Qt is one of the best GUI Widget cross-platform libraries that I ever worked with 
.
At some point, I was in need for a Combo box with a list of Checkbox item. And that had not been provided as out-of- shelf widget. For some reason, one of them as in the following quotes:
“a combo box is a way to represent a single selection, not to hide other GUI elements”.
First let understand the QComboBox. The Combo box usually has two main parts: current item view and items view (popup) . Current view is view displaying the selected item. While items view display a list of items to be select.
Now let work with the items view to handle item as checkbox rather than a label . In order to customize our items view we need to assignee an item delegate to the items view. And that led us to create a customized (inherited) QItemDelegate let called CheckBoxListDelegate:
class CheckBoxListDelegate : public QItemDelegate
{
public:
CheckBoxListDelegate(QObject *parent)
: QItemDelegate(parent)
{
;
}
void paint(QPainter *painter, const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
//Get item data
bool value = index.data(Qt::UserRole).toBool();
QString text = index.data(Qt::DisplayRole).toString();
// fill style options with item data
const QStyle *style = QApplication::style();
QStyleOptionButton opt;
opt.state |= value ? QStyle::State_On : QStyle::State_Off;
opt.state |= QStyle::State_Enabled;
opt.text = text;
opt.rect = option.rect;
// draw item data as CheckBox
style->drawControl(QStyle::CE_CheckBox,&opt,painter);
}
QWidget *createEditor(QWidget *parent,
const QStyleOptionViewItem & option ,
const QModelIndex & index ) const
{
// create check box as our editor
QCheckBox *editor = new QCheckBox(parent);
return editor;
}
void setEditorData(QWidget *editor,
const QModelIndex &index) const
{
//set editor data
QCheckBox *myEditor = static_cast<QCheckBox*>(editor);
myEditor->setText(index.data(Qt::DisplayRole).toString());
myEditor->setChecked(index.data(Qt::UserRole).toBool());
}
void setModelData(QWidget *editor, QAbstractItemModel *model,
const QModelIndex &index) const
{
//get the value from the editor (CheckBox)
QCheckBox *myEditor = static_cast<QCheckBox*>(editor);
bool value = myEditor->isChecked();
//set model data
QMap<int,QVariant> data;
data.insert(Qt::DisplayRole,myEditor->text());
data.insert(Qt::UserRole,value);
model->setItemData(index,data);
}
void updateEditorGeometry(QWidget *editor,
const QStyleOptionViewItem &option, const QModelIndex &index ) const
{
editor->setGeometry(option.rect);
}
};
Then we need to tell our combo box to use that delegate as default delegate for the items view that it own. Also we need to change the way it display the selected item. Header of our CheckBoxList will look like:
class CheckBoxList: public QComboBox
{
Q_OBJECT;
public:
CheckBoxList(QWidget *widget = 0);
virtual ~CheckBoxList();
bool eventFilter(QObject *object, QEvent *event);
virtual void paintEvent(QPaintEvent *);
void SetDisplayText(QString text);
QString GetDisplayText() const;
private:
QString m_DisplayText;
};
And the implementation:
CheckBoxList::CheckBoxList(QWidget *widget )
:QComboBox(widget),m_DisplayText(0)
{
// set delegate items view
view()->setItemDelegate(new CheckBoxListDelegate(this));
// Enable editing on items view
view()->setEditTriggers(QAbstractItemView::CurrentChanged);
// set "CheckBoxList::eventFilter" as event filter for items view
view()->viewport()->installEventFilter(this);
// it just cool to have it as defualt
view()->setAlternatingRowColors(true);
}
CheckBoxList::~CheckBoxList()
{
;
}
bool CheckBoxList::eventFilter(QObject *object, QEvent *event)
{
// don’t close items view after we release the mouse button
// by simple eating MouseButtonRelease in viewport of items view
if(event->type() == QEvent::MouseButtonRelease && object==view()->viewport())
{
return true;
}
return QComboBox::eventFilter(object,event);
}
void CheckBoxList::paintEvent(QPaintEvent *)
{
QStylePainter painter(this);
painter.setPen(palette().color(QPalette::Text));
// draw the combobox frame, focusrect and selected etc.
QStyleOptionComboBox opt;
initStyleOption(&opt);
// if no display text been set , use "…" as default
if(m_DisplayText.isNull())
opt.currentText = "…";
else
opt.currentText = m_DisplayText;
painter.drawComplexControl(QStyle::CC_ComboBox, opt);
// draw the icon and text
painter.drawControl(QStyle::CE_ComboBoxLabel, opt);
}
void CheckBoxList::SetDisplayText(QString text)
{
m_DisplayText = text;
}
QString CheckBoxList::GetDisplayText() const
{
return m_DisplayText;
}
And that’s it see it in action:
CheckBoxList list;
list.addItem("Qt",true);
list.addItem("CMake",true);
list.addItem("10.99$",false);
list.addItem("Da-Crystal",true);
Unitny is a web service that does the opposite of what ‘tiny’ sites do. It simply returns the original Url for a given shortened Url. Why? Why not use the shortened URL? The main reason is, in some countries, some ISP’s are blocking this kind of sites (tiny sites) for a claim of security issue.
, that annoying message appear for JawalNet users (like me 
).
.
, but that what I ended up of ).
) :
