Use the new memory cost reporting API in QtScript Custom Class example

Also describe its purpose in the example doc.

3 files changed, 30 insertions, 2 deletions

diff --git a/doc/src/examples/qtscriptcustomclass.qdoc b/doc/src/examples/qtscriptcustomclass.qdoc
index f825ad9..028c7a6 100644
--- a/doc/src/examples/qtscriptcustomclass.qdoc
+++ b/doc/src/examples/qtscriptcustomclass.qdoc
@@ -120,6 +120,8 @@
     this ByteArrayClass object, so that the constructor, when it is invoked, can extract the
     pointer and use it to create a new \c{ByteArray} object.
 
+    \snippet examples/script/customclass/bytearrayclass.cpp 10
+
     \snippet examples/script/customclass/bytearrayclass.cpp 1
 
     The newInstance() function isn't part of the QScriptClass API; its purpose is to offer
@@ -128,6 +130,11 @@
     QScriptEngine::newObject() will call the prototype() function of our class, ensuring that
     the prototype of the new object will be the standard \c{ByteArray} prototype.
 
+    QScriptEngine::reportAdditionalMemoryCost() is called to inform the script engine of the
+    memory occupied by the QByteArray. This gives the garbage collector a hint that it should
+    perhaps trigger more frequently, possibly freeing up memory associated with large ByteArray
+    objects that are no longer in use.
+
     \snippet examples/script/customclass/bytearrayclass.cpp 2
 
     construct() is the native function that will act as a constructor for \c{ByteArray}
@@ -159,6 +166,12 @@
     array index that was calculated in the queryProperty() function, enlarge the array if necessary,
     and write the given value to the array.
 
+    \snippet examples/script/customclass/bytearrayclass.cpp 9
+
+    The resize() function is a helper function that resizes the QByteArray to a new size, and,
+    if the new size is greater than the old, reports the additional memory cost to the script
+    engine.
+
     \snippet examples/script/customclass/bytearrayclass.cpp 6
 
     The propertyFlags() reimplementation specifies that the \c{length} property can't be deleted,
diff --git a/examples/script/customclass/bytearrayclass.cpp b/examples/script/customclass/bytearrayclass.cpp
index 1dbf2d4..239b4b4 100644
--- a/examples/script/customclass/bytearrayclass.cpp
+++ b/examples/script/customclass/bytearrayclass.cpp
@@ -148,13 +148,13 @@ void ByteArrayClass::setProperty(QScriptValue &object,
     if (!ba)
         return;
     if (name == length) {
-        ba->resize(value.toInt32());
+        resize(*ba, value.toInt32());
     } else {
         qint32 pos = id;
         if (pos < 0)
             return;
         if (ba->size() <= pos)
-            ba->resize(pos + 1);
+            resize(*ba, pos + 1);
         (*ba)[pos] = char(value.toInt32());
     }
 }
@@ -194,10 +194,13 @@ QScriptValue ByteArrayClass::constructor()
     return ctor;
 }
 
+//! [10]
 QScriptValue ByteArrayClass::newInstance(int size)
 {
+    engine()->reportAdditionalMemoryCost(size);
     return newInstance(QByteArray(size, /*ch=*/0));
 }
+//! [10]
 
 //! [1]
 QScriptValue ByteArrayClass::newInstance(const QByteArray &ba)
@@ -235,6 +238,16 @@ void ByteArrayClass::fromScriptValue(const QScriptValue &obj, QByteArray &ba)
     ba = qvariant_cast<QByteArray>(obj.data().toVariant());
 }
 
+//! [9]
+void ByteArrayClass::resize(QByteArray &ba, int newSize)
+{
+    int oldSize = ba.size();
+    ba.resize(newSize);
+    if (newSize > oldSize)
+        engine()->reportAdditionalMemoryCost(newSize - oldSize);
+}
+//! [9]
+
 
 
 ByteArrayClassPropertyIterator::ByteArrayClassPropertyIterator(const QScriptValue &object)
diff --git a/examples/script/customclass/bytearrayclass.h b/examples/script/customclass/bytearrayclass.h
index f185754..3f7ce22 100644
--- a/examples/script/customclass/bytearrayclass.h
+++ b/examples/script/customclass/bytearrayclass.h
@@ -82,6 +82,8 @@ private:
     static QScriptValue toScriptValue(QScriptEngine *eng, const QByteArray &ba);
     static void fromScriptValue(const QScriptValue &obj, QByteArray &ba);
 
+    void resize(QByteArray &ba, int newSize);
+
     QScriptString length;
     QScriptValue proto;
     QScriptValue ctor;