SetStyleSheet background-color doesn't work on a derived widget

[ReHa1]

If i set a background-color by setStyleSheet() on a QWidget directly that works perfect.
But if i create an own widget, derived by QWidget, the background-color doesn't work in it.
Does anybody have an idea why??? Many Thanks!!!

Here the code which shows the difference:

main.cpp:
@#include <QtGui/QApplication>
#include "mywidgets.h"

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

return a.exec();
}
@

mywidgets.h:
@#include <QWidget>

class MainWidget : public QWidget
{
Q_OBJECT

public:
explicit MainWidget(QWidget *parent = 0);
};

class RedWidget : public QWidget
{
Q_OBJECT

public:
explicit RedWidget(QWidget *parent = 0);
};

class YellowWidget : public QWidget
{
Q_OBJECT

public:
explicit YellowWidget(QWidget *parent = 0);
};@

mywidgets.cpp:
@#include "mywidgets.h"
#include <QHBoxLayout>
#include <QWidget>

RedWidget::RedWidget(QWidget *parent) :
QWidget(parent)
{
this->setStyleSheet("background-color:red");
}

YellowWidget::YellowWidget(QWidget *parent) :
QWidget(parent)
{
this->setStyleSheet("background-color:yellow");
}

MainWidget::MainWidget(QWidget *parent) :
QWidget(parent)
{
this->setMinimumWidth(800);
this->setMinimumHeight(600);
this->setStyleSheet("background-color:grey");

QHBoxLayout* layout = new QHBoxLayout(this);

/*
// This works fine:
QWidget* wYellow = new QWidget(this);
QWidget* wRed = new QWidget(this);
wYellow->setStyleSheet("background-color:yellow");
wRed->setStyleSheet("background-color:red");
*/

// But not this version:
YellowWidget* wYellow = new YellowWidget(this);
RedWidget* wRed = new RedWidget(this);

layout->addWidget(wYellow);
layout->addWidget(wRed);

this->setLayout(layout);

}
@

[dangelog]

Read the documentation for QWidget.

http://doc.qt.nokia.com/4.7/stylesheet-reference.html

[ReHa1]

You mean

---

If you subclass from QWidget, you need to provide a paintEvent for your custom QWidget as below:

@void CustomWidget::paintEvent(QPaintEvent *)
{
QStyleOption opt;
opt.init(this);
QPainter p(this);
style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
}@

The above code is a no-operation if there is no stylesheet set.

Warning: Make sure you define the Q_OBJECT macro for your custom widget.

Yes, thanks - that works.
But i wonder, to have to do such overhead. Why isn't it implemented in QWidget itself?