Add QJSValue::isCallable() function

This replaces the isFunction() function. isFunction() will be
removed. It's possible that objects are callable even if they aren't
Function instances. Also, "isCallable" is consistent with call().

Task-number: QTBUG-23604
Change-Id: I42e0ab2ad9dc84e7793199254bbd89d5c9466e6a
Reviewed-by: Simon Hausmann <simon.hausmann@nokia.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>

src/declarative/qml/v8/qjsvalue.cpp

@@ -71,7 +71,7 @@
   Object values have an internal \c{prototype} property, which can be
   accessed with prototype() and setPrototype().
 
-  Function objects (objects for which isFunction() returns true) can
+  Function objects (objects for which isCallable()) returns true) can
   be invoked by calling call(). Constructor functions can be used to
   construct new objects by calling construct().
 
@@ -461,11 +461,23 @@ bool QJSValue::isObject() const
 }
 
 /*!
-  Returns true if this QJSValue is a function; otherwise returns
-  false.
+  Returns true if this QJSValue can be called a function, otherwise
+  returns false.
 
   \sa call()
 */
+bool QJSValue::isCallable() const
+{
+    Q_D(const QJSValue);
+    QScriptIsolate api(d->engine());
+    return d->isCallable();
+}
+
+/*!
+  \obsolete
+
+  Use isCallable() instead.
+*/
 bool QJSValue::isFunction() const
 {
     Q_D(const QJSValue);

src/declarative/qml/v8/qjsvalue.h

@@ -140,6 +140,7 @@ class Q_DECLARATIVE_EXPORT QJSValue
 
     QJSValue::PropertyFlags propertyFlags(const QString &name) const;
 
+    bool isCallable() const;
     QJSValue call(const QJSValue &thisObject = QJSValue(),
                       const QJSValueList &args = QJSValueList());
     QJSValue construct(const QJSValueList &args = QJSValueList());