JSON: Added the ability to limit the number of decimal places when serialising floating point numbers

BREAKING-CHANGES.txt

@@ -1,6 +1,34 @@
 JUCE breaking changes
 =====================
 
+Develop Branch
+=============
+
+Change
+------
+The writeAsJSON virtual method of the DynamicObject class requires an
+additional parameter, maximumDecimalPlaces, to specify the maximum precision of
+floating point numbers.
+
+Possible Issues
+---------------
+Classes which inherit from DynamicObject and override this method will need to
+update their method signature.
+
+Workaround
+----------
+Your custom DynamicObject class can choose to ignore the additional parameter
+if you don't wish to support this behaviour.
+
+Rationale
+---------
+When serialising the results of calculations to JSON the rounding of floating
+point numbers can result in numbers with 17 significant figures where only a
+few are required. This change to DynamicObject is required to support
+truncating those numbers.
+
+
+
 Version 5.1.0
 =============
 

modules/juce_core/containers/juce_DynamicObject.cpp

@@ -91,7 +91,7 @@ DynamicObject::Ptr DynamicObject::clone()
     return d;
 }
 
-void DynamicObject::writeAsJSON (OutputStream& out, const int indentLevel, const bool allOnOneLine)
+void DynamicObject::writeAsJSON (OutputStream& out, const int indentLevel, const bool allOnOneLine, int maximumDecimalPlaces)
 {
     out << '{';
     if (! allOnOneLine)
@@ -107,7 +107,7 @@ void DynamicObject::writeAsJSON (OutputStream& out, const int indentLevel, const
         out << '"';
         JSONFormatter::writeString (out, properties.getName (i));
         out << "\": ";
-        JSONFormatter::write (out, properties.getValueAt (i), indentLevel + JSONFormatter::indentSize, allOnOneLine);
+        JSONFormatter::write (out, properties.getValueAt (i), indentLevel + JSONFormatter::indentSize, allOnOneLine, maximumDecimalPlaces);
 
         if (i < numValues - 1)
         {

modules/juce_core/containers/juce_DynamicObject.h

@@ -113,14 +113,14 @@ public:
         never need to call it directly, but it's virtual so that custom object types
         can stringify themselves appropriately.
     */
-    virtual void writeAsJSON (OutputStream&, int indentLevel, bool allOnOneLine);
+    virtual void writeAsJSON (OutputStream&, int indentLevel, bool allOnOneLine, int maximumDecimalPlaces);
 
 private:
     //==============================================================================
     NamedValueSet properties;
 
    #if JUCE_CATCH_DEPRECATED_CODE_MISUSE
-    // These methods have been deprecated - use var::invoke instead
+    // This method has been deprecated - use var::invoke instead
     virtual void invokeMethod (const Identifier&, const var*, int) {}
    #endif
 

modules/juce_core/javascript/juce_JSON.cpp

@@ -323,7 +323,8 @@ class JSONFormatter
 {
 public:
     static void write (OutputStream& out, const var& v,
-                       const int indentLevel, const bool allOnOneLine)
+                       const int indentLevel, const bool allOnOneLine,
+                       int maximumDecimalPlaces)
     {
         if (v.isString())
         {
@@ -343,14 +344,18 @@ public:
         {
             out << (static_cast<bool> (v) ? "true" : "false");
         }
+        else if (v.isDouble())
+        {
+            out << String (static_cast<double> (v), maximumDecimalPlaces);
+        }
         else if (v.isArray())
         {
-            writeArray (out, *v.getArray(), indentLevel, allOnOneLine);
+            writeArray (out, *v.getArray(), indentLevel, allOnOneLine, maximumDecimalPlaces);
         }
         else if (v.isObject())
         {
             if (DynamicObject* object = v.getDynamicObject())
-                object->writeAsJSON (out, indentLevel, allOnOneLine);
+                object->writeAsJSON (out, indentLevel, allOnOneLine, maximumDecimalPlaces);
             else
                 jassertfalse; // Only DynamicObjects can be converted to JSON!
         }
@@ -420,7 +425,8 @@ public:
     }
 
     static void writeArray (OutputStream& out, const Array<var>& array,
-                            const int indentLevel, const bool allOnOneLine)
+                            const int indentLevel, const bool allOnOneLine,
+                            int maximumDecimalPlaces)
     {
         out << '[';
 
@@ -434,7 +440,7 @@ public:
                 if (! allOnOneLine)
                     writeSpaces (out, indentLevel + indentSize);
 
-                write (out, array.getReference(i), indentLevel + indentSize, allOnOneLine);
+                write (out, array.getReference(i), indentLevel + indentSize, allOnOneLine, maximumDecimalPlaces);
 
                 if (i < array.size() - 1)
                 {
@@ -493,16 +499,16 @@ Result JSON::parse (const String& text, var& result)
     return JSONParser::parseObjectOrArray (text.getCharPointer(), result);
 }
 
-String JSON::toString (const var& data, const bool allOnOneLine)
+String JSON::toString (const var& data, const bool allOnOneLine, int maximumDecimalPlaces)
 {
     MemoryOutputStream mo (1024);
-    JSONFormatter::write (mo, data, 0, allOnOneLine);
+    JSONFormatter::write (mo, data, 0, allOnOneLine, maximumDecimalPlaces);
     return mo.toUTF8();
 }
 
-void JSON::writeToStream (OutputStream& output, const var& data, const bool allOnOneLine)
+void JSON::writeToStream (OutputStream& output, const var& data, const bool allOnOneLine, int maximumDecimalPlaces)
 {
-    JSONFormatter::write (output, data, 0, allOnOneLine);
+    JSONFormatter::write (output, data, 0, allOnOneLine, maximumDecimalPlaces);
 }
 
 String JSON::escapeString (StringRef s)

modules/juce_core/javascript/juce_JSON.h

@@ -90,10 +90,12 @@ public:
     /** Returns a string which contains a JSON-formatted representation of the var object.
         If allOnOneLine is true, the result will be compacted into a single line of text
         with no carriage-returns. If false, it will be laid-out in a more human-readable format.
+        The maximumDecimalPlaces parameter determines the precision of floating point numbers.
         @see writeToStream
     */
     static String toString (const var& objectToFormat,
-                            bool allOnOneLine = false);
+                            bool allOnOneLine = false,
+                            int maximumDecimalPlaces = 20);
 
     /** Parses a string that was created with the toString() method.
         This is slightly different to the parse() methods because they will reject primitive
@@ -105,11 +107,13 @@ public:
     /** Writes a JSON-formatted representation of the var object to the given stream.
         If allOnOneLine is true, the result will be compacted into a single line of text
         with no carriage-returns. If false, it will be laid-out in a more human-readable format.
+        The maximumDecimalPlaces parameter determines the precision of floating point numbers.
         @see toString
     */
     static void writeToStream (OutputStream& output,
                                const var& objectToFormat,
-                               bool allOnOneLine = false);
+                               bool allOnOneLine = false,
+                               int maximumDecimalPlaces = 20);
 
     /** Returns a version of a string with any extended characters escaped. */
     static String escapeString (StringRef);

modules/juce_core/javascript/juce_Javascript.cpp

@@ -827,7 +827,7 @@ struct JavascriptEngine::RootObject   : public DynamicObject
 
         DynamicObject::Ptr clone() override    { return new FunctionObject (*this); }
 
-        void writeAsJSON (OutputStream& out, int /*indentLevel*/, bool /*allOnOneLine*/) override
+        void writeAsJSON (OutputStream& out, int /*indentLevel*/, bool /*allOnOneLine*/, int /*maximumDecimalPlaces*/) override
         {
             out << "function " << functionCode;
         }