Setting QWidget into QTableWidget cell causing rendering issue.

Please find the attached reproducer.

Steps to reproduce:
1. Uncomment macro QTABLEWIDGETITEM and comment macro QWIDGET so that QTableWidgetItem is set to each cell by setItem. Run the application and hover cursor over any row. A button appears at the right end of viewport with button covering the underlying contents. It looks perfect.
2. Uncomment macro QWIDGET and comment macro QTABLEWIDGETITEM so that QWidget is set to each cell using setCellWidget. Run the application and hover cursor over any row. A button appears at the right end of viewport. Nevertheless, button is NOT covering the underlying contents. But still, button is functional, i.e. clicking it outputs something. So I guess it is a rendering issue rather than a control logic issue.