diff --git a/accessible/generic/HyperTextAccessible.cpp b/accessible/generic/HyperTextAccessible.cpp
index c77be0cc81e1..5e8718e432bb 100644
--- a/accessible/generic/HyperTextAccessible.cpp
+++ b/accessible/generic/HyperTextAccessible.cpp
@@ -508,7 +508,7 @@ HyperTextAccessible::FindOffset(uint32_t aOffset, nsDirection aDirection,
   const bool kIsKeyboardSelect = true; // is keyboard selection
   const bool kIsVisualBidi = false; // use visual order for bidi text
   nsPeekOffsetStruct pos(aAmount, aDirection, innerContentOffset,
-                         0, kIsJumpLinesOk, kIsScrollViewAStop,
+                         nsPoint(0, 0), kIsJumpLinesOk, kIsScrollViewAStop,
                          kIsKeyboardSelect, kIsVisualBidi,
                          aWordMovementType);
   nsresult rv = frameAtOffset->PeekOffset(&pos);
diff --git a/layout/base/SelectionCarets.cpp b/layout/base/SelectionCarets.cpp
index 8e640550e220..c4a21011c6e4 100644
--- a/layout/base/SelectionCarets.cpp
+++ b/layout/base/SelectionCarets.cpp
@@ -635,7 +635,7 @@ CompareRangeWithContentOffset(nsRange* aRange,
   nsPeekOffsetStruct pos(eSelectCluster,
                          dir,
                          offset,
-                         0,
+                         nsPoint(0, 0),
                          true,
                          true,  //limit on scrolled views
                          false,
diff --git a/layout/base/nsCaret.cpp b/layout/base/nsCaret.cpp
index 5d2d30609ef0..3a596d942650 100644
--- a/layout/base/nsCaret.cpp
+++ b/layout/base/nsCaret.cpp
@@ -700,7 +700,9 @@ nsCaret::GetCaretFrameForNodeOffset(nsFrameSelection*    aFrameSelection,
                 nsBidiLevel baseLevel = NS_GET_BASE_LEVEL(frameAfter);
                 if (baseLevel != levelAfter)
                 {
-                  nsPeekOffsetStruct pos(eSelectBeginLine, eDirPrevious, 0, 0, false, true, false, true);
+                  nsPeekOffsetStruct pos(eSelectBeginLine, eDirPrevious, 0,
+                                         nsPoint(0, 0), false, true, false,
+                                         true);
                   if (NS_SUCCEEDED(frameAfter->PeekOffset(&pos))) {
                     theFrame = pos.mResultFrame;
                     theFrameOffset = pos.mContentOffset;
@@ -733,7 +735,9 @@ nsCaret::GetCaretFrameForNodeOffset(nsFrameSelection*    aFrameSelection,
                 nsBidiLevel baseLevel = NS_GET_BASE_LEVEL(frameBefore);
                 if (baseLevel != levelBefore)
                 {
-                  nsPeekOffsetStruct pos(eSelectEndLine, eDirNext, 0, 0, false, true, false, true);
+                  nsPeekOffsetStruct pos(eSelectEndLine, eDirNext, 0,
+                                         nsPoint(0, 0), false, true, false,
+                                         true);
                   if (NS_SUCCEEDED(frameBefore->PeekOffset(&pos))) {
                     theFrame = pos.mResultFrame;
                     theFrameOffset = pos.mContentOffset;
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index 7a13d7e17fa4..1434a1c257f9 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -3091,7 +3091,7 @@ nsFrame::PeekBackwardAndForward(nsSelectionAmount aAmountBack,
     nsPeekOffsetStruct pos(eSelectCharacter,
                            eDirNext,
                            aStartPos,
-                           0,
+                           nsPoint(0, 0),
                            aJumpLines,
                            true,  //limit on scrolled views
                            false,
@@ -3107,7 +3107,7 @@ nsFrame::PeekBackwardAndForward(nsSelectionAmount aAmountBack,
   nsPeekOffsetStruct startpos(aAmountBack,
                               eDirPrevious,
                               baseOffset,
-                              0,
+                              nsPoint(0, 0),
                               aJumpLines,
                               true,  //limit on scrolled views
                               false,
@@ -3119,7 +3119,7 @@ nsFrame::PeekBackwardAndForward(nsSelectionAmount aAmountBack,
   nsPeekOffsetStruct endpos(aAmountForward,
                             eDirNext,
                             aStartPos,
-                            0,
+                            nsPoint(0, 0),
                             aJumpLines,
                             true,  //limit on scrolled views
                             false,
@@ -6084,8 +6084,10 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
       nsPoint offset;
       nsView * view; //used for call of get offset from view
       aBlockFrame->GetOffsetFromView(offset,&view);
-      nscoord newDesiredX  = aPos->mDesiredX - offset.x;//get desired x into blockframe coordinates!
-      result = it->FindFrameAt(searchingLine, newDesiredX, &resultFrame, &isBeforeFirstFrame, &isAfterLastFrame);
+      nsPoint newDesiredPos =
+        aPos->mDesiredPos - offset; //get desired position into blockframe coords
+      result = it->FindFrameAt(searchingLine, newDesiredPos, &resultFrame,
+                               &isBeforeFirstFrame, &isAfterLastFrame);
       if(NS_FAILED(result))
         continue;
     }
@@ -6116,8 +6118,6 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
       nsIFrame *storeOldResultFrame = resultFrame;
       while ( !found ){
         nsPoint point;
-        point.x = aPos->mDesiredX;
-
         nsRect tempRect = resultFrame->GetRect();
         nsPoint offset;
         nsView * view; //used for call of get offset from view
@@ -6125,7 +6125,13 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
         if (!view) {
           return NS_ERROR_FAILURE;
         }
-        point.y = tempRect.height + offset.y;
+        if (resultFrame->GetWritingMode().IsVertical()) {
+          point.y = aPos->mDesiredPos.y;
+          point.x = tempRect.width + offset.x;
+        } else {
+          point.y = tempRect.height + offset.y;
+          point.x = aPos->mDesiredPos.x;
+        }
 
         //special check. if we allow non-text selection then we can allow a hit location to fall before a table.
         //otherwise there is no way to get and click signal to fall before a table (it being a line iterator itself)
@@ -6208,7 +6214,7 @@ nsFrame::GetNextPrevLineFromeBlockFrame(nsPresContext* aPresContext,
                                       );
       }
       while ( !found ){
-        nsPoint point(aPos->mDesiredX, 0);
+        nsPoint point = aPos->mDesiredPos;
         nsView* view;
         nsPoint offset;
         resultFrame->GetOffsetFromView(offset, &view);
diff --git a/layout/generic/nsFrameSelection.h b/layout/generic/nsFrameSelection.h
index 7931397f479b..c14bc603d70a 100644
--- a/layout/generic/nsFrameSelection.h
+++ b/layout/generic/nsFrameSelection.h
@@ -63,7 +63,7 @@ struct MOZ_STACK_CLASS nsPeekOffsetStruct
   nsPeekOffsetStruct(nsSelectionAmount aAmount,
                      nsDirection aDirection,
                      int32_t aStartOffset,
-                     nscoord aDesiredX,
+                     nsPoint aDesiredPos,
                      bool aJumpLines,
                      bool aScrollViewStop,
                      bool aIsKeyboardSelect,
@@ -96,9 +96,10 @@ struct MOZ_STACK_CLASS nsPeekOffsetStruct
   //               Used with: eSelectCharacter, eSelectWord
   int32_t mStartOffset;
   
-  // mDesiredX: The desired x coordinate for the caret.
-  //            Used with: eSelectLine.
-  nscoord mDesiredX;
+  // mDesiredPos: The desired inline coordinate for the caret
+  //              (one of .x or .y will be used, depending on line's writing mode)
+  //              Used with: eSelectLine.
+  nsPoint mDesiredPos;
 
   // mWordMovementType: An enum that determines whether to prefer the start or end of a word
   //                    or to use the default beahvior, which is a combination of 
@@ -645,9 +646,9 @@ private:
                          nsSelectionAmount aAmount,
                          CaretMovementStyle aMovementStyle);
 
-  nsresult     FetchDesiredX(nscoord &aDesiredX); //the x position requested by the Key Handling for up down
-  void         InvalidateDesiredX(); //do not listen to mDesiredX you must get another.
-  void         SetDesiredX(nscoord aX); //set the mDesiredX
+  nsresult     FetchDesiredPos(nsPoint &aDesiredPos); //the position requested by the Key Handling for up down
+  void         InvalidateDesiredPos(); //do not listen to mDesiredPos you must get another.
+  void         SetDesiredPos(nsPoint aPos); //set the mDesiredPos
 
   uint32_t     GetBatching() const {return mBatching; }
   bool         GetNotifyFrames() const { return mNotifyFrames; }
@@ -714,7 +715,7 @@ private:
   CaretAssociateHint mHint;   //hint to tell if the selection is at the end of this line or beginning of next
   nsBidiLevel mCaretBidiLevel;
 
-  int32_t mDesiredX;
+  nsPoint mDesiredPos;
   uint32_t mDelayedMouseEventClickCount;
   bool mDelayedMouseEventIsShift;
   bool mDelayedMouseEventValid;
@@ -724,7 +725,7 @@ private:
   bool mDragSelectingCells;
   bool mDragState;   //for drag purposes
   bool mMouseDoubleDownState; //has the doubleclick down happened
-  bool mDesiredXSet;
+  bool mDesiredPosSet;
 
   int8_t mCaretMovementStyle;
 };
diff --git a/layout/generic/nsILineIterator.h b/layout/generic/nsILineIterator.h
index 7019e71933d4..65a0243782e0 100644
--- a/layout/generic/nsILineIterator.h
+++ b/layout/generic/nsILineIterator.h
@@ -6,7 +6,7 @@
 #define nsILineIterator_h___
 
 #include "nscore.h"
-#include "nsCoord.h"
+#include "nsPoint.h"
 #include "mozilla/Attributes.h"
 
 class nsIFrame;
@@ -82,15 +82,16 @@ public:
   virtual int32_t FindLineContaining(nsIFrame* aFrame,
                                      int32_t aStartLine = 0) = 0;
 
-  // Given a line number and an X coordinate, find the frame on the
-  // line that is nearest to the X coordinate. The
-  // aXIsBeforeFirstFrame and aXIsAfterLastFrame flags are updated
+  // Given a line number and a coordinate, find the frame on the line
+  // that is nearest to aPos along the inline axis. (The block-axis coord
+  // of aPos is irrelevant.)
+  // The aPosIsBeforeFirstFrame and aPosIsAfterLastFrame flags are updated
   // appropriately.
   NS_IMETHOD FindFrameAt(int32_t aLineNumber,
-                         nscoord aX,
+                         nsPoint aPos,
                          nsIFrame** aFrameFound,
-                         bool* aXIsBeforeFirstFrame,
-                         bool* aXIsAfterLastFrame) = 0;
+                         bool* aPosIsBeforeFirstFrame,
+                         bool* aPosIsAfterLastFrame) = 0;
 
   // Give the line iterator implementor a chance todo something more complicated than
   // nsIFrame::GetNextSibling()
diff --git a/layout/generic/nsLineBox.cpp b/layout/generic/nsLineBox.cpp
index eb3e7ac803fe..85a90439aff4 100644
--- a/layout/generic/nsLineBox.cpp
+++ b/layout/generic/nsLineBox.cpp
@@ -711,14 +711,14 @@ nsLineIterator::CheckLineOrder(int32_t                  aLine,
 
 NS_IMETHODIMP
 nsLineIterator::FindFrameAt(int32_t aLineNumber,
-                            nscoord aX,
+                            nsPoint aPos,
                             nsIFrame** aFrameFound,
-                            bool* aXIsBeforeFirstFrame,
-                            bool* aXIsAfterLastFrame)
+                            bool* aPosIsBeforeFirstFrame,
+                            bool* aPosIsAfterLastFrame)
 {
-  NS_PRECONDITION(aFrameFound && aXIsBeforeFirstFrame && aXIsAfterLastFrame,
+  NS_PRECONDITION(aFrameFound && aPosIsBeforeFirstFrame && aPosIsAfterLastFrame,
                   "null OUT ptr");
-  if (!aFrameFound || !aXIsBeforeFirstFrame || !aXIsAfterLastFrame) {
+  if (!aFrameFound || !aPosIsBeforeFirstFrame || !aPosIsAfterLastFrame) {
     return NS_ERROR_NULL_POINTER;
   }
   if ((aLineNumber < 0) || (aLineNumber >= mNumLines)) {
@@ -728,8 +728,8 @@ nsLineIterator::FindFrameAt(int32_t aLineNumber,
   nsLineBox* line = mLines[aLineNumber];
   if (!line) {
     *aFrameFound = nullptr;
-    *aXIsBeforeFirstFrame = true;
-    *aXIsAfterLastFrame = false;
+    *aPosIsBeforeFirstFrame = true;
+    *aPosIsAfterLastFrame = false;
     return NS_OK;
   }
 
@@ -737,51 +737,58 @@ nsLineIterator::FindFrameAt(int32_t aLineNumber,
     return NS_ERROR_FAILURE;
 
   nsIFrame* frame = line->mFirstChild;
-  nsIFrame* closestFromLeft = nullptr;
-  nsIFrame* closestFromRight = nullptr;
+  nsIFrame* closestFromStart = nullptr;
+  nsIFrame* closestFromEnd = nullptr;
+
+  WritingMode wm = line->mWritingMode;
+  nscoord cw = line->mContainerWidth;
+
+  LogicalPoint pos(wm, aPos, cw);
+
   int32_t n = line->GetChildCount();
   while (n--) {
-    nsRect rect = frame->GetRect();
-    if (rect.width > 0) {
-      // If aX is inside this frame - this is it
-      if (rect.x <= aX && rect.XMost() > aX) {
-        closestFromLeft = closestFromRight = frame;
+    LogicalRect rect = frame->GetLogicalRect(wm, cw);
+    if (rect.ISize(wm) > 0) {
+      // If pos.I() is inside this frame - this is it
+      if (rect.IStart(wm) <= pos.I(wm) && rect.IEnd(wm) > pos.I(wm)) {
+        closestFromStart = closestFromEnd = frame;
         break;
       }
-      if (rect.x < aX) {
-        if (!closestFromLeft || 
-            rect.XMost() > closestFromLeft->GetRect().XMost())
-          closestFromLeft = frame;
+      if (rect.IStart(wm) < pos.I(wm)) {
+        if (!closestFromStart || 
+            rect.IEnd(wm) > closestFromStart->GetLogicalRect(wm, cw).IEnd(wm))
+          closestFromStart = frame;
       }
       else {
-        if (!closestFromRight ||
-            rect.x < closestFromRight->GetRect().x)
-          closestFromRight = frame;
+        if (!closestFromEnd ||
+            rect.IStart(wm) < closestFromEnd->GetLogicalRect(wm, cw).IStart(wm))
+          closestFromEnd = frame;
       }
     }
     frame = frame->GetNextSibling();
   }
-  if (!closestFromLeft && !closestFromRight) {
+  if (!closestFromStart && !closestFromEnd) {
     // All frames were zero-width. Just take the first one.
-    closestFromLeft = closestFromRight = line->mFirstChild;
+    closestFromStart = closestFromEnd = line->mFirstChild;
   }
-  *aXIsBeforeFirstFrame = mRightToLeft ? !closestFromRight : !closestFromLeft;
-  *aXIsAfterLastFrame = mRightToLeft ? !closestFromLeft : !closestFromRight;
-  if (closestFromLeft == closestFromRight) {
-    *aFrameFound = closestFromLeft;
+  *aPosIsBeforeFirstFrame = mRightToLeft ? !closestFromEnd : !closestFromStart;
+  *aPosIsAfterLastFrame = mRightToLeft ? !closestFromStart : !closestFromEnd;
+  if (closestFromStart == closestFromEnd) {
+    *aFrameFound = closestFromStart;
   }
-  else if (!closestFromLeft) {
-    *aFrameFound = closestFromRight;
+  else if (!closestFromStart) {
+    *aFrameFound = closestFromEnd;
   }
-  else if (!closestFromRight) {
-    *aFrameFound = closestFromLeft;
+  else if (!closestFromEnd) {
+    *aFrameFound = closestFromStart;
   }
   else { // we're between two frames
-    nscoord delta = closestFromRight->GetRect().x - closestFromLeft->GetRect().XMost();
-    if (aX < closestFromLeft->GetRect().XMost() + delta/2)
-      *aFrameFound = closestFromLeft;
+    nscoord delta = closestFromEnd->GetLogicalRect(wm, cw).IStart(wm) -
+                    closestFromStart->GetLogicalRect(wm, cw).IEnd(wm);
+    if (pos.I(wm) < closestFromStart->GetLogicalRect(wm, cw).IEnd(wm) + delta/2)
+      *aFrameFound = closestFromStart;
     else
-      *aFrameFound = closestFromRight;
+      *aFrameFound = closestFromEnd;
   }
   return NS_OK;
 }
diff --git a/layout/generic/nsLineBox.h b/layout/generic/nsLineBox.h
index 2f650adb8c38..f20b3a27c455 100644
--- a/layout/generic/nsLineBox.h
+++ b/layout/generic/nsLineBox.h
@@ -1705,10 +1705,10 @@ public:
                      uint32_t* aLineFlags) MOZ_OVERRIDE;
   virtual int32_t FindLineContaining(nsIFrame* aFrame, int32_t aStartLine = 0) MOZ_OVERRIDE;
   NS_IMETHOD FindFrameAt(int32_t aLineNumber,
-                         nscoord aX,
+                         nsPoint aPos,
                          nsIFrame** aFrameFound,
-                         bool* aXIsBeforeFirstFrame,
-                         bool* aXIsAfterLastFrame) MOZ_OVERRIDE;
+                         bool* aPosIsBeforeFirstFrame,
+                         bool* aPosIsAfterLastFrame) MOZ_OVERRIDE;
 
   NS_IMETHOD GetNextSiblingOnLine(nsIFrame*& aFrame, int32_t aLineNumber) MOZ_OVERRIDE;
   NS_IMETHOD CheckLineOrder(int32_t                  aLine,
diff --git a/layout/generic/nsSelection.cpp b/layout/generic/nsSelection.cpp
index ce6c09d78283..425d3a7dd224 100644
--- a/layout/generic/nsSelection.cpp
+++ b/layout/generic/nsSelection.cpp
@@ -48,7 +48,6 @@ static NS_DEFINE_CID(kFrameTraversalCID, NS_FRAMETRAVERSAL_CID);
 #include "mozilla/Preferences.h"
 #include "nsDOMClassInfoID.h"
 
-//included for desired x position;
 #include "nsPresContext.h"
 #include "nsIPresShell.h"
 #include "nsCaret.h"
@@ -108,7 +107,7 @@ static void printRange(nsRange *aDomRange);
 nsPeekOffsetStruct::nsPeekOffsetStruct(nsSelectionAmount aAmount,
                                        nsDirection aDirection,
                                        int32_t aStartOffset,
-                                       nscoord aDesiredX,
+                                       nsPoint aDesiredPos,
                                        bool aJumpLines,
                                        bool aScrollViewStop,
                                        bool aIsKeyboardSelect,
@@ -117,7 +116,7 @@ nsPeekOffsetStruct::nsPeekOffsetStruct(nsSelectionAmount aAmount,
   : mAmount(aAmount)
   , mDirection(aDirection)
   , mStartOffset(aStartOffset)
-  , mDesiredX(aDesiredX)
+  , mDesiredPos(aDesiredPos)
   , mWordMovementType(aWordMovementType)
   , mJumpLines(aJumpLines)
   , mScrollViewStop(aScrollViewStop)
@@ -436,57 +435,55 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(nsFrameSelection, AddRef)
 NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(nsFrameSelection, Release)
 
-
+// Get the x (or y, in vertical writing mode) position requested
+// by the Key Handling for line-up/down
 nsresult
-nsFrameSelection::FetchDesiredX(nscoord &aDesiredX) //the x position requested by the Key Handling for up down
+nsFrameSelection::FetchDesiredPos(nsPoint &aDesiredPos)
 {
-  if (!mShell)
-  {
-    NS_ERROR("fetch desired X failed");
+  if (!mShell) {
+    NS_ERROR("fetch desired position failed");
     return NS_ERROR_FAILURE;
   }
-  if (mDesiredXSet)
-  {
-    aDesiredX = mDesiredX;
+  if (mDesiredPosSet) {
+    aDesiredPos = mDesiredPos;
     return NS_OK;
   }
 
   nsRefPtr<nsCaret> caret = mShell->GetCaret();
-  if (!caret)
+  if (!caret) {
     return NS_ERROR_NULL_POINTER;
+  }
 
   int8_t index = GetIndexFromSelectionType(nsISelectionController::SELECTION_NORMAL);
   caret->SetSelection(mDomSelections[index]);
 
   nsRect coord;
   nsIFrame* caretFrame = caret->GetGeometry(&coord);
-  if (!caretFrame)
+  if (!caretFrame) {
     return NS_ERROR_FAILURE;
+  }
   nsPoint viewOffset(0, 0);
   nsView* view = nullptr;
   caretFrame->GetOffsetFromView(viewOffset, &view);
-  if (view)
-    coord.x += viewOffset.x;
-
-  aDesiredX = coord.x;
+  if (view) {
+    coord += viewOffset;
+  }
+  aDesiredPos = coord.TopLeft();
   return NS_OK;
 }
 
-
-
 void
-nsFrameSelection::InvalidateDesiredX() //do not listen to mDesiredX you must get another.
+nsFrameSelection::InvalidateDesiredPos() // do not listen to mDesiredPos;
+                                         // you must get another.
 {
-  mDesiredXSet = false;
+  mDesiredPosSet = false;
 }
 
-
-
 void
-nsFrameSelection::SetDesiredX(nscoord aX) //set the mDesiredX
+nsFrameSelection::SetDesiredPos(nsPoint aPos)
 {
-  mDesiredX = aX;
-  mDesiredXSet = true;
+  mDesiredPos = aPos;
+  mDesiredPosSet = true;
 }
 
 nsresult
@@ -718,7 +715,7 @@ nsFrameSelection::Init(nsIPresShell *aShell, nsIContent *aLimiter)
 {
   mShell = aShell;
   mDragState = false;
-  mDesiredXSet = false;
+  mDesiredPosSet = false;
   mLimiter = aLimiter;
   mCaretMovementStyle =
     Preferences::GetInt("bidi.edit.caret_movement_style", 2);
@@ -766,7 +763,7 @@ nsFrameSelection::MoveCaret(nsDirection       aDirection,
     return NS_ERROR_FAILURE;
 
   bool isCollapsed;
-  nscoord desiredX = 0; //we must keep this around and revalidate it when its just UP/DOWN
+  nsPoint desiredPos(0, 0); //we must keep this around and revalidate it when its just UP/DOWN
 
   int8_t index = GetIndexFromSelectionType(nsISelectionController::SELECTION_NORMAL);
   nsRefPtr<Selection> sel = mDomSelections[index];
@@ -786,13 +783,15 @@ nsFrameSelection::MoveCaret(nsDirection       aDirection,
   }
 
   nsresult result = sel->GetIsCollapsed(&isCollapsed);
-  if (NS_FAILED(result))
+  if (NS_FAILED(result)) {
     return result;
+  }
   if (aAmount == eSelectLine) {
-    result = FetchDesiredX(desiredX);
-    if (NS_FAILED(result))
+    result = FetchDesiredPos(desiredPos);
+    if (NS_FAILED(result)) {
       return result;
-    SetDesiredX(desiredX);
+    }
+    SetDesiredPos(desiredPos);
   }
 
   int32_t caretStyle = Preferences::GetInt("layout.selection.caret_style", 0);
@@ -850,7 +849,7 @@ nsFrameSelection::MoveCaret(nsDirection       aDirection,
 
   //set data using mLimiter to stop on scroll views.  If we have a limiter then we stop peeking
   //when we hit scrollable views.  If no limiter then just let it go ahead
-  nsPeekOffsetStruct pos(aAmount, eDirPrevious, offsetused, desiredX,
+  nsPeekOffsetStruct pos(aAmount, eDirPrevious, offsetused, desiredPos,
                          true, mLimiter != nullptr, true, visualMovement);
 
   nsBidiDirection paraDir = nsBidiPresUtils::ParagraphDirection(frame);
@@ -861,7 +860,7 @@ nsFrameSelection::MoveCaret(nsDirection       aDirection,
     case eSelectCluster:
     case eSelectWord:
     case eSelectWordNoSpace:
-      InvalidateDesiredX();
+      InvalidateDesiredPos();
       pos.mAmount = aAmount;
       pos.mDirection = (visualMovement && paraDir == NSBIDI_RTL)
                        ? nsDirection(1 - aDirection) : aDirection;
@@ -872,7 +871,7 @@ nsFrameSelection::MoveCaret(nsDirection       aDirection,
       break;
     case eSelectBeginLine:
     case eSelectEndLine:
-      InvalidateDesiredX();
+      InvalidateDesiredPos();
       pos.mAmount = aAmount;
       pos.mDirection = (visualMovement && paraDir == NSBIDI_RTL)
                        ? nsDirection(1 - aDirection) : aDirection;
@@ -1369,7 +1368,7 @@ nsFrameSelection::HandleClick(nsIContent*        aNewFocus,
   if (!aNewFocus)
     return NS_ERROR_INVALID_ARG;
 
-  InvalidateDesiredX();
+  InvalidateDesiredPos();
 
   if (!aContinueSelection) {
     mMaintainRange = nullptr;
@@ -1441,15 +1440,16 @@ nsFrameSelection::HandleDrag(nsIFrame *aFrame, nsPoint aPoint)
     if (frame && amount == eSelectWord && direction == eDirPrevious) {
       // To avoid selecting the previous word when at start of word,
       // first move one character forward.
-      nsPeekOffsetStruct charPos(eSelectCharacter, eDirNext, offset, 0,
-                                 false, mLimiter != nullptr, false, false);
+      nsPeekOffsetStruct charPos(eSelectCharacter, eDirNext, offset,
+                                 nsPoint(0, 0), false, mLimiter != nullptr,
+                                 false, false);
       if (NS_SUCCEEDED(frame->PeekOffset(&charPos))) {
         frame = charPos.mResultFrame;
         offset = charPos.mContentOffset;
       }
     }
 
-    nsPeekOffsetStruct pos(amount, direction, offset, 0,
+    nsPeekOffsetStruct pos(amount, direction, offset, nsPoint(0, 0),
                            false, mLimiter != nullptr, false, false);
 
     if (frame && NS_SUCCEEDED(frame->PeekOffset(&pos)) && pos.mResultContent) {
@@ -1538,17 +1538,16 @@ nsFrameSelection::TakeFocus(nsIContent*        aNewFocus,
       mDomSelections[index]->AddRange(newRange);
       mBatching = batching;
       mChangesDuringBatching = changes;
-    }
-    else
-    {
-      bool oldDesiredXSet = mDesiredXSet; //need to keep old desired X if it was set.
+    } else {
+      bool oldDesiredPosSet = mDesiredPosSet; //need to keep old desired position if it was set.
       mDomSelections[index]->Collapse(aNewFocus, aContentOffset);
-      mDesiredXSet = oldDesiredXSet; //now reset desired X back.
+      mDesiredPosSet = oldDesiredPosSet; //now reset desired pos back.
       mBatching = batching;
       mChangesDuringBatching = changes;
     }
-    if (aContentEndOffset != aContentOffset)
+    if (aContentEndOffset != aContentOffset) {
       mDomSelections[index]->Extend(aNewFocus, aContentEndOffset);
+    }
 
     //find out if we are inside a table. if so, find out which one and which cell
     //once we do that, the next time we get a takefocus, check the parent tree. 
@@ -1857,10 +1856,11 @@ nsFrameSelection::CommonPageMove(bool aForward,
     return;
 
   // find out where the caret is.
-  // we should know mDesiredX value of nsFrameSelection, but I havent seen that behavior in other windows applications yet.
+  // we should know mDesiredPos value of nsFrameSelection, but I havent seen that behavior in other windows applications yet.
   nsISelection* domSel = GetSelection(nsISelectionController::SELECTION_NORMAL);
-  if (!domSel) 
+  if (!domSel) {
     return;
+  }
 
   nsRect caretPos;
   nsIFrame* caretFrame = nsCaret::GetGeometry(domSel, &caretPos);
@@ -4592,7 +4592,7 @@ Selection::Collapse(nsINode& aParentNode, uint32_t aOffset, ErrorResult& aRv)
 
   nsCOMPtr<nsINode> kungfuDeathGrip = &aParentNode;
 
-  mFrameSelection->InvalidateDesiredX();
+  mFrameSelection->InvalidateDesiredPos();
   if (!IsValidSelectionPoint(mFrameSelection, &aParentNode)) {
     aRv.Throw(NS_ERROR_FAILURE);
     return;
@@ -5887,9 +5887,9 @@ Selection::SelectionLanguageChange(bool aLangRTL)
       mFrameSelection->SetCaretBidiLevel(levelAfter);
   }
   
-  // The caret might have moved, so invalidate the desired X position
+  // The caret might have moved, so invalidate the desired position
   // for future usages of up-arrow or down-arrow
-  mFrameSelection->InvalidateDesiredX();
+  mFrameSelection->InvalidateDesiredPos();
   
   return NS_OK;
 }
diff --git a/layout/tables/nsTableRowGroupFrame.cpp b/layout/tables/nsTableRowGroupFrame.cpp
index afc13285e6d2..33d2a60eff82 100644
--- a/layout/tables/nsTableRowGroupFrame.cpp
+++ b/layout/tables/nsTableRowGroupFrame.cpp
@@ -1732,84 +1732,89 @@ nsTableRowGroupFrame::CheckLineOrder(int32_t                  aLine,
 
 NS_IMETHODIMP
 nsTableRowGroupFrame::FindFrameAt(int32_t    aLineNumber, 
-                                  nscoord    aX, 
+                                  nsPoint    aPos, 
                                   nsIFrame** aFrameFound,
-                                  bool*    aXIsBeforeFirstFrame, 
-                                  bool*    aXIsAfterLastFrame)
+                                  bool*    aPosIsBeforeFirstFrame, 
+                                  bool*    aPosIsAfterLastFrame)
 {
-   nsTableFrame* table = nsTableFrame::GetTableFrame(this);
-   nsTableCellMap* cellMap = table->GetCellMap();
-   
-   *aFrameFound = nullptr;
-   *aXIsBeforeFirstFrame = true;
-   *aXIsAfterLastFrame = false;
+  nsTableFrame* table = nsTableFrame::GetTableFrame(this);
+  nsTableCellMap* cellMap = table->GetCellMap();
 
-   aLineNumber += GetStartRowIndex();
-   int32_t numCells = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
-   if (numCells == 0) {
-     return NS_OK;
-   }
+  WritingMode wm = table->GetWritingMode();
+  nscoord cw = table->GetRect().width;
+  LogicalPoint pos(wm, aPos, cw);
   
-   nsIFrame* frame = nullptr;
-   int32_t colCount = table->GetColCount();
-   for (int32_t i = 0; i < colCount; i++) {
-     CellData* data = cellMap->GetDataAt(aLineNumber, i);
-     if (data && data->IsOrig()) {
-       frame = (nsIFrame*)data->GetCellFrame();
-       break;
-     }
-   }
-   NS_ASSERTION(frame, "cellmap is lying");
-   bool isRTL = (NS_STYLE_DIRECTION_RTL ==
-                   table->StyleVisibility()->mDirection);
-   
-   nsIFrame* closestFromLeft = nullptr;
-   nsIFrame* closestFromRight = nullptr;
-   int32_t n = numCells;
-   nsIFrame* firstFrame = frame;
-   while (n--) {
-     nsRect rect = frame->GetRect();
-     if (rect.width > 0) {
-       // If aX is inside this frame - this is it
-       if (rect.x <= aX && rect.XMost() > aX) {
-         closestFromLeft = closestFromRight = frame;
-         break;
-       }
-       if (rect.x < aX) {
-         if (!closestFromLeft ||
-             rect.XMost() > closestFromLeft->GetRect().XMost())
-           closestFromLeft = frame;
-       }
-       else {
-         if (!closestFromRight ||
-             rect.x < closestFromRight->GetRect().x)
-           closestFromRight = frame;
-       }
-     }
-     frame = frame->GetNextSibling();
-   }
-   if (!closestFromLeft && !closestFromRight) {
-     // All frames were zero-width. Just take the first one.
-     closestFromLeft = closestFromRight = firstFrame;
-   }
-   *aXIsBeforeFirstFrame = isRTL ? !closestFromRight : !closestFromLeft;
-   *aXIsAfterLastFrame =   isRTL ? !closestFromLeft : !closestFromRight;
-   if (closestFromLeft == closestFromRight) {
-     *aFrameFound = closestFromLeft;
-   }
-   else if (!closestFromLeft) {
-     *aFrameFound = closestFromRight;
-   }
-   else if (!closestFromRight) {
-     *aFrameFound = closestFromLeft;
-   }
-   else { // we're between two frames
-     nscoord delta = closestFromRight->GetRect().x -
-                     closestFromLeft->GetRect().XMost();
-     if (aX < closestFromLeft->GetRect().XMost() + delta/2)
-       *aFrameFound = closestFromLeft;
-     else
-       *aFrameFound = closestFromRight;
+  *aFrameFound = nullptr;
+  *aPosIsBeforeFirstFrame = true;
+  *aPosIsAfterLastFrame = false;
+
+  aLineNumber += GetStartRowIndex();
+  int32_t numCells = cellMap->GetNumCellsOriginatingInRow(aLineNumber);
+  if (numCells == 0) {
+    return NS_OK;
+  }
+  
+  nsIFrame* frame = nullptr;
+  int32_t colCount = table->GetColCount();
+  for (int32_t i = 0; i < colCount; i++) {
+    CellData* data = cellMap->GetDataAt(aLineNumber, i);
+    if (data && data->IsOrig()) {
+      frame = (nsIFrame*)data->GetCellFrame();
+      break;
+    }
+  }
+  NS_ASSERTION(frame, "cellmap is lying");
+  bool isRTL = (NS_STYLE_DIRECTION_RTL ==
+                  table->StyleVisibility()->mDirection);
+  
+  nsIFrame* closestFromStart = nullptr;
+  nsIFrame* closestFromEnd = nullptr;
+  int32_t n = numCells;
+  nsIFrame* firstFrame = frame;
+  while (n--) {
+    LogicalRect rect = frame->GetLogicalRect(wm, cw);
+    if (rect.ISize(wm) > 0) {
+      // If pos.I() is inside this frame - this is it
+      if (rect.IStart(wm) <= pos.I(wm) && rect.IEnd(wm) > pos.I(wm)) {
+        closestFromStart = closestFromEnd = frame;
+        break;
+      }
+      if (rect.IStart(wm) < pos.I(wm)) {
+        if (!closestFromStart ||
+            rect.IEnd(wm) > closestFromStart->GetLogicalRect(wm, cw).IEnd(wm))
+          closestFromStart = frame;
+      }
+      else {
+        if (!closestFromEnd ||
+            rect.IStart(wm) < closestFromEnd->GetLogicalRect(wm, cw).IStart(wm))
+          closestFromEnd = frame;
+      }
+    }
+    frame = frame->GetNextSibling();
+  }
+  if (!closestFromStart && !closestFromEnd) {
+    // All frames were zero-width. Just take the first one.
+    closestFromStart = closestFromEnd = firstFrame;
+  }
+  *aPosIsBeforeFirstFrame = isRTL ? !closestFromEnd : !closestFromStart;
+  *aPosIsAfterLastFrame =   isRTL ? !closestFromStart : !closestFromEnd;
+  if (closestFromStart == closestFromEnd) {
+    *aFrameFound = closestFromStart;
+  }
+  else if (!closestFromStart) {
+    *aFrameFound = closestFromEnd;
+  }
+  else if (!closestFromEnd) {
+    *aFrameFound = closestFromStart;
+  }
+  else { // we're between two frames
+    nscoord delta = closestFromEnd->GetLogicalRect(wm, cw).IStart(wm) -
+                    closestFromStart->GetLogicalRect(wm, cw).IEnd(wm);
+    if (pos.I(wm) < closestFromStart->GetLogicalRect(wm, cw).IEnd(wm) + delta/2) {
+      *aFrameFound = closestFromStart;
+    } else {
+      *aFrameFound = closestFromEnd;
+    }
   }
   return NS_OK;
 }
diff --git a/layout/tables/nsTableRowGroupFrame.h b/layout/tables/nsTableRowGroupFrame.h
index e4864d8295cc..06345a8f7713 100644
--- a/layout/tables/nsTableRowGroupFrame.h
+++ b/layout/tables/nsTableRowGroupFrame.h
@@ -228,21 +228,21 @@ public:
   virtual int32_t FindLineContaining(nsIFrame* aFrame, int32_t aStartLine = 0) MOZ_OVERRIDE;
 
   /** Find the orginating cell frame on a row that is the nearest to the
-    * coordinate X.
+    * inline-dir coordinate of aPos.
     * @param aLineNumber          - the index of the row relative to the row group
-    * @param aX                   - X coordinate in twips relative to the
+    * @param aPos                 - coordinate in twips relative to the
     *                               origin of the row group
     * @param aFrameFound          - pointer to the cellframe
-    * @param aXIsBeforeFirstFrame - the point is before the first originating
+    * @param aPosIsBeforeFirstFrame - the point is before the first originating
     *                               cellframe
-    * @param aXIsAfterLastFrame   - the point is after the last originating
+    * @param aPosIsAfterLastFrame   - the point is after the last originating
     *                               cellframe
     */
   NS_IMETHOD FindFrameAt(int32_t aLineNumber,
-                         nscoord aX,
+                         nsPoint aPos,
                          nsIFrame** aFrameFound,
-                         bool* aXIsBeforeFirstFrame,
-                         bool* aXIsAfterLastFrame) MOZ_OVERRIDE;
+                         bool* aPosIsBeforeFirstFrame,
+                         bool* aPosIsAfterLastFrame) MOZ_OVERRIDE;
 
    /** Check whether visual and logical order of cell frames within a line are
      * identical. As the layout will reorder them this is always the case