collapsing borders now do rounding of odd-thickness borders correctly

at the pixel level.  The odd pixel is always given to the right and bottom
cell borders whenever possible, and to the top and left table border otherwise.

layout/html/table/src/nsTableCellFrame.cpp

@@ -82,7 +82,9 @@ void nsTableCellFrame::InitCellFrame(PRInt32 aColIndex)
   }
 }
 
-void nsTableCellFrame::SetBorderEdgeLength(PRUint8 aSide, PRInt32 aIndex, nscoord aLength)
+void nsTableCellFrame::SetBorderEdgeLength(PRUint8 aSide, 
+                                           PRInt32 aIndex, 
+                                           nscoord aLength)
 {
   if ((NS_SIDE_LEFT==aSide) || (NS_SIDE_RIGHT==aSide))
   {
@@ -177,7 +179,8 @@ nsTableCellFrame::GetSkipSides() const
 void nsTableCellFrame::SetBorderEdge(PRUint8       aSide, 
                                      PRInt32       aRowIndex, 
                                      PRInt32       aColIndex, 
-                                     nsBorderEdge *aBorder)
+                                     nsBorderEdge *aBorder,
+                                     nscoord       aOddAmountToAdd)
 {
   nsBorderEdge *border = nsnull;
   switch (aSide)
@@ -216,6 +219,7 @@ void nsTableCellFrame::SetBorderEdge(PRUint8       aSide,
   }
   if (nsnull!=border) {
     *border=*aBorder;
+    border->mWidth += aOddAmountToAdd;
   }
   else {
     NS_ASSERTION(PR_FALSE, "bad border edge state");

layout/html/table/src/nsTableCellFrame.h

@@ -44,7 +44,8 @@ public:
   void SetBorderEdge(PRUint8 aSide, 
                      PRInt32 aRowIndex, 
                      PRInt32 aColIndex, 
-                     nsBorderEdge *border);
+                     nsBorderEdge *border,
+                     nscoord aOddAmountToAdd);
 
   void SetBorderEdgeLength(PRUint8 aSide, 
                            PRInt32 aIndex, 

layout/html/table/src/nsTableFrame.cpp

@@ -1196,7 +1196,8 @@ void nsTableFrame::SetBorderEdgeLength(PRUint8 aSide, PRInt32 aIndex, nscoord aL
   // the object on the right/bottom gets the extra portion
 
 /* compute the horizontal collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-void nsTableFrame::ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex,
+void nsTableFrame::ComputeHorizontalCollapsingBorders(nsIPresContext& aPresContext,
+                                                      PRInt32 aStartRowIndex,
                                                       PRInt32 aEndRowIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
@@ -1216,15 +1217,16 @@ void nsTableFrame::ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex,
     {
       if (0==rowIndex)
       { // table is top neighbor
-        ComputeTopBorderForEdgeAt(rowIndex, colIndex);
+        ComputeTopBorderForEdgeAt(aPresContext, rowIndex, colIndex);
       }
-      ComputeBottomBorderForEdgeAt(rowIndex, colIndex);
+      ComputeBottomBorderForEdgeAt(aPresContext, rowIndex, colIndex);
     }
   }
 }
 
 /* compute the vertical collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-void nsTableFrame::ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex,
+void nsTableFrame::ComputeVerticalCollapsingBorders(nsIPresContext& aPresContext,
+                                                    PRInt32 aStartRowIndex,
                                                     PRInt32 aEndRowIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
@@ -1244,14 +1246,16 @@ void nsTableFrame::ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex,
     {
       if (0==colIndex)
       { // table is left neighbor
-        ComputeLeftBorderForEdgeAt(rowIndex, colIndex);
+        ComputeLeftBorderForEdgeAt(aPresContext, rowIndex, colIndex);
       }
-      ComputeRightBorderForEdgeAt(rowIndex, colIndex);
+      ComputeRightBorderForEdgeAt(aPresContext, rowIndex, colIndex);
     }
   }
 }
 
-void nsTableFrame::ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeLeftBorderForEdgeAt(nsIPresContext& aPresContext,
+                                              PRInt32 aRowIndex, 
+                                              PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 numSegments = mBorderEdges.mEdges[NS_SIDE_LEFT].Count();
@@ -1302,19 +1306,30 @@ void nsTableFrame::ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColInd
   }
   ComputeCollapsedBorderSegment(NS_SIDE_LEFT, &styles, *border, PR_FALSE);
   // now give half the computed border to the table segment, and half to the cell
-  // XXX give half to the cell
-  border->mWidth = (border->mWidth)/2;
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the table border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border->mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border->mWidth = widthAsPixels/2;
+  if ((border->mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border->mWidth *= NSToCoordCeil(p2t);
   border->mLength = rowRect.height;
-  mBorderEdges.mMaxBorderWidth.left = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.left);
   printf("table computed left border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border->mWidth, border->mLength, border->mColor, border->mStyle, mBorderEdges.mMaxBorderWidth.left);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, border);  // set the left edge of the cell frame
+    cellFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, border, 0);  // set the left edge of the cell frame
   }
+  border->mWidth += widthToAdd;
+  mBorderEdges.mMaxBorderWidth.left = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.left);
 }
 
-void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeRightBorderForEdgeAt(nsIPresContext& aPresContext,
+                                               PRInt32 aRowIndex, 
+                                               PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 colCount = mCellMap->GetColCount();
@@ -1405,8 +1420,16 @@ void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIn
   ComputeCollapsedBorderSegment(NS_SIDE_RIGHT, &styles, border, PRBool(nsnull!=rightNeighborFrame));
   // now give half the computed border to each of the two neighbors 
   // (the 2 cells, or the cell and the table)
-  // XXX give half to the cell
-  border.mWidth = (border.mWidth)/2;  //XXX: rounding
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right cell border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border.mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border.mWidth = widthAsPixels/2;
+  if ((border.mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border.mWidth *= NSToCoordCeil(p2t);
   border.mLength = rowRect.height;
   if (nsnull==rightNeighborFrame)
   {
@@ -1415,16 +1438,18 @@ void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIn
     mBorderEdges.mMaxBorderWidth.right = PR_MAX(border.mWidth, mBorderEdges.mMaxBorderWidth.right);
   }
   else
-    rightNeighborFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, &border);
+    rightNeighborFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, &border, 0);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_RIGHT, aRowIndex, aColIndex, &border);
+    cellFrame->SetBorderEdge(NS_SIDE_RIGHT, aRowIndex, aColIndex, &border, widthToAdd);
   }
   printf("table computed right border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border.mWidth, border.mLength, border.mColor, border.mStyle, mBorderEdges.mMaxBorderWidth.right);
 }
 
-void nsTableFrame::ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeTopBorderForEdgeAt(nsIPresContext& aPresContext,
+                                             PRInt32 aRowIndex, 
+                                             PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 numSegments = mBorderEdges.mEdges[NS_SIDE_TOP].Count();
@@ -1473,18 +1498,30 @@ void nsTableFrame::ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColInde
   }
   ComputeCollapsedBorderSegment(NS_SIDE_TOP, &styles, *border, PR_FALSE);
   // now give half the computed border to the table segment, and half to the cell
-  border->mWidth = (border->mWidth)/2;
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border->mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border->mWidth = widthAsPixels/2;
+  if ((border->mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border->mWidth *= NSToCoordCeil(p2t);
   border->mLength = GetColumnWidth(aColIndex);
-  mBorderEdges.mMaxBorderWidth.top = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.top);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, border);  // set the top edge of the cell frame
+    cellFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, border, 0);  // set the top edge of the cell frame
   }
+  border->mWidth += widthToAdd;
+  mBorderEdges.mMaxBorderWidth.top = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.top);
   printf("table computed top border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border->mWidth, border->mLength, border->mColor, border->mStyle, mBorderEdges.mMaxBorderWidth.top);
 }
 
-void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeBottomBorderForEdgeAt(nsIPresContext& aPresContext,
+                                                PRInt32 aRowIndex, 
+                                                PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 rowCount = mCellMap->GetRowCount();
@@ -1575,8 +1612,16 @@ void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColI
   ComputeCollapsedBorderSegment(NS_SIDE_BOTTOM, &styles, border, PRBool(nsnull!=bottomNeighborFrame));
   // now give half the computed border to each of the two neighbors 
   // (the 2 cells, or the cell and the table)
-  // XXX give half to the cell
-  border.mWidth = (border.mWidth)/2;  //XXX: rounding
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right cell border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border.mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border.mWidth = widthAsPixels/2;
+  if ((border.mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border.mWidth *= NSToCoordCeil(p2t);
   border.mLength = GetColumnWidth(aColIndex);
   if (nsnull==bottomNeighborFrame)
   {
@@ -1585,10 +1630,10 @@ void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColI
     mBorderEdges.mMaxBorderWidth.bottom = PR_MAX(border.mWidth, mBorderEdges.mMaxBorderWidth.bottom);
   }
   else
-    bottomNeighborFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, &border);
+    bottomNeighborFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, &border, 0);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_BOTTOM, aRowIndex, aColIndex, &border);
+    cellFrame->SetBorderEdge(NS_SIDE_BOTTOM, aRowIndex, aColIndex, &border, widthToAdd);
   }
   printf("table computed bottom border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border.mWidth, border.mLength, border.mColor, border.mStyle, mBorderEdges.mMaxBorderWidth.bottom);
@@ -1829,7 +1874,7 @@ void nsTableFrame::ComputeCollapsedBorderSegment(PRUint8       aSide,
 
 }
 
-void nsTableFrame::RecalcLayoutData()
+void nsTableFrame::RecalcLayoutData(nsIPresContext& aPresContext)
 {
   nsCellMap *cellMap = GetCellMap();
   if (nsnull==cellMap)
@@ -1842,7 +1887,7 @@ void nsTableFrame::RecalcLayoutData()
   const nsStyleTable *tableStyle=nsnull;
   GetStyleData(eStyleStruct_Table, (const nsStyleStruct *&)tableStyle);
   if (NS_STYLE_BORDER_COLLAPSE==tableStyle->mBorderCollapse)
-    ComputeVerticalCollapsingBorders(0, rowCount-1);
+    ComputeVerticalCollapsingBorders(aPresContext, 0, rowCount-1);
 
   //XXX need to determine how much of what follows is really necessary
   //    it does collapsing margins between table elements
@@ -2247,7 +2292,7 @@ NS_METHOD nsTableFrame::Reflow(nsIPresContext& aPresContext,
     {
       if (PR_TRUE==gsDebug || PR_TRUE==gsDebugIR) printf("TIF Reflow: needs recalc. Calling BuildColumnCache...\n");
       BuildColumnCache(aPresContext, aDesiredSize, aReflowState, aStatus);
-      RecalcLayoutData();  // Recalculate Layout Dependencies
+      RecalcLayoutData(aPresContext);  // Recalculate Layout Dependencies
       // if we needed to rebuild the column cache, the data stored in the layout strategy is invalid
       if (nsnull!=mTableLayoutStrategy)
       {
@@ -3467,7 +3512,7 @@ void nsTableFrame::BalanceColumnWidths(nsIPresContext& aPresContext,
   mColumnWidthsSet=PR_TRUE;
   if (NS_STYLE_BORDER_COLLAPSE==tableStyle->mBorderCollapse)
   {
-    ComputeHorizontalCollapsingBorders(0, mCellMap->GetRowCount()-1);
+    ComputeHorizontalCollapsingBorders(aPresContext, 0, mCellMap->GetRowCount()-1);
   }
 }
 

layout/html/table/src/nsTableFrame.h

@@ -211,15 +211,27 @@ public:
   void    AppendLayoutData(nsVoidArray* aList, nsTableCellFrame* aTableCell);
 
   /** compute the left and right collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-  void    ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex, PRInt32 aEndRowIndex);
+  void    ComputeVerticalCollapsingBorders(nsIPresContext& aPresContext,
+                                           PRInt32 aStartRowIndex, 
+                                           PRInt32 aEndRowIndex);
 
   /** compute the top and bottom collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-  void    ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex, PRInt32 aEndRowIndex);
+  void    ComputeHorizontalCollapsingBorders(nsIPresContext& aPresContext,
+                                             PRInt32 aStartRowIndex, 
+                                             PRInt32 aEndRowIndex);
 
-  void    ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
+  void    ComputeLeftBorderForEdgeAt(nsIPresContext& aPresContext,
+                                     PRInt32 aRowIndex, 
+                                     PRInt32 aColIndex);
+  void    ComputeRightBorderForEdgeAt(nsIPresContext& aPresContext,
+                                      PRInt32 aRowIndex, 
+                                      PRInt32 aColIndex);
+  void    ComputeTopBorderForEdgeAt(nsIPresContext& aPresContext,
+                                    PRInt32 aRowIndex, 
+                                    PRInt32 aColIndex);
+  void    ComputeBottomBorderForEdgeAt(nsIPresContext& aPresContext,
+                                       PRInt32 aRowIndex, 
+                                       PRInt32 aColIndex);
   
   /** at the time we initially compute collapsing borders, we don't yet have the 
     * column widths.  So we set them as a post-process of the column balancing algorithm.
@@ -240,7 +252,7 @@ public:
                                         PRBool        aFlipLastSide);
 
 
-  void    RecalcLayoutData();
+  void    RecalcLayoutData(nsIPresContext& aPresContext);
 
   // Get cell margin information
   NS_IMETHOD GetCellMarginData(nsTableCellFrame* aKidFrame, nsMargin& aMargin);

layout/tables/nsTableCellFrame.cpp

@@ -82,7 +82,9 @@ void nsTableCellFrame::InitCellFrame(PRInt32 aColIndex)
   }
 }
 
-void nsTableCellFrame::SetBorderEdgeLength(PRUint8 aSide, PRInt32 aIndex, nscoord aLength)
+void nsTableCellFrame::SetBorderEdgeLength(PRUint8 aSide, 
+                                           PRInt32 aIndex, 
+                                           nscoord aLength)
 {
   if ((NS_SIDE_LEFT==aSide) || (NS_SIDE_RIGHT==aSide))
   {
@@ -177,7 +179,8 @@ nsTableCellFrame::GetSkipSides() const
 void nsTableCellFrame::SetBorderEdge(PRUint8       aSide, 
                                      PRInt32       aRowIndex, 
                                      PRInt32       aColIndex, 
-                                     nsBorderEdge *aBorder)
+                                     nsBorderEdge *aBorder,
+                                     nscoord       aOddAmountToAdd)
 {
   nsBorderEdge *border = nsnull;
   switch (aSide)
@@ -216,6 +219,7 @@ void nsTableCellFrame::SetBorderEdge(PRUint8       aSide,
   }
   if (nsnull!=border) {
     *border=*aBorder;
+    border->mWidth += aOddAmountToAdd;
   }
   else {
     NS_ASSERTION(PR_FALSE, "bad border edge state");

layout/tables/nsTableCellFrame.h

@@ -44,7 +44,8 @@ public:
   void SetBorderEdge(PRUint8 aSide, 
                      PRInt32 aRowIndex, 
                      PRInt32 aColIndex, 
-                     nsBorderEdge *border);
+                     nsBorderEdge *border,
+                     nscoord aOddAmountToAdd);
 
   void SetBorderEdgeLength(PRUint8 aSide, 
                            PRInt32 aIndex, 

layout/tables/nsTableFrame.cpp

@@ -1196,7 +1196,8 @@ void nsTableFrame::SetBorderEdgeLength(PRUint8 aSide, PRInt32 aIndex, nscoord aL
   // the object on the right/bottom gets the extra portion
 
 /* compute the horizontal collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-void nsTableFrame::ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex,
+void nsTableFrame::ComputeHorizontalCollapsingBorders(nsIPresContext& aPresContext,
+                                                      PRInt32 aStartRowIndex,
                                                       PRInt32 aEndRowIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
@@ -1216,15 +1217,16 @@ void nsTableFrame::ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex,
     {
       if (0==rowIndex)
       { // table is top neighbor
-        ComputeTopBorderForEdgeAt(rowIndex, colIndex);
+        ComputeTopBorderForEdgeAt(aPresContext, rowIndex, colIndex);
       }
-      ComputeBottomBorderForEdgeAt(rowIndex, colIndex);
+      ComputeBottomBorderForEdgeAt(aPresContext, rowIndex, colIndex);
     }
   }
 }
 
 /* compute the vertical collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-void nsTableFrame::ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex,
+void nsTableFrame::ComputeVerticalCollapsingBorders(nsIPresContext& aPresContext,
+                                                    PRInt32 aStartRowIndex,
                                                     PRInt32 aEndRowIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
@@ -1244,14 +1246,16 @@ void nsTableFrame::ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex,
     {
       if (0==colIndex)
       { // table is left neighbor
-        ComputeLeftBorderForEdgeAt(rowIndex, colIndex);
+        ComputeLeftBorderForEdgeAt(aPresContext, rowIndex, colIndex);
       }
-      ComputeRightBorderForEdgeAt(rowIndex, colIndex);
+      ComputeRightBorderForEdgeAt(aPresContext, rowIndex, colIndex);
     }
   }
 }
 
-void nsTableFrame::ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeLeftBorderForEdgeAt(nsIPresContext& aPresContext,
+                                              PRInt32 aRowIndex, 
+                                              PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 numSegments = mBorderEdges.mEdges[NS_SIDE_LEFT].Count();
@@ -1302,19 +1306,30 @@ void nsTableFrame::ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColInd
   }
   ComputeCollapsedBorderSegment(NS_SIDE_LEFT, &styles, *border, PR_FALSE);
   // now give half the computed border to the table segment, and half to the cell
-  // XXX give half to the cell
-  border->mWidth = (border->mWidth)/2;
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the table border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border->mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border->mWidth = widthAsPixels/2;
+  if ((border->mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border->mWidth *= NSToCoordCeil(p2t);
   border->mLength = rowRect.height;
-  mBorderEdges.mMaxBorderWidth.left = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.left);
   printf("table computed left border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border->mWidth, border->mLength, border->mColor, border->mStyle, mBorderEdges.mMaxBorderWidth.left);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, border);  // set the left edge of the cell frame
+    cellFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, border, 0);  // set the left edge of the cell frame
   }
+  border->mWidth += widthToAdd;
+  mBorderEdges.mMaxBorderWidth.left = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.left);
 }
 
-void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeRightBorderForEdgeAt(nsIPresContext& aPresContext,
+                                               PRInt32 aRowIndex, 
+                                               PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 colCount = mCellMap->GetColCount();
@@ -1405,8 +1420,16 @@ void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIn
   ComputeCollapsedBorderSegment(NS_SIDE_RIGHT, &styles, border, PRBool(nsnull!=rightNeighborFrame));
   // now give half the computed border to each of the two neighbors 
   // (the 2 cells, or the cell and the table)
-  // XXX give half to the cell
-  border.mWidth = (border.mWidth)/2;  //XXX: rounding
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right cell border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border.mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border.mWidth = widthAsPixels/2;
+  if ((border.mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border.mWidth *= NSToCoordCeil(p2t);
   border.mLength = rowRect.height;
   if (nsnull==rightNeighborFrame)
   {
@@ -1415,16 +1438,18 @@ void nsTableFrame::ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIn
     mBorderEdges.mMaxBorderWidth.right = PR_MAX(border.mWidth, mBorderEdges.mMaxBorderWidth.right);
   }
   else
-    rightNeighborFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, &border);
+    rightNeighborFrame->SetBorderEdge(NS_SIDE_LEFT, aRowIndex, aColIndex, &border, 0);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_RIGHT, aRowIndex, aColIndex, &border);
+    cellFrame->SetBorderEdge(NS_SIDE_RIGHT, aRowIndex, aColIndex, &border, widthToAdd);
   }
   printf("table computed right border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border.mWidth, border.mLength, border.mColor, border.mStyle, mBorderEdges.mMaxBorderWidth.right);
 }
 
-void nsTableFrame::ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeTopBorderForEdgeAt(nsIPresContext& aPresContext,
+                                             PRInt32 aRowIndex, 
+                                             PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 numSegments = mBorderEdges.mEdges[NS_SIDE_TOP].Count();
@@ -1473,18 +1498,30 @@ void nsTableFrame::ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColInde
   }
   ComputeCollapsedBorderSegment(NS_SIDE_TOP, &styles, *border, PR_FALSE);
   // now give half the computed border to the table segment, and half to the cell
-  border->mWidth = (border->mWidth)/2;
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border->mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border->mWidth = widthAsPixels/2;
+  if ((border->mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border->mWidth *= NSToCoordCeil(p2t);
   border->mLength = GetColumnWidth(aColIndex);
-  mBorderEdges.mMaxBorderWidth.top = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.top);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, border);  // set the top edge of the cell frame
+    cellFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, border, 0);  // set the top edge of the cell frame
   }
+  border->mWidth += widthToAdd;
+  mBorderEdges.mMaxBorderWidth.top = PR_MAX(border->mWidth, mBorderEdges.mMaxBorderWidth.top);
   printf("table computed top border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border->mWidth, border->mLength, border->mColor, border->mStyle, mBorderEdges.mMaxBorderWidth.top);
 }
 
-void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex)
+void nsTableFrame::ComputeBottomBorderForEdgeAt(nsIPresContext& aPresContext,
+                                                PRInt32 aRowIndex, 
+                                                PRInt32 aColIndex)
 {
   // this method just uses mCellMap, because it can't get called unless nCellMap!=nsnull
   PRInt32 rowCount = mCellMap->GetRowCount();
@@ -1575,8 +1612,16 @@ void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColI
   ComputeCollapsedBorderSegment(NS_SIDE_BOTTOM, &styles, border, PRBool(nsnull!=bottomNeighborFrame));
   // now give half the computed border to each of the two neighbors 
   // (the 2 cells, or the cell and the table)
-  // XXX give half to the cell
-  border.mWidth = (border.mWidth)/2;  //XXX: rounding
+  // to avoid rounding errors, we convert up to pixels, divide by 2, and 
+  // we give the odd pixel to the right cell border
+  float t2p = aPresContext.GetTwipsToPixels();
+  float p2t = aPresContext.GetPixelsToTwips();
+  nscoord widthAsPixels = NSToCoordRound((float)(border.mWidth)*t2p);
+  nscoord widthToAdd = 0;
+  border.mWidth = widthAsPixels/2;
+  if ((border.mWidth*2)!=widthAsPixels)
+    widthToAdd = NSToCoordCeil(p2t);
+  border.mWidth *= NSToCoordCeil(p2t);
   border.mLength = GetColumnWidth(aColIndex);
   if (nsnull==bottomNeighborFrame)
   {
@@ -1585,10 +1630,10 @@ void nsTableFrame::ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColI
     mBorderEdges.mMaxBorderWidth.bottom = PR_MAX(border.mWidth, mBorderEdges.mMaxBorderWidth.bottom);
   }
   else
-    bottomNeighborFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, &border);
+    bottomNeighborFrame->SetBorderEdge(NS_SIDE_TOP, aRowIndex, aColIndex, &border, 0);
   if (nsnull!=cellFrame)
   {
-    cellFrame->SetBorderEdge(NS_SIDE_BOTTOM, aRowIndex, aColIndex, &border);
+    cellFrame->SetBorderEdge(NS_SIDE_BOTTOM, aRowIndex, aColIndex, &border, widthToAdd);
   }
   printf("table computed bottom border width=%d length=%d, color=%d style=%d maxWidth=%d \n",
           border.mWidth, border.mLength, border.mColor, border.mStyle, mBorderEdges.mMaxBorderWidth.bottom);
@@ -1829,7 +1874,7 @@ void nsTableFrame::ComputeCollapsedBorderSegment(PRUint8       aSide,
 
 }
 
-void nsTableFrame::RecalcLayoutData()
+void nsTableFrame::RecalcLayoutData(nsIPresContext& aPresContext)
 {
   nsCellMap *cellMap = GetCellMap();
   if (nsnull==cellMap)
@@ -1842,7 +1887,7 @@ void nsTableFrame::RecalcLayoutData()
   const nsStyleTable *tableStyle=nsnull;
   GetStyleData(eStyleStruct_Table, (const nsStyleStruct *&)tableStyle);
   if (NS_STYLE_BORDER_COLLAPSE==tableStyle->mBorderCollapse)
-    ComputeVerticalCollapsingBorders(0, rowCount-1);
+    ComputeVerticalCollapsingBorders(aPresContext, 0, rowCount-1);
 
   //XXX need to determine how much of what follows is really necessary
   //    it does collapsing margins between table elements
@@ -2247,7 +2292,7 @@ NS_METHOD nsTableFrame::Reflow(nsIPresContext& aPresContext,
     {
       if (PR_TRUE==gsDebug || PR_TRUE==gsDebugIR) printf("TIF Reflow: needs recalc. Calling BuildColumnCache...\n");
       BuildColumnCache(aPresContext, aDesiredSize, aReflowState, aStatus);
-      RecalcLayoutData();  // Recalculate Layout Dependencies
+      RecalcLayoutData(aPresContext);  // Recalculate Layout Dependencies
       // if we needed to rebuild the column cache, the data stored in the layout strategy is invalid
       if (nsnull!=mTableLayoutStrategy)
       {
@@ -3467,7 +3512,7 @@ void nsTableFrame::BalanceColumnWidths(nsIPresContext& aPresContext,
   mColumnWidthsSet=PR_TRUE;
   if (NS_STYLE_BORDER_COLLAPSE==tableStyle->mBorderCollapse)
   {
-    ComputeHorizontalCollapsingBorders(0, mCellMap->GetRowCount()-1);
+    ComputeHorizontalCollapsingBorders(aPresContext, 0, mCellMap->GetRowCount()-1);
   }
 }
 

layout/tables/nsTableFrame.h

@@ -211,15 +211,27 @@ public:
   void    AppendLayoutData(nsVoidArray* aList, nsTableCellFrame* aTableCell);
 
   /** compute the left and right collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-  void    ComputeVerticalCollapsingBorders(PRInt32 aStartRowIndex, PRInt32 aEndRowIndex);
+  void    ComputeVerticalCollapsingBorders(nsIPresContext& aPresContext,
+                                           PRInt32 aStartRowIndex, 
+                                           PRInt32 aEndRowIndex);
 
   /** compute the top and bottom collapsed borders between aStartRowIndex and aEndRowIndex, inclusive */
-  void    ComputeHorizontalCollapsingBorders(PRInt32 aStartRowIndex, PRInt32 aEndRowIndex);
+  void    ComputeHorizontalCollapsingBorders(nsIPresContext& aPresContext,
+                                             PRInt32 aStartRowIndex, 
+                                             PRInt32 aEndRowIndex);
 
-  void    ComputeLeftBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeRightBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeTopBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
-  void    ComputeBottomBorderForEdgeAt(PRInt32 aRowIndex, PRInt32 aColIndex);
+  void    ComputeLeftBorderForEdgeAt(nsIPresContext& aPresContext,
+                                     PRInt32 aRowIndex, 
+                                     PRInt32 aColIndex);
+  void    ComputeRightBorderForEdgeAt(nsIPresContext& aPresContext,
+                                      PRInt32 aRowIndex, 
+                                      PRInt32 aColIndex);
+  void    ComputeTopBorderForEdgeAt(nsIPresContext& aPresContext,
+                                    PRInt32 aRowIndex, 
+                                    PRInt32 aColIndex);
+  void    ComputeBottomBorderForEdgeAt(nsIPresContext& aPresContext,
+                                       PRInt32 aRowIndex, 
+                                       PRInt32 aColIndex);
   
   /** at the time we initially compute collapsing borders, we don't yet have the 
     * column widths.  So we set them as a post-process of the column balancing algorithm.
@@ -240,7 +252,7 @@ public:
                                         PRBool        aFlipLastSide);
 
 
-  void    RecalcLayoutData();
+  void    RecalcLayoutData(nsIPresContext& aPresContext);
 
   // Get cell margin information
   NS_IMETHOD GetCellMarginData(nsTableCellFrame* aKidFrame, nsMargin& aMargin);