Make font-size:larger and font-size:smaller smarter about interpolating and

extrapolating font sizes.  Bug 72164, patch by Eric Lawrence
<elawrenc69@yahoo.com>, r=bzbarsky, r+sr=dbaron, a=asa

content/base/src/nsRuleNode.cpp

@@ -1982,41 +1982,15 @@ SetFont(nsIPresContext* aPresContext, nsStyleContext* aContext,
           nsStyleFont::UnZoomText(aPresContext, aParentFont->mSize);
 
       if (NS_STYLE_FONT_SIZE_LARGER == value) {
-        PRInt32 index = nsStyleUtil::FindNextLargerFontSize(parentSize, (PRInt32)aDefaultFont.size,
+        aFont->mSize = nsStyleUtil::FindNextLargerFontSize(parentSize, (PRInt32)aDefaultFont.size,
+                                                           scaleFactor, aPresContext, eFontSize_CSS);
+        NS_ASSERTION(aFont->mSize > parentSize, "FindNextLargerFontSize failed.");
+      } 
+      else {
+        aFont->mSize = nsStyleUtil::FindNextSmallerFontSize(parentSize, (PRInt32)aDefaultFont.size,
                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        nscoord largerSize = nsStyleUtil::CalcFontPointSize(index, (PRInt32)aDefaultFont.size,
+        NS_ASSERTION(aFont->mSize < parentSize, 
-                                                            scaleFactor, aPresContext, eFontSize_CSS);
+            "FindNextSmallerFontSize failed; this is expected if parentFont size <= 1px");
-        aFont->mSize = PR_MAX(largerSize, aParentFont->mSize);
-        if (index == 6 &&
-            aFont->mSize == aParentFont->mSize) {
-          // 6 is the maximal answer from nsStyleUtil::FindNextLargerFontSize
-          // when eFontSize_CSS parameter is passed; we reached the limit for
-          // CSS named sizes, let's apply a %age.
-          // 150% is more or less the ratio between xx-large and x-large in
-          // all tables defined in nsStyleUtil.cpp
-          aFont->mSize = (nscoord)((float)(aParentFont->mSize) * 1.5);
-        }
-        else if (index == 0) {
-          largerSize = (nscoord)((float)(aParentFont->mSize) / 0.9);
-          aFont->mSize = PR_MIN(largerSize, aFont->mSize);
-        }
-      } else {
-        PRInt32 index = nsStyleUtil::FindNextSmallerFontSize(parentSize, (PRInt32)aDefaultFont.size,
-                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        nscoord smallerSize = nsStyleUtil::CalcFontPointSize(index, (PRInt32)aDefaultFont.size,
-                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        aFont->mSize = PR_MIN(smallerSize, aParentFont->mSize);
-        if (index == 0 &&
-            aFont->mSize == aParentFont->mSize) {
-          // 0 is the miminal answer from nsStyleUtil::FindNextLargerFontSize
-          // when eFontSize_CSS parameter is passed; we reached the limit for
-          // CSS named sizes, let's apply a %age
-          aFont->mSize = (nscoord)((float)(aParentFont->mSize) * 0.9);
-        }
-        else if (index == 6) {
-          smallerSize = (nscoord)((float)(aParentFont->mSize) / 1.5);
-          aFont->mSize = PR_MAX(smallerSize, aFont->mSize);
-        }
       }
     } else {
       NS_NOTREACHED("unexpected value");

content/html/style/public/nsStyleUtil.h

@@ -60,11 +60,11 @@ public:
                                    float aScalingFactor, nsIPresContext* aPresContext,
                                    nsFontSizeType aFontSizeType = eFontSize_HTML);
 
-  static PRInt32 FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+  static nscoord FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                          float aScalingFactor, nsIPresContext* aPresContext,
                                          nsFontSizeType aFontSizeType = eFontSize_HTML);
 
-  static PRInt32 FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+  static nscoord FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                         float aScalingFactor, nsIPresContext* aPresContext,
                                         nsFontSizeType aFontSizeType = eFontSize_HTML);
 

content/html/style/src/nsStyleUtil.cpp

@@ -403,20 +403,30 @@ nscoord nsStyleUtil::CalcFontPointSize(PRInt32 aHTMLSize, PRInt32 aBasePointSize
 		return OldCalcFontPointSize(aHTMLSize, aBasePointSize, aScalingFactor);
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------
 
-PRInt32 nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+nscoord nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                              float aScalingFactor, nsIPresContext* aPresContext,
                                              nsFontSizeType aFontSizeType)
 {
   PRInt32 index;
   PRInt32 indexMin;
   PRInt32 indexMax;
-  PRInt32 fontSize = NSTwipsToFloorIntPoints(aFontSize);
+  float relativePosition;
-
+  nscoord smallerSize;
+  nscoord indexFontSize;
+  nscoord smallestIndexFontSize;
+  nscoord largestIndexFontSize;
+  nscoord smallerIndexFontSize;
+  nscoord largerIndexFontSize;
+  float p2t;
+  nscoord onePx;
+  
+  aPresContext->GetPixelsToTwips(&p2t);
+  onePx = NSToCoordRound(p2t);
+    
 	if (aFontSizeType == eFontSize_HTML) {
 		indexMin = 1;
 		indexMax = 7;
@@ -424,46 +434,67 @@ PRInt32 nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePoi
 		indexMin = 0;
 		indexMax = 6;
 	}
-
+  
-  if (NSTwipsToFloorIntPoints(CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)) < fontSize) {
+  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
-    if (fontSize <= NSTwipsToFloorIntPoints(CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType))) { // in HTML table
+  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType); 
-      for (index = indexMax; index > indexMin; index--)
+  if (aFontSize > smallestIndexFontSize) {
-        if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)))
+    if (aFontSize < NSToCoordRound(float(largestIndexFontSize) * 1.5)) { // smaller will be in HTML table
+      // find largest index smaller than current
+      for (index = indexMax; index >= indexMin; index--) {
+        indexFontSize = CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        if (indexFontSize < aFontSize)
           break;
+      } 
+      // set up points beyond table for interpolation purposes
+      if (indexFontSize == smallestIndexFontSize) {
+        smallerIndexFontSize = indexFontSize - onePx;
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      } else if (indexFontSize == largestIndexFontSize) {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = NSToCoordRound(float(largestIndexFontSize) * 1.5);
+      } else {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      }
+      // compute the relative position of the parent size between the two closest indexed sizes
+      relativePosition = float(aFontSize - indexFontSize) / float(largerIndexFontSize - indexFontSize);            
+      // set the new size to have the same relative position between the next smallest two indexed sizes
+      smallerSize = smallerIndexFontSize + NSToCoordRound(relativePosition * (indexFontSize - smallerIndexFontSize));      
     }
-    else {  // larger than HTML table
+    else {  // larger than HTML table, drop by 33%
-      return indexMax;
+      smallerSize = NSToCoordRound(float(aFontSize) / 1.5);
-//    for (index = 8; ; index++)
-//      if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
-//        index--;
-//        break;
-//      }
     }
   }
-  else { // smaller than HTML table
+  else { // smaller than HTML table, drop by 1px
-    return indexMin;
+    smallerSize = PR_MAX(aFontSize - onePx, onePx);
-//  for (index = 0; -25<index ; index--) //prevent infinite loop (bug 17045)
-//    if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
-//      break;
-//    }
   }
-  return index;
+  return smallerSize;
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------
 
-PRInt32 nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+nscoord nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                             float aScalingFactor, nsIPresContext* aPresContext,
                                             nsFontSizeType aFontSizeType)
 {
   PRInt32 index;
   PRInt32 indexMin;
   PRInt32 indexMax;
-  PRInt32 fontSize = NSTwipsToFloorIntPoints(aFontSize);
+  float relativePosition;
-
+  nscoord largerSize;
+  nscoord indexFontSize;
+  nscoord smallestIndexFontSize;
+  nscoord largestIndexFontSize;
+  nscoord smallerIndexFontSize;
+  nscoord largerIndexFontSize;
+  float p2t;
+  nscoord onePx;
+  
+  aPresContext->GetPixelsToTwips(&p2t);
+  onePx = NSToCoordRound(p2t);
+    
 	if (aFontSizeType == eFontSize_HTML) {
 		indexMin = 1;
 		indexMax = 7;
@@ -471,32 +502,45 @@ PRInt32 nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePoin
 		indexMin = 0;
 		indexMax = 6;
 	}
-
+  
-  if (NSTwipsToFloorIntPoints(CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)) <= fontSize) {
+  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
-    if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType))) { // in HTML table
+  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType); 
-      for (index = indexMin; index < indexMax; index++)
+  if (aFontSize > (smallestIndexFontSize - onePx)) {
-        if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)))
+    if (aFontSize < largestIndexFontSize) { // larger will be in HTML table
+      // find smallest index larger than current
+      for (index = indexMin; index <= indexMax; index++) { 
+        indexFontSize = CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        if (indexFontSize > aFontSize)
           break;
+      }
+      // set up points beyond table for interpolation purposes
+      if (indexFontSize == smallestIndexFontSize) {
+        smallerIndexFontSize = indexFontSize - onePx;
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      } else if (indexFontSize == largestIndexFontSize) {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = NSToCoordRound(float(largestIndexFontSize) * 1.5);
+      } else {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      }
+      // compute the relative position of the parent size between the two closest indexed sizes
+      relativePosition = float(aFontSize - smallerIndexFontSize) / float(indexFontSize - smallerIndexFontSize);
+      // set the new size to have the same relative position between the next largest two indexed sizes
+      largerSize = indexFontSize + NSToCoordRound(relativePosition * (largerIndexFontSize - indexFontSize));      
     }
-    else {  // larger than HTML table
+    else {  // larger than HTML table, increase by 50%
-			return indexMax;
+      largerSize = NSToCoordRound(float(aFontSize) * 1.5);
-//    for (index = 8; ; index++)
-//      if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext)))
-//        break;
     }
   }
-  else {  // smaller than HTML table
+  else { // smaller than HTML table, increase by 1px
-    return indexMin;
+    float p2t;
-//  for (index = 0; -25<index ; index--) //prevent infinite loop (bug 17045)
+    aPresContext->GetPixelsToTwips(&p2t);
-//    if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
+    largerSize = aFontSize + NSToCoordRound(p2t); 
-//      index++;
-//      break;
-//    }
   }
-  return index;
+  return largerSize;
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------

layout/style/nsRuleNode.cpp

@@ -1982,41 +1982,15 @@ SetFont(nsIPresContext* aPresContext, nsStyleContext* aContext,
           nsStyleFont::UnZoomText(aPresContext, aParentFont->mSize);
 
       if (NS_STYLE_FONT_SIZE_LARGER == value) {
-        PRInt32 index = nsStyleUtil::FindNextLargerFontSize(parentSize, (PRInt32)aDefaultFont.size,
+        aFont->mSize = nsStyleUtil::FindNextLargerFontSize(parentSize, (PRInt32)aDefaultFont.size,
+                                                           scaleFactor, aPresContext, eFontSize_CSS);
+        NS_ASSERTION(aFont->mSize > parentSize, "FindNextLargerFontSize failed.");
+      } 
+      else {
+        aFont->mSize = nsStyleUtil::FindNextSmallerFontSize(parentSize, (PRInt32)aDefaultFont.size,
                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        nscoord largerSize = nsStyleUtil::CalcFontPointSize(index, (PRInt32)aDefaultFont.size,
+        NS_ASSERTION(aFont->mSize < parentSize, 
-                                                            scaleFactor, aPresContext, eFontSize_CSS);
+            "FindNextSmallerFontSize failed; this is expected if parentFont size <= 1px");
-        aFont->mSize = PR_MAX(largerSize, aParentFont->mSize);
-        if (index == 6 &&
-            aFont->mSize == aParentFont->mSize) {
-          // 6 is the maximal answer from nsStyleUtil::FindNextLargerFontSize
-          // when eFontSize_CSS parameter is passed; we reached the limit for
-          // CSS named sizes, let's apply a %age.
-          // 150% is more or less the ratio between xx-large and x-large in
-          // all tables defined in nsStyleUtil.cpp
-          aFont->mSize = (nscoord)((float)(aParentFont->mSize) * 1.5);
-        }
-        else if (index == 0) {
-          largerSize = (nscoord)((float)(aParentFont->mSize) / 0.9);
-          aFont->mSize = PR_MIN(largerSize, aFont->mSize);
-        }
-      } else {
-        PRInt32 index = nsStyleUtil::FindNextSmallerFontSize(parentSize, (PRInt32)aDefaultFont.size,
-                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        nscoord smallerSize = nsStyleUtil::CalcFontPointSize(index, (PRInt32)aDefaultFont.size,
-                                                             scaleFactor, aPresContext, eFontSize_CSS);
-        aFont->mSize = PR_MIN(smallerSize, aParentFont->mSize);
-        if (index == 0 &&
-            aFont->mSize == aParentFont->mSize) {
-          // 0 is the miminal answer from nsStyleUtil::FindNextLargerFontSize
-          // when eFontSize_CSS parameter is passed; we reached the limit for
-          // CSS named sizes, let's apply a %age
-          aFont->mSize = (nscoord)((float)(aParentFont->mSize) * 0.9);
-        }
-        else if (index == 6) {
-          smallerSize = (nscoord)((float)(aParentFont->mSize) / 1.5);
-          aFont->mSize = PR_MAX(smallerSize, aFont->mSize);
-        }
       }
     } else {
       NS_NOTREACHED("unexpected value");

layout/style/nsStyleUtil.cpp

@@ -403,20 +403,30 @@ nscoord nsStyleUtil::CalcFontPointSize(PRInt32 aHTMLSize, PRInt32 aBasePointSize
 		return OldCalcFontPointSize(aHTMLSize, aBasePointSize, aScalingFactor);
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------
 
-PRInt32 nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+nscoord nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                              float aScalingFactor, nsIPresContext* aPresContext,
                                              nsFontSizeType aFontSizeType)
 {
   PRInt32 index;
   PRInt32 indexMin;
   PRInt32 indexMax;
-  PRInt32 fontSize = NSTwipsToFloorIntPoints(aFontSize);
+  float relativePosition;
-
+  nscoord smallerSize;
+  nscoord indexFontSize;
+  nscoord smallestIndexFontSize;
+  nscoord largestIndexFontSize;
+  nscoord smallerIndexFontSize;
+  nscoord largerIndexFontSize;
+  float p2t;
+  nscoord onePx;
+  
+  aPresContext->GetPixelsToTwips(&p2t);
+  onePx = NSToCoordRound(p2t);
+    
 	if (aFontSizeType == eFontSize_HTML) {
 		indexMin = 1;
 		indexMax = 7;
@@ -424,46 +434,67 @@ PRInt32 nsStyleUtil::FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePoi
 		indexMin = 0;
 		indexMax = 6;
 	}
-
+  
-  if (NSTwipsToFloorIntPoints(CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)) < fontSize) {
+  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
-    if (fontSize <= NSTwipsToFloorIntPoints(CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType))) { // in HTML table
+  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType); 
-      for (index = indexMax; index > indexMin; index--)
+  if (aFontSize > smallestIndexFontSize) {
-        if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)))
+    if (aFontSize < NSToCoordRound(float(largestIndexFontSize) * 1.5)) { // smaller will be in HTML table
+      // find largest index smaller than current
+      for (index = indexMax; index >= indexMin; index--) {
+        indexFontSize = CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        if (indexFontSize < aFontSize)
           break;
+      } 
+      // set up points beyond table for interpolation purposes
+      if (indexFontSize == smallestIndexFontSize) {
+        smallerIndexFontSize = indexFontSize - onePx;
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      } else if (indexFontSize == largestIndexFontSize) {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = NSToCoordRound(float(largestIndexFontSize) * 1.5);
+      } else {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      }
+      // compute the relative position of the parent size between the two closest indexed sizes
+      relativePosition = float(aFontSize - indexFontSize) / float(largerIndexFontSize - indexFontSize);            
+      // set the new size to have the same relative position between the next smallest two indexed sizes
+      smallerSize = smallerIndexFontSize + NSToCoordRound(relativePosition * (indexFontSize - smallerIndexFontSize));      
     }
-    else {  // larger than HTML table
+    else {  // larger than HTML table, drop by 33%
-      return indexMax;
+      smallerSize = NSToCoordRound(float(aFontSize) / 1.5);
-//    for (index = 8; ; index++)
-//      if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
-//        index--;
-//        break;
-//      }
     }
   }
-  else { // smaller than HTML table
+  else { // smaller than HTML table, drop by 1px
-    return indexMin;
+    smallerSize = PR_MAX(aFontSize - onePx, onePx);
-//  for (index = 0; -25<index ; index--) //prevent infinite loop (bug 17045)
-//    if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
-//      break;
-//    }
   }
-  return index;
+  return smallerSize;
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------
 
-PRInt32 nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+nscoord nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                             float aScalingFactor, nsIPresContext* aPresContext,
                                             nsFontSizeType aFontSizeType)
 {
   PRInt32 index;
   PRInt32 indexMin;
   PRInt32 indexMax;
-  PRInt32 fontSize = NSTwipsToFloorIntPoints(aFontSize);
+  float relativePosition;
-
+  nscoord largerSize;
+  nscoord indexFontSize;
+  nscoord smallestIndexFontSize;
+  nscoord largestIndexFontSize;
+  nscoord smallerIndexFontSize;
+  nscoord largerIndexFontSize;
+  float p2t;
+  nscoord onePx;
+  
+  aPresContext->GetPixelsToTwips(&p2t);
+  onePx = NSToCoordRound(p2t);
+    
 	if (aFontSizeType == eFontSize_HTML) {
 		indexMin = 1;
 		indexMax = 7;
@@ -471,32 +502,45 @@ PRInt32 nsStyleUtil::FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePoin
 		indexMin = 0;
 		indexMax = 6;
 	}
-
+  
-  if (NSTwipsToFloorIntPoints(CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)) <= fontSize) {
+  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
-    if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType))) { // in HTML table
+  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType); 
-      for (index = indexMin; index < indexMax; index++)
+  if (aFontSize > (smallestIndexFontSize - onePx)) {
-        if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType)))
+    if (aFontSize < largestIndexFontSize) { // larger will be in HTML table
+      // find smallest index larger than current
+      for (index = indexMin; index <= indexMax; index++) { 
+        indexFontSize = CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        if (indexFontSize > aFontSize)
           break;
+      }
+      // set up points beyond table for interpolation purposes
+      if (indexFontSize == smallestIndexFontSize) {
+        smallerIndexFontSize = indexFontSize - onePx;
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      } else if (indexFontSize == largestIndexFontSize) {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = NSToCoordRound(float(largestIndexFontSize) * 1.5);
+      } else {
+        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aScalingFactor, aPresContext, aFontSizeType);
+      }
+      // compute the relative position of the parent size between the two closest indexed sizes
+      relativePosition = float(aFontSize - smallerIndexFontSize) / float(indexFontSize - smallerIndexFontSize);
+      // set the new size to have the same relative position between the next largest two indexed sizes
+      largerSize = indexFontSize + NSToCoordRound(relativePosition * (largerIndexFontSize - indexFontSize));      
     }
-    else {  // larger than HTML table
+    else {  // larger than HTML table, increase by 50%
-			return indexMax;
+      largerSize = NSToCoordRound(float(aFontSize) * 1.5);
-//    for (index = 8; ; index++)
-//      if (fontSize < NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext)))
-//        break;
     }
   }
-  else {  // smaller than HTML table
+  else { // smaller than HTML table, increase by 1px
-    return indexMin;
+    float p2t;
-//  for (index = 0; -25<index ; index--) //prevent infinite loop (bug 17045)
+    aPresContext->GetPixelsToTwips(&p2t);
-//    if (fontSize > NSTwipsToFloorIntPoints(CalcFontPointSize(index, aBasePointSize, aScalingFactor, aPresContext))) {
+    largerSize = aFontSize + NSToCoordRound(p2t); 
-//      index++;
-//      break;
-//    }
   }
-  return index;
+  return largerSize;
 }
 
-
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------

layout/style/nsStyleUtil.h

@@ -60,11 +60,11 @@ public:
                                    float aScalingFactor, nsIPresContext* aPresContext,
                                    nsFontSizeType aFontSizeType = eFontSize_HTML);
 
-  static PRInt32 FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+  static nscoord FindNextSmallerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                          float aScalingFactor, nsIPresContext* aPresContext,
                                          nsFontSizeType aFontSizeType = eFontSize_HTML);
 
-  static PRInt32 FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
+  static nscoord FindNextLargerFontSize(nscoord aFontSize, PRInt32 aBasePointSize, 
                                         float aScalingFactor, nsIPresContext* aPresContext,
                                         nsFontSizeType aFontSizeType = eFontSize_HTML);