QCombobox header item

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1 Header item in qcombobox

Header item in qcombobox

Just simple example how to make header item in qcombobox list. This method should also adopted for qcombobox.

How it's implemented

I had to extend two classes QItemDelegate and QStandardItemModel

QItemDelegate extended class

Class header

 
#ifndef DELEGATE_H
#define DELEGATE_H
 
#include <QItemDelegate>
 
// Delegate reimplamentation
class HeaderComboboxBoxDelegate : public QItemDelegate
{
    Q_OBJECT
 
public:
    HeaderComboboxBoxDelegate(QObject *parent = 0);
	void paint(QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index) const;
};
 
#endif

Class implementation

 
#include <QModelIndex>
#include <QPainter>
 
#include "headerdelegate.h"
 
// Constructor
HeaderComboboxBoxDelegate::HeaderComboboxBoxDelegate(QObject *parent)
    : QItemDelegate(parent)
{
	//qDebug("Constructor delegate called");
}
 
 
// Paint reimplementation to show it as header item
void HeaderComboboxBoxDelegate::paint(QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index) const
{
 
	// Current value text
	QString valueString = index.model()->data(index, Qt::DisplayRole).toString();
 
 
	// If item is disabled draw it as header item
	if ( !(index.model()->flags(index) & Qt::ItemIsEnabled))
	{
		// Make bold italic font like in html
		QFont *fontBold = new QFont();
		fontBold->setBold(true);
		fontBold->setItalic(true);
		painter->setFont(*fontBold);		
 
		// Fill background grey color
		QPalette::ColorGroup cg = QPalette::Disabled;
		cg = QPalette::Inactive;
        painter->fillRect(option.rect, option.palette.brush(cg, QPalette::Highlight));
 
		// Draw it
		painter->drawText(option.rect, Qt::AlignLeft | Qt::TextSingleLine,valueString);
 
	}	
	else
	QItemDelegate::paint (painter, option, index);
}

QStandardItemModel extended class

class header

 
#ifndef HEADER_MODEL_H
#define HEADER_MODEL_H
 
#include <QAbstractItemModel>
#include <QStandardItemModel>
 
/**
* Reimplement StandartItemModel with disable item (header item) feature
*/
class HeaderModel : public QStandardItemModel
{
public:
    HeaderModel(QObject *parent = 0);
    Qt::ItemFlags flags(const QModelIndex & index) const;   
};
#endif

Class implementation

 
 
#include "headermodel.h"
 
HeaderModel::HeaderModel(QObject *parent) : QStandardItemModel(parent)
{
	//qDebug("Constructor model called called");
}
 
/**
* Lets change some flags to disable group box item in combobox.
*/
Qt::ItemFlags HeaderModel::flags(const QModelIndex & index) const
{
        Qt::ItemFlags flags = QStandardItemModel::flags(index);
 
       if (!index.isValid())
            return flags;
 
        // I do not now is it the best way to do it, but for me it works.
		QString value =	index.data(Qt::UserRole).toString();
		if (value == "groupbox")
		{
			flags &= ~Qt::ItemIsSelectable;
			flags &= ~Qt::ItemIsEnabled;
		}
 
        return flags;
 }

Main file

 
#include <QApplication>
#include <QHBoxLayout>
#include <QComboBox>
 
//Delegate and model
#include "headerdelegate.h"
#include "headermodel.h"
 
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QWidget *window = new QWidget;
    window->setWindowTitle("Header combobox");
 
    QHBoxLayout *layout = new QHBoxLayout;    
	QComboBox *box = new QComboBox();
 
	HeaderComboboxBoxDelegate delegate;
	box->setModel(new HeaderModel());
	box->setItemDelegate(&delegate);
 
	/******************/
	box->addItem("Normal item");
	box->addItem("Header item","groupbox");
	box->addItem("normal item");
	box->addItem("normal item");
	box->addItem("not group box");
 
	//Make item group box
	box->setItemData(4,"groupbox");
 
	layout->addWidget(box);
    window->setLayout(layout);
    window->show();
 
    return app.exec();
}