Add API to compute length, percentage or calc() style coords. (Bug 363249) r=bzbarsky

layout/style/nsRuleNode.cpp

@@ -559,6 +559,22 @@ nsRuleNode::ComputeComputedCalc(const nsStyleCoord& aValue,
   return css::ComputeCalc(aValue, ops);
 }
 
+/* static */ nscoord
+nsRuleNode::ComputeCoordPercentCalc(const nsStyleCoord& aCoord,
+                                    nscoord aPercentageBasis)
+{
+  switch (aCoord.GetUnit()) {
+    case eStyleUnit_Coord:
+      return aCoord.GetCoordValue();
+    case eStyleUnit_Percent:
+      return NSCoordSaturatingMultiply(aPercentageBasis,
+                                       aCoord.GetPercentValue());
+    default:
+      NS_ABORT_IF_FALSE(aCoord.IsCalcUnit(), "unexpected unit");
+      return nsRuleNode::ComputeComputedCalc(aCoord, aPercentageBasis);
+  }
+}
+
 #define SETCOORD_NORMAL                 0x01   // N
 #define SETCOORD_AUTO                   0x02   // A
 #define SETCOORD_INHERIT                0x04   // H

layout/style/nsRuleNode.h

@@ -62,6 +62,8 @@ struct nsRuleDataFont;
 class nsCSSValue;
 struct nsCSSRect;
 
+class nsStyleCoord;
+
 struct nsInheritedStyleData
 {
 
@@ -762,6 +764,11 @@ public:
   static nscoord ComputeComputedCalc(const nsStyleCoord& aCoord,
                                      nscoord aPercentageBasis);
 
+  // Compute the value of an nsStyleCoord that is either a coord, a
+  // percent, or a calc expression.
+  static nscoord ComputeCoordPercentCalc(const nsStyleCoord& aCoord,
+                                         nscoord aPercentageBasis);
+
   // Return whether the rule tree for which this node is the root has
   // cached data such that we need to do dynamic change handling for
   // changes that change the results of media queries or require