
     void CollapseAt(uint32_t aOffset)
     {
+      // XXX This does not update the selection's mWritingMode.
+      // If it is ever used to "collapse" to an entirely new location,
+      // we may need to fix that.
       mDirty = false;
       mACP.acpStart = mACP.acpEnd = static_cast<LONG>(aOffset);
       mACP.style.ase = TS_AE_END;
@@ -462,8 +467,15 @@ protected:
       return (mACP.style.fInterimChar != FALSE);
     }
 
+    mozilla::WritingMode GetWritingMode() const
+    {
+      MOZ_ASSERT(!mDirty);
+      return mWritingMode;
+    }
+
   private:
     TS_SELECTION_ACP mACP;
+    mozilla::WritingMode mWritingMode;
     bool mDirty;
   };
   // Don't access mSelection directly except at calling MarkDirty().
@@ -706,6 +718,7 @@ protected:
     // Supported attributes
     eInputScope = 0,
     eTextVerticalWriting,
+    eTextOrientation,
 
     // Count of the supported attributes
     NUM_OF_SUPPORTED_ATTRS