Setting the background color of widget inside another widget

[Smeeth]

*I am trying to write a very simple application that creates an application with a colored widget at the top of the screen. But all I get is a white screen.

I create the InnerWidget and set its minimum size to 1280x70. Then I use the style sheet to set the background color to black.*

#include "innerwidget.h"
#include <QStyle>

InnerWidget::InnerWidget(QWidget *parent) : QWidget(parent)
{
    setMinimumSize(1280,70);
    this->setStyleSheet("background-color: black");
}

Then, in OuterWidget, I create the InnerWidget and add it to the OuterWidget in a QGridLayout.

#include "outerwidget.h"
#include <QGridLayout>

OuterWidget::OuterWidget(QWidget *parent)
    : QWidget(parent)
{
    innerWidget = new InnerWidget(this);
    QGridLayout *layout = new QGridLayout;
    layout->addWidget(innerWidget, 0, 0, 0, 4, Qt::AlignTop);
    this->setLayout(layout);
    this->setWindowState(Qt::WindowFullScreen);
}

OuterWidget::~OuterWidget()
{

}

My main.cpp just creates the OuterWidget and shows it.

#include "outerwidget.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    OuterWidget w;
    w.show();

    return a.exec();
}

Why is the InnerWidget not appearing on the screen? Am I using the stylesheets or the layout incorrectly?

Thank you.

[JonB]

@Smeeth
100% guess: this->setStyleSheet("background-color: black"); does it matter that you don't have a ; after black?

[Smeeth]

@JonB Thanks for the comment. I have tried adding the ";", but when I do I get a "Could not parse stylsheet of object _____" error and the screen looks the same. I think the reason the semi-colon is not needed is because I am not using a selector, I don't need to use a semicolon to mark the end of the statement.

[JonB]

@Smeeth
While you're waiting for someone more observant/useful than I am :), if you get rid of the QGridLayout does it make any difference? That's what I'd try next....

[Smeeth]

@JonB I appreciate your suggestions! I switched to a simple QVBoxLayout but the problem persists.

[JonB]

@Smeeth
So you can eliminate the QGridLayout from the problem....

...Let's eliminate the InnerWidget code. Replace it with, I don't know, a QPushButon or something. Does that end up appearing?

[Smeeth]

@Smeeth I should note that when I add a control to the InnerWidget, it appears and has a black background. For example, I added the following code inside InnerWidget.

QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(new QLabel());

The QLabel appears in the middle of form and fills almost the whole screen with black (minus what I assume is the default margins or padding of the OuterWidget)

[JonB]

@Smeeth
You and @skebanga are working on the same code?
https://forum.qt.io/topic/91920/setstylesheet-on-qwidget-does-not-have-effect

[skebanga]

@JonB @Smeeth asked the question on SO, and I found setting the stylesheet on the parentWidget worked.

He asked why and I couldn't answer, hence turning to this forum