Fix app-unit rounding for border width edges

layout/style/nsRuleNode.cpp

@@ -319,6 +319,11 @@ nsRuleNode::EnsureInlineDisplay(StyleDisplay& display)
   }
 }
 
+enum class AppUnitRounding {
+  Default,
+  TowardZero
+};
+
 static nscoord CalcLengthWith(const nsCSSValue& aValue,
                               nscoord aFontSize,
                               const nsStyleFont* aStyleFont,
@@ -326,7 +331,9 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
                               nsPresContext* aPresContext,
                               bool aUseProvidedRootEmSize,
                               bool aUseUserFontSet,
-                              RuleNodeCacheConditions& aConditions);
+                              RuleNodeCacheConditions& aConditions,
+                              AppUnitRounding aRounding =
+                                AppUnitRounding::Default);
 
 struct CalcLengthCalcOps : public css::BasicCoordCalcOps,
                            public css::NumbersAlreadyNormalizedOps
@@ -339,18 +346,21 @@ struct CalcLengthCalcOps : public css::BasicCoordCalcOps,
   const bool mUseProvidedRootEmSize;
   const bool mUseUserFontSet;
   RuleNodeCacheConditions& mConditions;
+  const AppUnitRounding mRounding;
 
   CalcLengthCalcOps(nscoord aFontSize, const nsStyleFont* aStyleFont,
                     nsStyleContext* aStyleContext, nsPresContext* aPresContext,
                     bool aUseProvidedRootEmSize, bool aUseUserFontSet,
-                    RuleNodeCacheConditions& aConditions)
+                    RuleNodeCacheConditions& aConditions,
+                    AppUnitRounding aRounding)
     : mFontSize(aFontSize),
       mStyleFont(aStyleFont),
       mStyleContext(aStyleContext),
       mPresContext(aPresContext),
       mUseProvidedRootEmSize(aUseProvidedRootEmSize),
       mUseUserFontSet(aUseUserFontSet),
-      mConditions(aConditions)
+      mConditions(aConditions),
+      mRounding(aRounding)
   {
   }
 
@@ -358,15 +368,84 @@ struct CalcLengthCalcOps : public css::BasicCoordCalcOps,
   {
     return CalcLengthWith(aValue, mFontSize, mStyleFont,
                           mStyleContext, mPresContext, mUseProvidedRootEmSize,
-                          mUseUserFontSet, mConditions);
+                          mUseUserFontSet, mConditions, mRounding);
   }
 };
 
-static inline nscoord ScaleCoordRound(const nsCSSValue& aValue, float aFactor)
+static inline nscoord
+ScaleCoordWithRounding(const nsCSSValue& aValue, float aFactor,
+                       AppUnitRounding aRounding)
 {
+  if (aRounding == AppUnitRounding::TowardZero) {
+    return NSToCoordTruncClamped(aValue.GetFloatValue() * aFactor);
+  }
   return NSToCoordRoundWithClamp(aValue.GetFloatValue() * aFactor);
 }
 
+static inline nscoord
+CSSPixelsToAppUnitsWithRounding(float aPixels, AppUnitRounding aRounding)
+{
+  if (aRounding == AppUnitRounding::TowardZero) {
+    return NSToCoordTruncClamped(double(aPixels) *
+                                 nsPresContext::AppUnitsPerCSSPixel());
+  }
+  return nsPresContext::CSSPixelsToAppUnits(aPixels);
+}
+
+static nscoord
+GetFixedLengthWithRounding(const nsCSSValue& aValue,
+                           nsPresContext* aPresContext,
+                           AppUnitRounding aRounding)
+{
+  if (aRounding == AppUnitRounding::Default) {
+    return aValue.GetFixedLength(aPresContext);
+  }
+
+  MOZ_ASSERT(aValue.GetUnit() == eCSSUnit_PhysicalMillimeter,
+             "not a fixed length unit");
+  double inches = double(aValue.GetFloatValue()) / MM_PER_INCH_FLOAT;
+  return NSToCoordTruncClamped(
+    inches * aPresContext->DeviceContext()->AppUnitsPerPhysicalInch());
+}
+
+static nscoord
+GetPixelLengthWithRounding(const nsCSSValue& aValue,
+                           AppUnitRounding aRounding)
+{
+  MOZ_ASSERT(aValue.IsPixelLengthUnit(), "not a pixel length unit");
+
+  double scaleFactor;
+  switch (aValue.GetUnit()) {
+    case eCSSUnit_Pixel:
+      return CSSPixelsToAppUnitsWithRounding(aValue.GetFloatValue(),
+                                             aRounding);
+    case eCSSUnit_Pica:
+      scaleFactor = 16.0;
+      break;
+    case eCSSUnit_Point:
+      scaleFactor = 4.0 / 3.0;
+      break;
+    case eCSSUnit_Inch:
+      scaleFactor = 96.0;
+      break;
+    case eCSSUnit_Millimeter:
+      scaleFactor = 96.0 / 25.4;
+      break;
+    case eCSSUnit_Centimeter:
+      scaleFactor = 96.0 / 2.54;
+      break;
+    case eCSSUnit_Quarter:
+      scaleFactor = 96.0 / 101.6;
+      break;
+    default:
+      NS_ERROR("should never get here");
+      return 0;
+  }
+
+  return CSSPixelsToAppUnitsWithRounding(
+    float(double(aValue.GetFloatValue()) * scaleFactor), aRounding);
+}
+
 static inline nscoord ScaleViewportCoordTrunc(const nsCSSValue& aValue,
                                               nscoord aViewportSize)
 {
@@ -465,7 +544,8 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
                               // except when called from
                               // CalcLengthWithInitialFont.
                               bool aUseUserFontSet,
-                              RuleNodeCacheConditions& aConditions)
+                              RuleNodeCacheConditions& aConditions,
+                              AppUnitRounding aRounding)
 {
   NS_ASSERTION(aValue.IsLengthUnit() || aValue.IsCalcUnit(),
                "not a length or calc unit");
@@ -476,10 +556,10 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
   NS_ASSERTION(aPresContext, "Must have prescontext");
 
   if (aValue.IsFixedLengthUnit()) {
-    return aValue.GetFixedLength(aPresContext);
+    return GetFixedLengthWithRounding(aValue, aPresContext, aRounding);
   }
   if (aValue.IsPixelLengthUnit()) {
-    return aValue.GetPixelLength();
+    return GetPixelLengthWithRounding(aValue, aRounding);
   }
   if (aValue.IsCalcUnit()) {
     // For properties for which lengths are the *only* units accepted in
@@ -490,7 +570,7 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
     CalcLengthCalcOps ops(aFontSize, aStyleFont,
                           aStyleContext, aPresContext,
                           aUseProvidedRootEmSize, aUseUserFontSet,
-                          aConditions);
+                          aConditions, aRounding);
     return css::ComputeCalc(aValue, ops);
   }
   switch (aValue.GetUnit()) {
@@ -623,7 +703,7 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
         rootFontSize = rootStyleFont->mFont.size;
       }
 
-      return ScaleCoordRound(aValue, float(rootFontSize));
+      return ScaleCoordWithRounding(aValue, float(rootFontSize), aRounding);
     }
     default:
       // Fall through to the code for units that can't be stored in the
@@ -648,7 +728,7 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
       // CSS2.1 specifies that this unit scales to the computed font
       // size, not the em-width in the font metrics, despite the name.
       aConditions.SetFontSizeDependency(aFontSize);
-      return ScaleCoordRound(aValue, float(aFontSize));
+      return ScaleCoordWithRounding(aValue, float(aFontSize), aRounding);
     }
     case eCSSUnit_XHeight: {
       aPresContext->SetUsesExChUnits(true);
@@ -656,7 +736,7 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
         GetMetricsFor(aPresContext, aStyleContext, styleFont,
                       aFontSize, aUseUserFontSet);
       aConditions.SetUncacheable();
-      return ScaleCoordRound(aValue, float(fm->XHeight()));
+      return ScaleCoordWithRounding(aValue, float(fm->XHeight()), aRounding);
     }
     case eCSSUnit_Char: {
       aPresContext->SetUsesExChUnits(true);
@@ -668,8 +748,9 @@ static nscoord CalcLengthWith(const nsCSSValue& aValue,
           GetMetrics(fm->Orientation()).zeroOrAveCharWidth;
 
       aConditions.SetUncacheable();
-      return ScaleCoordRound(aValue, ceil(aPresContext->AppUnitsPerDevPixel() *
+      return ScaleCoordWithRounding(
-                                          zeroWidth));
+        aValue, ceil(aPresContext->AppUnitsPerDevPixel() * zeroWidth),
+        aRounding);
     }
     default:
       NS_NOTREACHED("unexpected unit");
@@ -701,6 +782,20 @@ static inline nscoord CalcLength(const nsCSSValue& aValue,
                                 aPresContext, aConditions);
 }
 
+static inline nscoord
+CalcLengthTowardZero(const nsCSSValue& aValue,
+                     nsStyleContext* aStyleContext,
+                     nsPresContext* aPresContext,
+                     RuleNodeCacheConditions& aConditions)
+{
+  NS_ASSERTION(aStyleContext, "Must have style data");
+
+  return CalcLengthWith(aValue, -1, nullptr,
+                        aStyleContext, aPresContext,
+                        false, true, aConditions,
+                        AppUnitRounding::TowardZero);
+}
+
 /* static */ nscoord
 nsRuleNode::CalcLengthWithInitialFont(nsPresContext* aPresContext,
                                       const nsCSSValue& aValue)
@@ -8048,13 +8143,11 @@ nsRuleNode::ComputeBorderData(void* aStartStruct,
                      "Unexpected enum value");
         border->SetBorderWidth(side,
                                (mPresContext->GetBorderWidthTable())[value.GetIntValue()]);
-      // OK to pass bad aParentCoord since we're not passing SETCOORD_INHERIT
+      } else if (value.IsLengthUnit() || value.IsCalcUnit()) {
-      } else if (SetCoord(value, coord, nsStyleCoord(),
-                        SETCOORD_LENGTH | SETCOORD_CALC_LENGTH_ONLY,
-                        aContext, mPresContext, conditions)) {
-        NS_ASSERTION(coord.GetUnit() == eStyleUnit_Coord, "unexpected unit");
         // clamp negative calc() to 0.
-        border->SetBorderWidth(side, std::max(coord.GetCoordValue(), 0));
+        border->SetBorderWidth(side,
+          std::max(CalcLengthTowardZero(value, aContext, mPresContext,
+                                        conditions), 0));
       } else if (eCSSUnit_Inherit == value.GetUnit()) {
         conditions.SetUncacheable();
         border->SetBorderWidth(side,
@@ -8336,6 +8429,11 @@ nsRuleNode::ComputeOutlineData(void* aStartStruct,
       eCSSUnit_Revert == outlineWidthValue->GetUnit()) {
     outline->mOutlineWidth =
       nsStyleCoord(NS_STYLE_BORDER_WIDTH_MEDIUM, eStyleUnit_Enumerated);
+  } else if (outlineWidthValue->IsLengthUnit() ||
+             outlineWidthValue->IsCalcUnit()) {
+    outline->mOutlineWidth.SetCoordValue(
+      CalcLengthTowardZero(*outlineWidthValue, aContext, mPresContext,
+                           conditions));
   } else {
     SetCoord(*outlineWidthValue, outline->mOutlineWidth,
              parentOutline->mOutlineWidth,
@@ -8346,7 +8444,13 @@ nsRuleNode::ComputeOutlineData(void* aStartStruct,
   // outline-offset: length, inherit
   nsStyleCoord tempCoord;
   const nsCSSValue* outlineOffsetValue = aRuleData->ValueForOutlineOffset();
-  if (SetCoord(*outlineOffsetValue, tempCoord,
+  if (outlineOffsetValue->IsLengthUnit() || outlineOffsetValue->IsCalcUnit()) {
+    outline->mOutlineOffset =
+      NS_ROUND_OFFSET_TO_PIXELS(
+        CalcLengthTowardZero(*outlineOffsetValue, aContext, mPresContext,
+                             conditions),
+        mPresContext->AppUnitsPerDevPixel());
+  } else if (SetCoord(*outlineOffsetValue, tempCoord,
                nsStyleCoord(parentOutline->mOutlineOffset,
                             nsStyleCoord::CoordConstructor),
                SETCOORD_LH | SETCOORD_INITIAL_ZERO | SETCOORD_CALC_LENGTH_ONLY |

layout/style/test/test_border_width_rounding.html

@@ -24,6 +24,8 @@ var tests = [
   ["2px", "2px"],
   ["2.75px", "2px"],
   ["2.999px", "2px"],
+  ["3px", "3px"],
+  ["3.001px", "3px"],
 ];
 
 function checkWidth(property, setupProperty, setupValue) {