Support CSS sizing math functions

Prereq for parts of #2404

layout/style/CSSCalc.h

@@ -6,6 +6,7 @@
 
 #include "nsCSSValue.h"
 #include "nsStyleCoord.h"
+#include <algorithm>
 #include <math.h>
 
 namespace mozilla {
@@ -46,6 +47,13 @@ namespace css {
  *                        result_type aValue1, float aValue2);
  *
  *   result_type
+ *   MergeMinMax(nsCSSUnit aCalcFunction,
+ *               result_type aValue1, result_type aValue2);
+ *
+ *   result_type
+ *   MergeClamp(result_type aMin, result_type aCenter, result_type aMax);
+ *
+ *   result_type
  *   ComputeLeafValue(const input_type& aValue);
  *
  *   float
@@ -70,6 +78,8 @@ namespace css {
  *   MergeAdditive for Plus and Minus
  *   MergeMultiplicativeL for Times_L (number * value)
  *   MergeMultiplicativeR for Times_R (value * number) and Divided
+ *   MergeMinMax for Min and Max
+ *   MergeClamp for Clamp
  */
 template <class CalcOps>
 static typename CalcOps::result_type
@@ -104,6 +114,25 @@ ComputeCalc(const typename CalcOps::input_type& aValue, CalcOps &aOps)
       float rhs = aOps.ComputeNumber(arr->Item(1));
       return aOps.MergeMultiplicativeR(CalcOps::GetUnit(aValue), lhs, rhs);
     }
+    case eCSSUnit_Calc_Min:
+    case eCSSUnit_Calc_Max: {
+      typename CalcOps::input_array_type *arr = aValue.GetArrayValue();
+      MOZ_ASSERT(arr->Count() >= 1, "unexpected length");
+      typename CalcOps::result_type result = ComputeCalc(arr->Item(0), aOps);
+      for (uint32_t i = 1; i < arr->Count(); ++i) {
+        typename CalcOps::result_type next = ComputeCalc(arr->Item(i), aOps);
+        result = aOps.MergeMinMax(CalcOps::GetUnit(aValue), result, next);
+      }
+      return result;
+    }
+    case eCSSUnit_Calc_Clamp: {
+      typename CalcOps::input_array_type *arr = aValue.GetArrayValue();
+      MOZ_ASSERT(arr->Count() == 3, "unexpected length");
+      typename CalcOps::result_type min = ComputeCalc(arr->Item(0), aOps);
+      typename CalcOps::result_type center = ComputeCalc(arr->Item(1), aOps);
+      typename CalcOps::result_type max = ComputeCalc(arr->Item(2), aOps);
+      return aOps.MergeClamp(min, center, max);
+    }
     default: {
       return aOps.ComputeLeafValue(aValue);
     }
@@ -168,6 +197,23 @@ struct BasicCoordCalcOps
     }
     return NSCoordSaturatingMultiply(aValue1, aValue2);
   }
+
+  result_type
+  MergeMinMax(nsCSSUnit aCalcFunction,
+              result_type aValue1, result_type aValue2)
+  {
+    if (aCalcFunction == eCSSUnit_Calc_Min) {
+      return std::min(aValue1, aValue2);
+    }
+    MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Max, "unexpected unit");
+    return std::max(aValue1, aValue2);
+  }
+
+  result_type
+  MergeClamp(result_type aMin, result_type aCenter, result_type aMax)
+  {
+    return std::max(aMin, std::min(aCenter, aMax));
+  }
 };
 
 struct BasicFloatCalcOps
@@ -206,6 +252,23 @@ struct BasicFloatCalcOps
                "unexpected unit");
     return aValue1 / aValue2;
   }
+
+  result_type
+  MergeMinMax(nsCSSUnit aCalcFunction,
+              result_type aValue1, result_type aValue2)
+  {
+    if (aCalcFunction == eCSSUnit_Calc_Min) {
+      return std::min(aValue1, aValue2);
+    }
+    MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Max, "unexpected unit");
+    return std::max(aValue1, aValue2);
+  }
+
+  result_type
+  MergeClamp(result_type aMin, result_type aCenter, result_type aMax)
+  {
+    return std::max(aMin, std::min(aCenter, aMax));
+  }
 };
 
 /**
@@ -255,8 +318,20 @@ template <class CalcOps>
 static void
 SerializeCalc(const typename CalcOps::input_type& aValue, CalcOps &aOps)
 {
-  aOps.Append("calc(");
   nsCSSUnit unit = CalcOps::GetUnit(aValue);
+  if (unit == eCSSUnit_Calc) {
+    const typename CalcOps::input_array_type *array = aValue.GetArrayValue();
+    MOZ_ASSERT(array->Count() == 1, "unexpected length");
+    nsCSSUnit childUnit = CalcOps::GetUnit(array->Item(0));
+    if (childUnit == eCSSUnit_Calc_Min ||
+        childUnit == eCSSUnit_Calc_Max ||
+        childUnit == eCSSUnit_Calc_Clamp) {
+      SerializeCalcInternal(array->Item(0), aOps);
+      return;
+    }
+  }
+
+  aOps.Append("calc(");
   if (unit == eCSSUnit_Calc) {
     const typename CalcOps::input_array_type *array = aValue.GetArrayValue();
     MOZ_ASSERT(array->Count() == 1, "unexpected length");
@@ -282,6 +357,14 @@ IsCalcMultiplicativeUnit(nsCSSUnit aUnit)
          aUnit == eCSSUnit_Calc_Divided;
 }
 
+static inline bool
+IsCalcMinMaxClampUnit(nsCSSUnit aUnit)
+{
+  return aUnit == eCSSUnit_Calc_Min ||
+         aUnit == eCSSUnit_Calc_Max ||
+         aUnit == eCSSUnit_Calc_Clamp;
+}
+
 // Serialize a non-toplevel value in a calc() tree.  See big comment
 // above.
 template <class CalcOps>
@@ -340,6 +423,29 @@ SerializeCalcInternal(const typename CalcOps::input_type& aValue, CalcOps &aOps)
     if (needParens) {
       aOps.Append(")");
     }
+  } else if (IsCalcMinMaxClampUnit(unit)) {
+    const typename CalcOps::input_array_type *array = aValue.GetArrayValue();
+    MOZ_ASSERT(unit != eCSSUnit_Calc_Clamp || array->Count() == 3,
+               "unexpected length");
+    MOZ_ASSERT(unit == eCSSUnit_Calc_Clamp || array->Count() >= 1,
+               "unexpected length");
+
+    if (unit == eCSSUnit_Calc_Min) {
+      aOps.Append("min(");
+    } else if (unit == eCSSUnit_Calc_Max) {
+      aOps.Append("max(");
+    } else {
+      MOZ_ASSERT(unit == eCSSUnit_Calc_Clamp, "unexpected unit");
+      aOps.Append("clamp(");
+    }
+
+    for (uint32_t i = 0; i < array->Count(); ++i) {
+      if (i != 0) {
+        aOps.Append(", ");
+      }
+      SerializeCalcInternal(array->Item(i), aOps);
+    }
+    aOps.Append(")");
   } else {
     aOps.AppendLeafValue(aValue);
   }

layout/style/nsCSSParser.cpp

@@ -348,6 +348,31 @@ GetCalcLengthTypedArithmeticExponent(const nsCSSValue& aValue,
       return true;
     }
 
+    case eCSSUnit_Calc_Min:
+    case eCSSUnit_Calc_Max:
+    case eCSSUnit_Calc_Clamp: {
+      nsCSSValue::Array* array = aValue.GetArrayValue();
+      MOZ_ASSERT(aValue.GetUnit() != eCSSUnit_Calc_Clamp ||
+                 array->Count() == 3, "unexpected length");
+      MOZ_ASSERT(aValue.GetUnit() == eCSSUnit_Calc_Clamp ||
+                 array->Count() >= 1, "unexpected length");
+
+      int32_t exponent;
+      if (!GetCalcLengthTypedArithmeticExponent(array->Item(0), exponent)) {
+        return false;
+      }
+      for (uint32_t i = 1; i < array->Count(); ++i) {
+        int32_t itemExponent;
+        if (!GetCalcLengthTypedArithmeticExponent(array->Item(i),
+                                                  itemExponent) ||
+            itemExponent != exponent) {
+          return false;
+        }
+      }
+      aExponent = exponent;
+      return true;
+    }
+
     case eCSSUnit_Number:
       aExponent = 0;
       return true;
@@ -430,6 +455,35 @@ NormalizeCalcForVariant(nsCSSValue& aValue,
   return false;
 }
 
+static bool
+MergeCalcFunctionVariantMask(uint32_t& aMergedMask, uint32_t aItemMask)
+{
+  MOZ_ASSERT(aItemMask != 0, "unexpected empty item mask");
+  if (aMergedMask == 0) {
+    aMergedMask = aItemMask;
+    return true;
+  }
+
+  const bool mergedIsNumber = (aMergedMask & VARIANT_NUMBER) != 0;
+  const bool itemIsNumber = (aItemMask & VARIANT_NUMBER) != 0;
+  if (mergedIsNumber || itemIsNumber) {
+    return mergedIsNumber == itemIsNumber;
+  }
+
+  const uint32_t lengthPercentMask = VARIANT_LENGTH | VARIANT_PERCENT;
+  if ((aMergedMask & lengthPercentMask) && (aItemMask & lengthPercentMask)) {
+    aMergedMask = (aMergedMask | aItemMask) & lengthPercentMask;
+    return true;
+  }
+
+  if ((aMergedMask & aItemMask) != 0) {
+    aMergedMask &= aItemMask;
+    return true;
+  }
+
+  return false;
+}
+
 static_assert(css::eAuthorSheetFeatures == 0 &&
               css::eUserSheetFeatures == 1 &&
               css::eAgentSheetFeatures == 2,
@@ -1251,6 +1305,8 @@ protected:
                                          uint32_t& aVariantMask,
                                          bool *aHadFinalWS);
   bool ParseCalcTerm(nsCSSValue& aValue, uint32_t& aVariantMask);
+  bool ParseCalcMinMaxClampFunction(nsCSSValue& aValue,
+                                    uint32_t& aVariantMask);
   bool ParseCalcNumberExpressionValue(float& aValue);
   bool ParseCalcNumberFunction(nsCSSValue& aValue, uint32_t& aVariantMask);
   bool RequireWhitespace();
@@ -13708,7 +13764,8 @@ CSSParserImpl::IsCalcFunctionToken(const nsCSSToken& aToken) const
 {
   return aToken.mType == eCSSToken_Function &&
          (aToken.mIdent.LowerCaseEqualsLiteral("calc") ||
-          aToken.mIdent.LowerCaseEqualsLiteral("-moz-calc"));
+          aToken.mIdent.LowerCaseEqualsLiteral("-moz-calc") ||
+          IsCalcNumberFunctionName(aToken.mIdent));
 }
 
 // Parse one item of the background shorthand property.
@@ -15052,8 +15109,16 @@ CSSParserImpl::ParseCalc(nsCSSValue& aValue, uint32_t aVariantMask,
     RefPtr<nsCSSValue::Array> arr = nsCSSValue::Array::Create(1);
     uint32_t resultVariantMask = aVariantMask;
 
-    if (!ParseCalcAdditiveExpression(arr->Item(0), resultVariantMask))
+    const bool isMinMaxClamp =
+      mToken.mType == eCSSToken_Function &&
+      IsCalcNumberFunctionName(mToken.mIdent);
+    if (isMinMaxClamp) {
+      if (!ParseCalcMinMaxClampFunction(arr->Item(0), resultVariantMask)) {
         break;
+      }
+    } else if (!ParseCalcAdditiveExpression(arr->Item(0), resultVariantMask)) {
+      break;
+    }
 
     if (mCalcAllowsTypedArithmetic) {
       int32_t exponent;
@@ -15074,8 +15139,9 @@ CSSParserImpl::ParseCalc(nsCSSValue& aValue, uint32_t aVariantMask,
       }
     }
 
-    if (!ExpectSymbol(')', true))
+    if (!isMinMaxClamp && !ExpectSymbol(')', true)) {
       break;
+    }
 
     aValue.SetArrayValue(arr, eCSSUnit_Calc);
     if (aResultVariantMask) {
@@ -15285,6 +15351,14 @@ CSSParserImpl::ParseCalcTerm(nsCSSValue& aValue, uint32_t& aVariantMask)
   MOZ_ASSERT(aVariantMask != 0, "unexpected variant mask");
   if (!GetToken(true))
     return false;
+  if (mToken.mType == eCSSToken_Function &&
+      IsCalcNumberFunctionName(mToken.mIdent)) {
+    if (!ParseCalcMinMaxClampFunction(aValue, aVariantMask)) {
+      SkipUntil(')');
+      return false;
+    }
+    return true;
+  }
   // Either an additive expression in parentheses...
   if (mToken.IsSymbol('(') ||
       // Treat nested calc() as plain parenthesis.
@@ -15296,14 +15370,6 @@ CSSParserImpl::ParseCalcTerm(nsCSSValue& aValue, uint32_t& aVariantMask)
     }
     return true;
   }
-  if (mToken.mType == eCSSToken_Function &&
-      IsCalcNumberFunctionName(mToken.mIdent)) {
-    if (!ParseCalcNumberFunction(aValue, aVariantMask)) {
-      SkipUntil(')');
-      return false;
-    }
-    return true;
-  }
   if ((aVariantMask & VARIANT_NUMBER) != 0 &&
       mToken.mType == eCSSToken_Ident) {
     float specialValue;
@@ -15338,6 +15404,63 @@ CSSParserImpl::ParseCalcTerm(nsCSSValue& aValue, uint32_t& aVariantMask)
   return true;
 }
 
+bool
+CSSParserImpl::ParseCalcMinMaxClampFunction(nsCSSValue& aValue,
+                                            uint32_t& aVariantMask)
+{
+  MOZ_ASSERT(mToken.mType == eCSSToken_Function, "expected function token");
+  MOZ_ASSERT(IsCalcNumberFunctionName(mToken.mIdent),
+             "unexpected calc() math function");
+
+  nsCSSUnit unit;
+  if (mToken.mIdent.LowerCaseEqualsLiteral("min")) {
+    unit = eCSSUnit_Calc_Min;
+  } else if (mToken.mIdent.LowerCaseEqualsLiteral("max")) {
+    unit = eCSSUnit_Calc_Max;
+  } else {
+    MOZ_ASSERT(mToken.mIdent.LowerCaseEqualsLiteral("clamp"),
+               "unexpected calc() math function");
+    unit = eCSSUnit_Calc_Clamp;
+  }
+
+  AutoTArray<nsCSSValue, 4> arguments;
+  uint32_t mergedVariantMask = 0;
+
+  for (;;) {
+    nsCSSValue* argument = arguments.AppendElement();
+    uint32_t argumentVariantMask = aVariantMask;
+    if (!ParseCalcAdditiveExpression(*argument, argumentVariantMask) ||
+        !MergeCalcFunctionVariantMask(mergedVariantMask,
+                                      argumentVariantMask)) {
+      return false;
+    }
+
+    if (!ExpectSymbol(',', true)) {
+      break;
+    }
+  }
+
+  const uint32_t argumentCount = arguments.Length();
+  if ((unit == eCSSUnit_Calc_Clamp && argumentCount != 3) ||
+      (unit != eCSSUnit_Calc_Clamp && argumentCount == 0) ||
+      !ExpectSymbol(')', true)) {
+    return false;
+  }
+
+  if (unit != eCSSUnit_Calc_Clamp && argumentCount == 1) {
+    aValue = arguments[0];
+  } else {
+    RefPtr<nsCSSValue::Array> array = nsCSSValue::Array::Create(argumentCount);
+    for (uint32_t i = 0; i < argumentCount; ++i) {
+      array->Item(i) = arguments[i];
+    }
+    aValue.SetArrayValue(array, unit);
+  }
+
+  aVariantMask = mergedVariantMask;
+  return true;
+}
+
 bool
 CSSParserImpl::ParseCalcNumberExpressionValue(float& aValue)
 {

layout/style/nsCSSValue.cpp

@@ -1693,7 +1693,6 @@ nsCSSValue::AppendToString(nsCSSPropertyID aProperty, nsAString& aResult,
     aResult.Append(')');
   }
   else if (IsCalcUnit()) {
-    MOZ_ASSERT(GetUnit() == eCSSUnit_Calc, "unexpected unit");
     if (!AppendNormalizedLengthPercentCalcToString(*this, aProperty, aResult,
                                                    aSerialization)) {
       CSSValueSerializeCalcOps ops(aProperty, aResult, aSerialization);
@@ -2266,6 +2265,9 @@ nsCSSValue::AppendToString(nsCSSPropertyID aProperty, nsAString& aResult,
     case eCSSUnit_Calc_Times_L: break;
     case eCSSUnit_Calc_Times_R: break;
     case eCSSUnit_Calc_Divided: break;
+    case eCSSUnit_Calc_Min:     break;
+    case eCSSUnit_Calc_Max:     break;
+    case eCSSUnit_Calc_Clamp:   break;
     case eCSSUnit_Integer:      break;
     case eCSSUnit_Enumerated:   break;
     case eCSSUnit_EnumColor:             break;
@@ -2398,6 +2400,9 @@ nsCSSValue::SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
     case eCSSUnit_Calc_Times_L:
     case eCSSUnit_Calc_Times_R:
     case eCSSUnit_Calc_Divided:
+    case eCSSUnit_Calc_Min:
+    case eCSSUnit_Calc_Max:
+    case eCSSUnit_Calc_Clamp:
       break;
 
     // URL

layout/style/nsRuleNode.cpp

@@ -798,6 +798,16 @@ CalcLengthTowardZero(const nsCSSValue& aValue,
                         AppUnitRounding::TowardZero);
 }
 
+already_AddRefed<nsStyleCoord::CalcNode>
+nsRuleNode::ComputedCalc::ToCalcNode() const
+{
+  if (mNode) {
+    RefPtr<nsStyleCoord::CalcNode> node = mNode;
+    return node.forget();
+  }
+  return nsStyleCoord::CalcNode::CreateLeaf(mLength, mPercent, mHasPercent);
+}
+
 /* static */ nscoord
 nsRuleNode::CalcLengthWithInitialFont(nsPresContext* aPresContext,
                                       const nsCSSValue& aValue)
@@ -830,27 +840,42 @@ struct LengthPercentPairCalcOps : public css::NumbersAlreadyNormalizedOps
   {
     if (aValue.GetUnit() == eCSSUnit_Percent) {
       mHasPercent = true;
-      return result_type(0, aValue.GetPercentValue());
+      return result_type(0, aValue.GetPercentValue(), true);
     }
     return result_type(CalcLength(aValue, mContext, mPresContext,
                                   mConditions),
-                       0.0f);
+                       0.0f, false);
   }
 
   result_type
   MergeAdditive(nsCSSUnit aCalcFunction,
                 result_type aValue1, result_type aValue2)
   {
+    if (aValue1.HasNode() || aValue2.HasNode()) {
+      RefPtr<nsStyleCoord::CalcNode> node =
+        nsStyleCoord::CalcNode::Create(
+          aCalcFunction == eCSSUnit_Calc_Plus
+            ? nsStyleCoord::CalcNode::Type::Add
+            : nsStyleCoord::CalcNode::Type::Subtract);
+      node->mChildren.AppendElement(aValue1.ToCalcNode());
+      node->mChildren.AppendElement(aValue2.ToCalcNode());
+      node->mHasPercent = node->HasPercent();
+      mHasPercent = mHasPercent || node->mHasPercent;
+      return result_type(node.forget());
+    }
+
     if (aCalcFunction == eCSSUnit_Calc_Plus) {
       return result_type(NSCoordSaturatingAdd(aValue1.mLength,
                                               aValue2.mLength),
-                         aValue1.mPercent + aValue2.mPercent);
+                         aValue1.mPercent + aValue2.mPercent,
+                         aValue1.mHasPercent || aValue2.mHasPercent);
     }
     MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Minus,
                "min() and max() are not allowed in calc() on transform");
     return result_type(NSCoordSaturatingSubtract(aValue1.mLength,
                                                  aValue2.mLength, 0),
-                       aValue1.mPercent - aValue2.mPercent);
+                       aValue1.mPercent - aValue2.mPercent,
+                       aValue1.mHasPercent || aValue2.mHasPercent);
   }
 
   result_type
@@ -859,8 +884,19 @@ struct LengthPercentPairCalcOps : public css::NumbersAlreadyNormalizedOps
   {
     MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Times_L,
                "unexpected unit");
+    if (aValue2.HasNode()) {
+      RefPtr<nsStyleCoord::CalcNode> node =
+        nsStyleCoord::CalcNode::Create(nsStyleCoord::CalcNode::Type::Multiply);
+      node->mChildren.AppendElement(aValue2.ToCalcNode());
+      node->mNumber = aValue1;
+      node->mHasPercent = node->HasPercent();
+      mHasPercent = mHasPercent || node->mHasPercent;
+      return result_type(node.forget());
+    }
+
     return result_type(NSCoordSaturatingMultiply(aValue2.mLength, aValue1),
-                       aValue1 * aValue2.mPercent);
+                       aValue1 * aValue2.mPercent,
+                       aValue2.mHasPercent);
   }
 
   result_type
@@ -871,10 +907,89 @@ struct LengthPercentPairCalcOps : public css::NumbersAlreadyNormalizedOps
                aCalcFunction == eCSSUnit_Calc_Divided,
                "unexpected unit");
     if (aCalcFunction == eCSSUnit_Calc_Divided) {
+      if (aValue1.HasNode()) {
+        RefPtr<nsStyleCoord::CalcNode> node =
+          nsStyleCoord::CalcNode::Create(nsStyleCoord::CalcNode::Type::Divide);
+        node->mChildren.AppendElement(aValue1.ToCalcNode());
+        node->mNumber = aValue2;
+        node->mHasPercent = node->HasPercent();
+        mHasPercent = mHasPercent || node->mHasPercent;
+        return result_type(node.forget());
+      }
       aValue2 = 1.0f / aValue2;
+    } else if (aValue1.HasNode()) {
+      RefPtr<nsStyleCoord::CalcNode> node =
+        nsStyleCoord::CalcNode::Create(nsStyleCoord::CalcNode::Type::Multiply);
+      node->mChildren.AppendElement(aValue1.ToCalcNode());
+      node->mNumber = aValue2;
+      node->mHasPercent = node->HasPercent();
+      mHasPercent = mHasPercent || node->mHasPercent;
+      return result_type(node.forget());
     }
     return result_type(NSCoordSaturatingMultiply(aValue1.mLength, aValue2),
-                       aValue1.mPercent * aValue2);
+                       aValue1.mPercent * aValue2,
+                       aValue1.mHasPercent);
+  }
+
+  result_type
+  MergeMinMax(nsCSSUnit aCalcFunction,
+              result_type aValue1, result_type aValue2)
+  {
+    const bool hasNode = aValue1.HasNode() || aValue2.HasNode();
+    const bool hasPercent = aValue1.mHasPercent || aValue2.mHasPercent;
+    if (!hasNode && !hasPercent) {
+      if (aCalcFunction == eCSSUnit_Calc_Min) {
+        return result_type(std::min(aValue1.mLength, aValue2.mLength),
+                           0.0f, false);
+      }
+      MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Max, "unexpected unit");
+      return result_type(std::max(aValue1.mLength, aValue2.mLength),
+                         0.0f, false);
+    }
+
+    RefPtr<nsStyleCoord::CalcNode> node =
+      nsStyleCoord::CalcNode::Create(
+        aCalcFunction == eCSSUnit_Calc_Min
+          ? nsStyleCoord::CalcNode::Type::Min
+          : nsStyleCoord::CalcNode::Type::Max);
+    if (aValue1.HasNode() &&
+        aValue1.mNode->mType == node->mType) {
+      node->mChildren.AppendElements(aValue1.mNode->mChildren);
+    } else {
+      node->mChildren.AppendElement(aValue1.ToCalcNode());
+    }
+    if (aValue2.HasNode() &&
+        aValue2.mNode->mType == node->mType) {
+      node->mChildren.AppendElements(aValue2.mNode->mChildren);
+    } else {
+      node->mChildren.AppendElement(aValue2.ToCalcNode());
+    }
+    node->mHasPercent = node->HasPercent();
+    mHasPercent = mHasPercent || node->mHasPercent;
+    return result_type(node.forget());
+  }
+
+  result_type
+  MergeClamp(result_type aMin, result_type aCenter, result_type aMax)
+  {
+    const bool hasNode = aMin.HasNode() || aCenter.HasNode() || aMax.HasNode();
+    const bool hasPercent = aMin.mHasPercent ||
+                            aCenter.mHasPercent ||
+                            aMax.mHasPercent;
+    if (!hasNode && !hasPercent) {
+      return result_type(std::max(aMin.mLength,
+                                  std::min(aCenter.mLength, aMax.mLength)),
+                         0.0f, false);
+    }
+
+    RefPtr<nsStyleCoord::CalcNode> node =
+      nsStyleCoord::CalcNode::Create(nsStyleCoord::CalcNode::Type::Clamp);
+    node->mChildren.AppendElement(aMin.ToCalcNode());
+    node->mChildren.AppendElement(aCenter.ToCalcNode());
+    node->mChildren.AppendElement(aMax.ToCalcNode());
+    node->mHasPercent = node->HasPercent();
+    mHasPercent = mHasPercent || node->mHasPercent;
+    return result_type(node.forget());
   }
 
 };
@@ -892,7 +1007,8 @@ SpecifiedCalcToComputedCalc(const nsCSSValue& aValue, nsStyleCoord& aCoord,
 
   calcObj->mLength = vals.mLength;
   calcObj->mPercent = vals.mPercent;
-  calcObj->mHasPercent = ops.mHasPercent;
+  calcObj->mHasPercent = vals.mHasPercent || ops.mHasPercent;
+  calcObj->mNode = vals.mNode;
 
   aCoord.SetCalcValue(calcObj);
 }
@@ -915,8 +1031,7 @@ nsRuleNode::ComputeComputedCalc(const nsStyleCoord& aValue,
                                 nscoord aPercentageBasis)
 {
   nsStyleCoord::Calc* calc = aValue.GetCalcValue();
-  return calc->mLength +
+  return calc->Resolve(aPercentageBasis);
-         NSToCoordFloorClamped(aPercentageBasis * calc->mPercent);
 }
 
 /* static */ nscoord
@@ -5110,6 +5225,34 @@ struct LengthNumberCalcOps : public css::NumbersAlreadyNormalizedOps
     return result;
   }
 
+  result_type
+  MergeMinMax(nsCSSUnit aCalcFunction,
+              result_type aValue1, result_type aValue2)
+  {
+    MOZ_ASSERT(aValue1.mIsNumber == aValue2.mIsNumber);
+    LengthNumberCalcObj result;
+    result.mIsNumber = aValue1.mIsNumber;
+    if (aCalcFunction == eCSSUnit_Calc_Min) {
+      result.mValue = std::min(aValue1.mValue, aValue2.mValue);
+      return result;
+    }
+    MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Max, "unexpected unit");
+    result.mValue = std::max(aValue1.mValue, aValue2.mValue);
+    return result;
+  }
+
+  result_type
+  MergeClamp(result_type aMin, result_type aCenter, result_type aMax)
+  {
+    MOZ_ASSERT(aMin.mIsNumber == aCenter.mIsNumber &&
+               aCenter.mIsNumber == aMax.mIsNumber);
+    LengthNumberCalcObj result;
+    result.mIsNumber = aCenter.mIsNumber;
+    result.mValue = std::max(aMin.mValue,
+                             std::min(aCenter.mValue, aMax.mValue));
+    return result;
+  }
+
   result_type ComputeLeafValue(const nsCSSValue& aValue)
   {
     LengthNumberCalcObj result;
@@ -5200,6 +5343,38 @@ struct LengthPercentNumberCalcOps : public css::NumbersAlreadyNormalizedOps
     return result;
   }
 
+  result_type
+  MergeMinMax(nsCSSUnit aCalcFunction,
+              result_type aValue1, result_type aValue2)
+  {
+    MOZ_ASSERT(aValue1.mIsNumber == aValue2.mIsNumber);
+    result_type result;
+    result.mIsNumber = aValue1.mIsNumber;
+    if (aCalcFunction == eCSSUnit_Calc_Min) {
+      result.mLength = std::min(aValue1.mLength, aValue2.mLength);
+      result.mPercent = std::min(aValue1.mPercent, aValue2.mPercent);
+    } else {
+      MOZ_ASSERT(aCalcFunction == eCSSUnit_Calc_Max, "unexpected unit");
+      result.mLength = std::max(aValue1.mLength, aValue2.mLength);
+      result.mPercent = std::max(aValue1.mPercent, aValue2.mPercent);
+    }
+    return result;
+  }
+
+  result_type
+  MergeClamp(result_type aMin, result_type aCenter, result_type aMax)
+  {
+    MOZ_ASSERT(aMin.mIsNumber == aCenter.mIsNumber &&
+               aCenter.mIsNumber == aMax.mIsNumber);
+    result_type result;
+    result.mIsNumber = aCenter.mIsNumber;
+    result.mLength = std::max(aMin.mLength,
+                              std::min(aCenter.mLength, aMax.mLength));
+    result.mPercent = std::max(aMin.mPercent,
+                               std::min(aCenter.mPercent, aMax.mPercent));
+    return result;
+  }
+
   result_type
   ComputeLeafValue(const nsCSSValue& aValue)
   {