scroll bars are not appearing

[Cruz]

I have a QFrame dropArea with QHBoxLayout inside a QScrollArea. Now I drop widgets on it with drag and drop.

ui.dropArea->layout()->addWidget(widget);
ui.dropArea->adjustSize();

ui.dropArea->layout()->addWidget(widget);
ui.dropArea->adjustSize();

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I can see the adjustSize() working, the dropArea is growing with every widget I drop. But when it reaches the limit, the scroll bars don't appear like they should. The scroll bar policies are set to the default "as needed" by Designer. What do I need to tweak?