Widgets not visible in QGridLayout

kshegunov

Hello,
I've been struggling with a problem for a couple of days now and I'm pretty much at a loss. Here's the relevant code:

void RbDisplayGridLayout::put(const RbGraphWidgetList & list)
{
    layout()->addWidget(new QLabel("test"));  //< Widget shows
    for (int i = 0; i < list.size(); i++)
        layout()->addWidget(list[i]); //< Widget doesn't show
}

The list is defined as:

typedef QVector<RbGraphWidget *> RbGraphWidgetList;

and the RbGraphWidget is just a dummy defined with:

RbGraphWidget::RbGraphWidget(const Graph & meta, QWidget *parent)
    : QWidget(parent), graph(meta)
{
    ui.setupUi(this);

    setWindowTitle(graph.name);
    ui.label->setText(graph.name);
}

The ui.label is a simple QLabel that shows a string, nothing fancy here.

The odd thing is that I can see the dummy widgets just fine if I add them to a QTabWidget, but they don't display when I add them to the QGridLayout.
Did I miss something obvious?

SGaist

Hi,

That looks correct...

Some silly tests:

add one of your custom widget the same way you do with your QLabel before the loop.
create the list of your custom widget in the same method you pass them to your grid layout.

Are these widget used elsewhere ?

What version of Qt are you running ?
On what OS ?

mrjj

@kshegunov said in Widgets not visible in QGridLayout:

RbDisplayGridLayout

Is that a subclass of QGridLayout ?

kshegunov

@SGaist said in Widgets not visible in QGridLayout:

Hi,

Hi. I solved it, but I'm going to add answers to the questions just for posterity.

That looks correct...

It turns out it is correct.

Some silly tests:

add one of your custom widget the same way you do with your QLabel before the loop.

Same result. The first thing I tried.

create the list of your custom widget in the same method you pass them to your grid layout.

Hadn't tested that, but if I had, then I'd have had less gray hair. Your spidey sense is correct.

Are these widget used elsewhere ?

Yes, they're taken out from a QTabWidget as this:

RbGraphWidgetList RbDisplayTabLayout::take()
{
    int size = count();

    RbGraphWidgetList list;
    list.reserve(size);

    for (int i = 0; i < size; i++)
        list.append(reinterpret_cast<RbGraphWidget *>(widget(i)));

    QTabWidget::clear();

    // We need a clean slate before reinserting the widgets into another layout
    for (QWidget * widget : list)
        widget->setParent(nullptr);

    return list;
}

What version of Qt are you running ?

Qt 5.14.x

On what OS ?

Linux (debian testing), but I imagine the windows is going to behave the same.

Now what the problem was and how it is solved:

The problem is that (all) the widgets I get are hidden even the active one (probably by QTabWidget::clear). Calling show on them when I add them to the layout fixes the problem. Why is that isn't exactly clear to me, but it appears to be some idiosyncrasy of the tab widget I was not aware of, nor is it spelled in the docs explicitly.

EDIT:

@mrjj said in Widgets not visible in QGridLayout:

@kshegunov said in Widgets not visible in QGridLayout:

RbDisplayGridLayout

Is that a subclass of QGridLayout ?

No, it's a widget.

mrjj

So basically they were just hidden ?

kshegunov

@mrjj said in Widgets not visible in QGridLayout:

So basically they were just hidden ?

Yes, very much so.

SGaist

Intriguing behaviour !

I thought about suggesting adding a show call but forgot to add it 😅

Nice catch !

osirisgothra

fwiw, late though it may be, i found an odd behavior with some custom widgets requiring you to explicitly set the row/colspan when adding the item (eg, insertWidget(item,row,col,1,1)) -- this does not seem to happen with custom widgets that are a collection of custom controls, just ones that do their own custom painting in paintEvent.