setStyleSheet sometimes not working

Jakob Clausen

I have a problem using setStyleSheet() in a widget. I would like to adjust the font size from a stylesheet file. In the two examples, the only difference is the argument for setStyleSheet().
This works

Data::Data(DataBase::Signal index, QString size, QWidget* parent, uint16_t subindex) :
    Button(parent),
    index(index),
    subindex(subindex),
    alive(false)
{
    setAttribute(Qt::WA_StyledBackground);
    setAlignment(Qt::AlignCenter);
    setObjectName(size);

    setStyleSheet("font-size: 26pt;");

    QHBoxLayout* layout = new QHBoxLayout(this);
    icon = new QLabel(this);
    data = new QLabel(this);
    unit = new QLabel(this);
    layout->addWidget(icon);
    layout->addWidget(data);
    layout->addWidget(unit);

    data->setText("0");
}

but

Data::Data(DataBase::Signal index, QString size, QWidget* parent, uint16_t subindex) :
    Button(parent),
    index(index),
    subindex(subindex),
    alive(false)
{
    setAttribute(Qt::WA_StyledBackground);
    setAlignment(Qt::AlignCenter);
    setObjectName(size);

    setStyleSheet("Data#SMALL { font-size: 26pt; }");

    QHBoxLayout* layout = new QHBoxLayout(this);
    icon = new QLabel(this);
    data = new QLabel(this);
    unit = new QLabel(this);
    layout->addWidget(icon);
    layout->addWidget(data);
    layout->addWidget(unit);

    data->setText("0");
}

Does not work.

JonB

@Jakob-Clausen
Have you verified qDebug() << size; for us? We do not know what might or might not be in that.....

Jakob Clausen

Yes. I have.

It can be either "SMALL", "MEDIUM" or "LARGE" and all they do is change the font size.
There is no check to see if the objectname is one of the three.
But in this example I have checked it manually as you suggest, and it is "SMALL".

JonB

@Jakob-Clausen
Try with selector of just Data and/or #SMALL in place of Data#SMALL: any difference? What about with just *?

Jakob Clausen

Thats interesting.

setStyleSheet("Data { font-size: 26pt; }");

or

setStyleSheet("#SMALL { font-size: 26pt; }");

does not work.
Neither does

setStyleSheet("{ font-size: 26pt; }");

But as you suggest

setStyleSheet("* { font-size: 26pt; }");

does.
Does that make any sense?

JonB

@Jakob-Clausen
* is the selector for "anything". This implies to me that none of Data#SMALL, Data or #SMALL correctly address your widget instance, or maybe the right "bit" of it, but I do not know why. What is the ultimate base Qt type of your Data class?

Jakob Clausen

It is derived from QLabel.

JonB

@Jakob-Clausen
setStyleSheet("QLabel { font-size: 26pt; }"); ?

Jakob Clausen

That works! :-)
What does that mean?

JonB

@Jakob-Clausen
One outside thought is: does your Data class use the Q_OBJECT macro in its definition? That is usually required for signals, I have no idea whether that just might be required for stylesheet-widget-inheritance to work, worth checking.

Otherwise, produce the absolute minimum standalone program which creates a QLabel and show setStyleSheet("QLabel { font-size: 26pt; }") working, together with the minimum for a derived MyLabel and show that setStyleSheet("MyLabel { font-size: 26pt; }") does not work.

P.S.
Your Data class does not reside in a namespace, does it??

P.P.S.
I don't know whether this applies to deriving from QLabel, but for deriving from QWidget read https://forum.qt.io/topic/55983/inheritance-from-qwidget-stylesheet-problem & https://stackoverflow.com/questions/7276330/qt-stylesheet-for-custom-widget. But I'm really thinking/pretty sure that applies to QWidget only....

Jakob Clausen

I use Q_OBJECT and it is not in a namespace.
I have also tried to reimplement the event callback without any luck.
Now I will try to create a minimal standalone example.

Jakob Clausen

Ok. I have not yet created the absolute minimum standalone program, but I have something else.
If I do

setStyleSheet("Data QLabel { font-size: 26pt; }")

then it works. :-)
But why? Isn't the stylesheet supposed to be passed along to children automatically? (I guess not).

So Data#SMALL only applies to Data-objects with the name SMALL and not its descendants and Data QLabel applies to all QLabel descendants of Data.
Is what I just wrote correct?

JonB

@Jakob-Clausen
But you said earlier that Data is derived from QLabel (not e.g. that it contains a QLabel)? That's why I asked?

Jakob Clausen

Ah.
Sorry about that.
It does both.

Jakob Clausen

But many thanks for your effort.
I appreciate it.

JonB

@Jakob-Clausen said in setStyleSheet sometimes not working:

It does both.

It is a QLabel, and it also contains (another) QLabel?

P.S.
As a tip/suggestion, don't pick Data as a class name, and certainly not for some GUI element like labels.

Jakob Clausen

Yes.
In a layout.
Is that bad?

Jakob Clausen

@JonB Ok. Thank you.

JonB

@Jakob-Clausen said in setStyleSheet sometimes not working:

Is that bad?

[Nested QLabels.] I don't know, I've never done it!