How to support HTML for QGroupBox?

Question

I need to create a group box that supports HTML text when we set

MyGroupBox *gb = new MyGroupBox();
gb->setTitle("<u> This is underlined text</u>");

I have tried some searches but no results. In my head right now I think only about to set style for my groupbox. Something like this:

MyGroupBox.cpp

MyGroupBox::MyGroupBox( QWidget *p_parent ) : QGroupBox( p_parent )
{
  setStyle( &m_style );
}

TitleStyle.hpp

class TitleStyle : public QProxyStyle
{
public:
  TitleStyle() = default;
  virtual void drawComplexControl( ComplexControl control, const QStyleOptionComplex *option, QPainter *painter, const QWidget *widget = nullptr ) const override;
};

TitleStyle.cpp

void TitleStyle::drawComplexControl( ComplexControl p_control, const QStyleOptionComplex *p_option, QPainter *p_painter, const QWidget *p_widget ) const
{
  if ( p_control == CC_GroupBox )
  {
     if ( const QStyleOptionGroupBox *title = qstyleoption_cast<const QStyleOptionGroupBox *>( p_option ) )
     {
           QTextDocument td;
           td.setHtml( title->text );
           td.drawContents( p_painter );
     }
  }
  else
  {
     QProxyStyle::drawComplexControl( p_control, p_option, p_painter, p_widget );
  }
}

This still does not work. I know my drawComplexControl is weird, but that is what in my mind now. Can anyone tell me if I am going in the right direction? If yes, how could I change the class TitleStyle. If not, how could I do?

Solution: It took me a while to find my mistake. With the code above, the title should be rich text supported already.

MainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QProxyStyle>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class TitleStyle : public QProxyStyle
{
public:
    TitleStyle() = default;
    virtual void drawComplexControl( ComplexControl control, const QStyleOptionComplex *option, QPainter *painter, const QWidget *widget = nullptr ) const override;
};

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    TitleStyle m_style;
};
#endif // MAINWINDOW_H

MainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QTextDocument>

void TitleStyle::drawComplexControl( ComplexControl p_control, const QStyleOptionComplex *p_option, QPainter *p_painter, const QWidget *p_widget ) const
{
  if ( p_control == CC_GroupBox )
  {
     if ( const QStyleOptionGroupBox *title = qstyleoption_cast<const QStyleOptionGroupBox *>( p_option ) )
     {
           QTextDocument td;
           td.setHtml( title->text );
           td.drawContents( p_painter );
     }
  }
  else
  {
     QProxyStyle::drawComplexControl( p_control, p_option, p_painter, p_widget );
  }
}

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
, ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->groupBox->setStyle(&m_style);
    ui->groupBox->setTitle("<b><u>This is an underlined title</u></b>");
}

MainWindow::~MainWindow()
{
    delete ui;
}

Result:

Answer 1

Actually I have found my mistake in other positions. With this code, the title should be rich text supported already. I have tried with Qt Creator and it worked. I update my solution above.