qwidget reports incorrect width value

user4592357

i have such a class

class MyWidget : public QWidget
{
/// ...
};

then i add widgets to a hbox layout, and set thay layout to MyWidget object.
i want MyWidget widget to have the width of a widget contained in it.
so i overrode size hint:

QSize MyWidget::sizeHint() const
{
    // use the width of the first widget in the frame
    if (auto pLayout = layout())
    {
        auto pItem = pLayout->itemAt(0);
        //std::cout << pItem->widget()->width() << std::endl;
        if (pItem && pItem->widget())
            return QSize{ pItem->widget()->width(), QWidget::sizeHint().height() };
    }
    return QWidget::sizeHint();
}

now, pItem->widget()->width() always reports the same value no matter what size the widget is. what's the problem???

mrjj

@user4592357
Hi
If you call pItem->widget()->width() while the inner widget
is not visible, it might not report actual size. ( layout are not calculated yet )
You can try use the ShowEvent instead or
use
layout->invalidate();
layout->activate();
to try to force layout to be calculated before shown.

user4592357

this didn't work, i get the same result:

QSize MyWidget::sizeHint() const
{
	// use the width of the first widget in the frame
	if (auto pLayout = layout())
	{
		auto pItem = pLayout->itemAt(0);
		//std::cout << pItem->widget()->sizeHint().width() << std::endl;
		if (pItem && pItem->widget())
		{
			pLayout->invalidate();
			pLayout->activate();
			return QSize{ pItem->widget()->width(), QWidget::sizeHint().height() };
		}
	}
	return QWidget::sizeHint();
}

and i don't get how i'd use the inner widget sizes in showEvent()

mrjj

Hi
Hmm ok. I did something similar and that worked but i cant spot the difference.
Well try
pItem->widget()->width()
in ShowEvent to see if that even report expected size.

Also if MyWidget is a layout, then layout set size of it.
Unless you set MinimumSize for MyWidget
It will ignore resize / set Geometry.
Also sizeHint is just suggested size but if innner widget is also in a layout, then
om not sure this logic can even work. ( as inner widget then follow outer widget)
So something about this setup confuses me.

user4592357

yes, inner widget has min size set
and in showEvent inner widget still has the same size as before.

mrjj

@user4592357
So it does not report the minimumSize for the inner widget?

user4592357

no, it reports a little big larger, like 12px larger.
also, i have set setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);

p.s. i solved this another way. thanks for helping