QTreeWidget, resizing item and widgets problem

[wysota]

@wysota
1. I don't use QItemDelegate,

Of course you do. Each cell is painted using a delegate and the default delegate is QItemDelegate or QStyledItemDelegate since Qt 4.4.

2. I use setAutofillBackground(true) to my QFrame widget if it's that whats you meant but no change...

Try changing the palette of the frame (especially the Window role) to see if the background of the frame gets painted.