Improve default focus handling of QmlView

With default configuration, input items do not get focus / do not work within a QmlView.

Say you create a minimal qml example:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    QDeclarativeView *view = new QDeclarativeView;
    view->setSource(QUrl("test.qml"));
    setCentralWidget(view);
}

With test.qml being defined as:

import Qt 4.6
 TextInput{
  width: 200
  height: 200
}

If you launch this, you can click on the Input, and get a blinking cursor, but you can't type. For this you have to change the focusPolicy:

view->setFocusPolicy(Qt::ClickFocus);

This is because QmlView calls

viewport()->setFocusPolicy(Qt::NoFocus)

which doesn't seem right. Also the qml viewer does this:

"canvas->setFocus();"

which can probably be better achieved by setFocusPolicy(Qt::StrongFocus).

(Sometimes you also have to explicitly activate the scene afterwards, e.g. following line is also needed in Bauhaus):

QApplication::sendEvent(myQmlView->scene(), new QEvent(QEvent::WindowActivate));