Own backend for SVG files

Hi All,
I'm writing my own backend to graphic interface for SVG files.

First I have reimplemented all QPaintEngine virtual functions writing my own PaintEngine.
Then I write my own PaintDevice, reimplementing the QPaintDevice::paintEngine() function of QPaintDevice.

Finally I pass my own PaintDevice to the QPainter that is used from QSvgRenderer.

Now I see that only the functions drawPixMap and drawImage (of my own PaintEngine) are called although there are many others functions like drawLines, drawPolygon, drawPath... in QPaintEngine and I load a simple image that only have some lines.

Why these functions aren't called? I need them because for my own backend I need vectorial information while drawPixMap and drawImage give me only raster information.

Should I initialize QPaintEngine or QSvgRender or QPainter... with some particular parameter?
Has someone worked with SVG files?

Thanks