No-one noticed that a read only combobox with the list automatically appearing immediately when the widget shows is pretty much a listbox. When I started with this project I used a listbox but found that implementing updateEditorGeometry() was a pain for a listbox delegate. For a combobox you only need to calculate the geometry for the line edit portion (you already have the gemometry for the table cell) and the widget calculates the geometry for the list automatically. I think I'll go back to looking at a listbox.