fix radius expression

Author: dgthanhan

StencilBuilder/Definition.xml

@@ -52,6 +52,12 @@
                     info.valueLiteral = this.getProperty(propName + "Expression").value;
                     info.realValueLiteral = info.valueLiteral;
 
+                    if (behaviorNames) for (var behaviorName of behaviorNames.split(",")) contribution.addBehavior(targetElementName, behaviorName, [expressionConverter ? expressionConverter(info.valueLiteral) : info.valueLiteral]);
+                    return info;
+                } else if (mode.match(/^\$.+/)) {
+                    info.valueLiteral = mode;
+                    info.realValueLiteral = info.valueLiteral;
+
                     if (behaviorNames) for (var behaviorName of behaviorNames.split(",")) contribution.addBehavior(targetElementName, behaviorName, [expressionConverter ? expressionConverter(info.valueLiteral) : info.valueLiteral]);
                     return info;
                 } else {
@@ -770,7 +776,7 @@
                     contribution = parentAction.implFunction.call(this);
 
                     var converter = contribution._boundExpressionLiteral ? function (e) {
-                        return "(" + e + ").x - (" + contribution._boundExpressionLiteral + ").x";
+                        return "Math.max(0, (" + e + ").x - (" + contribution._boundExpressionLiteral + ").x)";
                     } : null;
 
                     var meta = {minX: "0", lockY: "true"};