Cannot disable QGraphicsSimpleText antialiasing with Qt 5.x

I'm trying to display a grayscale picture, on which areas of interest are shown with superimposed reticle-like objects and a small text using the QGraphic View Framework.
I had problem on some hardware with the OpenGL layer, therefore my goal is to let the CPU do the rendering. I added an option to disable antialiasing on displayed view, triggered by a right-click on the picture. The slot which toggles the antialiasing is implemented as:

void PictureDisplay::toggleSmoothing()
{
    QPainter::RenderHints hints( renderHints() );
    hints ^= QPainter::Antialiasing;
    hints ^= QPainter::TextAntialiasing;
    hints ^= QPainter::SmoothPixmapTransform;
    hints ^= QPainter::HighQualityAntialiasing;
    setRenderHints( hints );
    QFont font( "Arial", 18 );
    if ( ( hints & QPainter::HighQualityAntialiasing ) != 0 )
    {
        font.setStyleStrategy( QFont::PreferAntialias );
        foreach ( QGraphicsSimpleTextItem* item, OverlaidTexts )
        {
            item->setFont( font );
        }
        PixmapItem->setTransformationMode( Qt::SmoothTransformation );
    }
    else
    {
        font.setStyleStrategy( QFont::NoAntialias );
        foreach ( QGraphicsSimpleTextItem* item, OverlaidTexts )
        {
            item->setFont( font );
        }
        PixmapItem->setTransformationMode( Qt::FastTransformation );
    }
}

I've tested this code with Qt 5.6.0 64bits on Windows 8.1 using MSVC 2013, Qt 5.4.2 64bits on Mageia 5 using both gcc 4.9 and clang 3.5, Qt 4.8.6 64bits on Mageia 5 using gcc 4.9.
Now, here's the catch:

• the Windows Qt 5.6 version does not disable text antialiasing, unless I use the OpenGL viewport;
• the Linux Qt 5.4 version does not disable text antialiasing (and I have no OpenGL output, i.e. blank widget, but never mind);
• the Linux Qt 4.8 does disable text antialiasing (and I have no OpenGL output, i.e. blank widget, but never mind).

In all cases, the displayed picture and the reticle-like shape respond correctly to the antialiasing toggling.