Render QML scene problem

[oosavu]

Hello All!
My previous question was not answered, and I'll try to explain more clearly, and sory for my bad english.

I develop application for embeded system (AM3517 processor based, EGLFS platform).

I have very big QML scene (several dozen of Rectangle{} and Text{} items), and I need display little xy-plot in QML scene. This xy-plot should be updated very often (50 Hz). The trouble is that a QQuickWindow::update() function call is hard CPU-intensive. As I understand it, time of this function depends on how many nodes in scene graph.
I tried to use rendering to FBO (http://qt-project.org/doc/qt-5.1/qtquick/scenegraph-textureinsgnode.html), but this example use full update of scene (call m_window->update(); in TextureNode class). For simple QML scene is not significantly, but for my case is important.
I tired to use Canvas{} element, but i need call Canvas::requestPaint() function for every frame, and this leads to call update() function too.

Is there a way to update only a small area of ​​the screen, without an analysis of the entire scene graph?
Is there a way to make the scene graph renderer does not run all over the scene graph by drawing a single pixel?
maybe there is a workaround to update the small area in QML scene?

My Qt version is 5.0.

[sierdzio]

This is best asked on interest "mailing list":http://lists.qt-project.org/mailman/listinfo/interest. Still no guarantee you'll get an answer, but it's a bit more probable. As an absolute last resort, use development ML.