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

[dotboy]

No, didn't you see the tab is not showing correctly, and If you put a qtableView on the tabWidget, it'll also get itself shown correctly...
And about mouse handling, I'm dealing with that yet...

And you can compare the jpgs that I uploaded before, there is something different between the 2 QTableView. Around the Lable, one of them has color as the QPalette::Background, but the other one is looks like white.
In the project you build, you can click the tab to see what will happen...

[wysota]

Look... apparently my interpretation of a "minimal compilable example reproducing the problem" and yours differ greatly. I'm not going to read through serveral hundred lines of code with texts I don't understand to find a solution to a problem I don't see. Please provide a minimal compilable example clearly reproducing the problem, at most 100 lines of code in a total of one class plus the main function. Currently you have provided a bunch of classes that intend to do something but it is far from being clear what they do, how they are activated, etc.