I've written a simple "proxy widget" class in Qt; the idea is that this widget will hold a single child QWidget and represent that widget in the QWidget hierarchy. (FWIW, the motivation for doing this is to make it easy to

#include <QApplication>
#include <QStackedLayout>
#include <QWidget>

class ProxyWidget : public QWidget
{
public:
   ProxyWidget(QWidget * childWidget)
      : _childWidget(childWidget)
      , _layout(new QStackedLayout(this))
   {
      _layout->addWidget(childWidget);
      setSizePolicy(childWidget->sizePolicy());
   }

   virtual QSize sizeHint() const {return _childWidget->sizeHint();}
   virtual QSize minimumSizeHint() const {return _childWidget->minimumSizeHint();}

private:
   QWidget * _childWidget;
   QStackedLayout * _layout;
};

static void SetWidgetBackgroundColor(QWidget * w, const QColor bc)
{
   QPalette p = w->palette();
   p.setColor(QPalette::Window, bc);
   w->setAutoFillBackground(true);
   w->setPalette(p);
}

int main(int argc, char ** argv)
{
   QApplication app(argc, argv);

   QWidget * win = new QWidget;
   win->setWindowTitle("Proxy Widget test");

   QWidget * proxyMe = new QWidget;
   proxyMe->setFixedSize(100, 50);
   SetWidgetBackgroundColor(proxyMe, Qt::blue);

   QBoxLayout * winLayout = new QBoxLayout(QBoxLayout::TopToBottom, win);

   if ((argc >= 2)&&(strcmp(argv[1], "proxy") == 0))
   {
      ProxyWidget * proxyWidget = new ProxyWidget(proxyMe);
      SetWidgetBackgroundColor(proxyWidget, Qt::red);

      winLayout->addWidget(proxyWidget);
   }
   else winLayout->addWidget(proxyMe);

   win->show();
   return app.exec();
}

CodePudding user response：

I guess minimumSize and maximumSize of ProxyWidget is different from its child widget and setting them fix things in your particular example :

ProxyWidget(QWidget * childWidget)
        : _childWidget(childWidget)
        , _layout(new QStackedLayout(this))
    {
        _layout->addWidget(childWidget);
        setSizePolicy(childWidget->sizePolicy());

        this->setMinimumSize(childWidget->minimumSize());
        this->setMaximumSize(childWidget->maximumSize());
    }

However i am not sure it's the best solution but it might gives you a hint to a better one.