QtQuick Leak on setSource or API misuse by me?

altera_2011

I'm running into a leak in Qt-Quick (4.7.4 and 4.8.0) when setting a new source using QDeclarativeView->setSource in response to a QML MouseArea click. I've been able to reproduce this with a very minimal application.

mainwindow.h
@#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui/QMainWindow>
#include <QtDeclarative/QtDeclarative>

class MainWindow : public QMainWindow
{
Q_OBJECT
QDeclarativeView * m_View;
bool m_Toggle;
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void changeView( );

private slots:
void setView( QString file );
void toggleView();
};

#endif // MAINWINDOW_H@

mainwindow.cpp
@#include "mainwindow.h"
#include <QTimer>

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent),m_Toggle(true)
{
m_View = new QDeclarativeView(this);
m_View->setSource( QUrl::fromLocalFile("dlg1.qml"));
m_View->rootContext()->setContextProperty("mainWindow", this);

setCentralWidget(m_View);

// automated switching of dialog...
// starting this timer does NOT leak!!!
QTimer * t = new QTimer(this);
t->setInterval(50);
connect(t, SIGNAL(timeout()), this, SLOT(toggleView()));
// t->start();

}

MainWindow::~MainWindow()
{

}

void MainWindow::changeView()
{
// leaks!
QMetaObject::invokeMethod(this, "toggleView", Qt::QueuedConnection);

// leaks as well!
//QTimer::singleShot(1, this, SLOT(toggleView()));

}

void MainWindow::setView(QString file)
{
m_View->setSource( QUrl::fromLocalFile(file));
}

void MainWindow::toggleView()
{
m_Toggle = !m_Toggle;
if ( m_Toggle )
{
setView("dlg1.qml");
}
else
{
setView("dlg2.qml");
}
}@

dlg1.qml (and dlg2.qml with tiny change in text)
@import QtQuick 1.0

Rectangle {
width: 480
height: 272

MouseArea {
    anchors.fill: parent;
    onClicked: {
        mainWindow.changeView();
    }
}

Text {
    anchors.centerIn: parent;
    text: "dialog 1\nclick me"
}

}
@

So every time you click on the screen the app will switch to the other screen. Clicking repeatedly on the screen and looking at the memory use i can see the app memory use increasing. Now for the interesting bit. If I use the QTimer to do the switching I get no leak. But if I start a singleshot timer in response to the mouse click I do get a leak. Each click leaks about 5-10kB, which isn't much but in our full application it leaks about 1MB on each QML change, which on a mobile device will quickly run out of memory. I've tried deleting the view hoping it would release the memory, it did not.

So before I post a bug on this I just want to make sure I'm not using the API incorrectly to display a different QML page.

altera_2011

I tried using a "QML loader":http://doc.qt.nokia.com/4.7-snapshot/qml-loader.html instead of calling setSource from C++ but that also leaks.