Automate screenshots of QLayout

QLayouts are layout managers, not widgets, therefore they can not be responsible of any rendering at all. Their purpose is to manage the layout of their items, which may not even be widgets to begin with (for instance: spacers).

You can imagine layout managers as contractor managers: they will organize the work necessary to build and put things based on your expectations and needs, while also considering building/safety requirements. They cannot "show" you the final look of the building, as that's not their job. Yet, they can provide means to do that, once they've taken their considerations, while working along with architects and/or project managers.

If you want to "grab" the contents of a specific layout, that layout needs to be properly set on a widget, or added to a parent layout that has been set on a widget on its own; then, when the whole layout has been properly activated, you need to consider the layout.geometry() (which is an overridden function of QLayoutItem.geometry()).

Since QLayout is automatically parented whenever it's set on a widget (either by calling its constructor with the widget as its parent, or by using Q*Layout(widget)) or when added to another layout, you could create a global function that takes the layout and eventually calls render based on the layout geometry().

def captureLayout(layout):
    widget = layout.parentWidget()
    if widget is None:
        return QPixmap()

    # possibly necessary
    widget.ensurePolished()

    geo = layout.geometry()

    # ignore invalid size (width or height less or equal to 0)
    if not geo.isValid():
        return QPixmap()

    grab = QPixmap(geo.size())
    grab.fill(Qt.GlobalColor.transparent)

    qp = QPainter(grab)
    widget.render(qp, region=QRegion(geo))
    qp.end()

    return grab

Note that under certain circumstances the above may not work as expected, or even cause a program crash.