Are the QTabWidget and QTableView drawn based on the top-level window?

[dotboy]

Here is my question:
1. A transparent window(with Qt::Window Flag) has 2 sub-child-widget layouted by QVBoxLayout, and the buttom one has another sub-child-widget QTabWidget which then I put some QTableViews on. ----the structre
2. Back to the top-level window, if I invoke blew:
toplevelWindow->setAutoFillBackground(false); it'll show the window like:
2.jpg(the first image) well transparency, but the Table View was not correct
3. toplevelWindow->setAutoFillBackground(true); it'll show the windowas:
1.jpg(the second image) the Background was painted black by system
I just want the top-level window to be transparent but not child widget...
PlateForm: Windows +qt 4.5.2