My first combobox does not react to the mouse

[feraudyh]

Now I think I know what was going on:
I had added a "drawing widget" to the layout of the window programmatically. I created it from a class derived from QLabel so as to draw on, with extra methods, then I added it to the layout programmatically.
I did not think that I could use widgets derived from classes with QtDesigner. I still dont know.
on the other hand the combo box was drawn with QtDesigner, with no consideration for the layout. Yes that's not respectful.
Probably the "drawing label" widget was taking up the whole screen and the combobox was being masked. Now I'm adding the combobox by program, but it appears to the side of the label, halfway between the top and the bottom of the window, which is not ideal. At least it is responding.

[Radek]

The combo box has signals which need to be connected somewhere. The signals which could interest you are activated() and currentIndexChanged(). Depending on the relation of the combo box to the rest of your UI, there could be some default connecting but it need not suit you. This might be the reason why the combo box reacts sometimes and it does not do other times.

Create signal handlers for the combo box, connect and place breaks in the handlers. Debug and see whether your handlers are called and whether the handlers do what they should do.

[ChrisW67]

I did not think that I could use widgets derived from classes with QtDesigner. I still dont know.

Look at the section "Using Custom Widgets with Qt Designer" or search for "promote" in the Qt Designer manual

For vertical placement of the combo box in its horizontal layout space have a look at the alignment options on the right-click context menu for the widget in Designer.

[feraudyh]

Thanks Chris, that's very useful.