How does Qt4.8(or the Qt 5) do the painting work?
It is probably as same as “ How my program code transition to the GUI on screen device via various Qt5 painting system?”  

Since Qt support various kinds of platforms,my questions only base on Linux and Embedded Linux(because both are opensource os and are different in painting :-) )。

My question focus on these topics:

1, Are QWidget ，QGraphicsItem，Rectangle(in QML) different in the painting system?And what is it ?

2, Which one don't use QPaint（QPaintEngine） class ?

3,How many paint engines implemented in Qt4.8(or Qt5)?For example, QRasterPaintEngine.

4,If the platform is Linux(with X11 supported),will Qt use X11 API do the painting?Then what's the difference between X11's paint engine and QRasterPaintEngine?If the platform also support openGL,then Qt will use X11 API or openGL API?

5,If the GPU support openGL,then Qt may use openGL ;but if the openGL is not support by GPU,then how Qt  treat this situation ?
How does Qt4.8(or the Qt 5) do the painting work?
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It is probably as same as “ How my program code transition to the GUI on screen device via various Qt5 painting system?”  

Since Qt support various kinds of platforms,my questions only base on Linux and Embedded Linux(because both are opensource os and are different in painting :-) )。

My question focus on these topics:

1, Are QWidget ，QGraphicsItem，Rectangle(in QML) different in the painting system?And what is it ?

2, Which one don't use QPaint（QPaintEngine） class ?

3,How many paint engines implemented in Qt4.8(or Qt5)?For example, QRasterPaintEngine.

4,If the platform is Linux(with X11 supported),will Qt use X11 API do the painting?Then what's the difference between X11's paint engine and QRasterPaintEngine?If the platform also support openGL,then Qt will use X11 API or openGL API?

5,If the GPU support openGL,then Qt may use openGL ;but if the openGL is not support by GPU,then how Qt  treat this situation ?