CopperSpice API  1.7.2
QItemDelegate Class Reference

The QItemDelegate class provides display and editing facilities for data items from a model. More...

Inheritance diagram for QItemDelegate:
QAbstractItemDelegate QObject QSqlRelationalDelegate

Public Methods

 QItemDelegate (QObject *parent=nullptr)
 
 ~QItemDelegate ()
 
QWidgetcreateEditor (QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const override
 
bool hasClipping () const
 
QItemEditorFactoryitemEditorFactory () const
 
void paint (QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override
 
void setEditorData (QWidget *editor, const QModelIndex &index) const override
 
void setItemEditorFactory (QItemEditorFactory *factory)
 
void setModelData (QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const override
 
QSize sizeHint (const QStyleOptionViewItem &option, const QModelIndex &index) const override
 
void updateEditorGeometry (QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const override
 
- Public Methods inherited from QAbstractItemDelegate
 QAbstractItemDelegate (QObject *parent=nullptr)
 
virtual ~QAbstractItemDelegate ()
 
virtual void destroyEditor (QWidget *editor, const QModelIndex &index) const
 
virtual bool helpEvent (QHelpEvent *event, QAbstractItemView *view, const QStyleOptionViewItem &option, const QModelIndex &index)
 
- Public Methods inherited from QObject
 QObject (QObject *parent=nullptr)
 
 ~QObject ()
 
bool blockSignals (bool block)
 
const QList< QObject * > & children () const
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
void dumpObjectInfo ()
 
void dumpObjectTree ()
 
QList< QStringdynamicPropertyNames () const
 
virtual bool event (QEvent *event)
 
template<typename T >
findChild (const QString &childName=QString ()) const
 
template<class T >
QList< T > findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
template<class T >
QList< T > findChildren (const QString &objName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
bool inherits (const QString &className) const
 
void installEventFilter (QObject *filterObj)
 
bool isWidgetType () const
 
bool isWindowType () const
 
void killTimer (int id)
 
const QMetaObjectmetaObject () const
 
void moveToThread (QThread *targetThread)
 
QString objectName () const
 
QObject * parent () const
 
template<class T = QVariant>
property (const QString &name) const
 
void removeEventFilter (QObject *obj)
 
void setObjectName (const QString &name)
 
void setParent (QObject *parent)
 
bool setProperty (const QString &name, const QVariant &value)
 
bool signalsBlocked () const
 
int startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
 
QThreadthread () const
 

Protected Methods

void drawBackground (QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
 
virtual void drawCheck (QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect, Qt::CheckState state) const
 
virtual void drawDecoration (QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect, const QPixmap &pixmap) const
 
virtual void drawDisplay (QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect, const QString &text) const
 
virtual void drawFocus (QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect) const
 
bool editorEvent (QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index) override
 
bool eventFilter (QObject *object, QEvent *event) override
 
- Protected Methods inherited from QObject
virtual void childEvent (QChildEvent *event)
 
virtual void connectNotify (const QMetaMethod &signalMethod) const
 
virtual void customEvent (QEvent *event)
 
virtual void disconnectNotify (const QMetaMethod &signalMethod) const
 
bool isSignalConnected (const QMetaMethod &signalMethod) const
 
int receivers (const QString &signal) const
 
QObject * sender () const
 
int senderSignalIndex () const
 
virtual void timerEvent (QTimerEvent *event)
 

Properties

 clipping
 
- Properties inherited from QObject
 objectName
 

Additional Inherited Members

- Public Types inherited from QAbstractItemDelegate
enum  EndEditHint
 
- Public Signals inherited from QAbstractItemDelegate
void closeEditor (QWidget *editor, QAbstractItemDelegate::EndEditHint hint=NoHint)
 
void commitData (QWidget *editor)
 
void sizeHintChanged (const QModelIndex &index)
 
- Public Signals inherited from QObject
void destroyed (QObject *obj=nullptr)
 
void objectNameChanged (const QString &objectName)
 
- Public Slots inherited from QObject
void deleteLater ()
 
- Static Public Methods inherited from QAbstractItemDelegate
static QString elidedText (const QFontMetrics &fontMetrics, int width, Qt::TextElideMode mode, const QString &text)
 
- Static Public Methods inherited from QObject
static bool connect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool connect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())
 
static bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool disconnect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...))
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)
 
static QMetaObjectstaticMetaObject ()
 
static QString tr (const char *text, const char *comment=nullptr, std::optional< int > numArg=std::optional< int >())
 

Detailed Description

The QItemDelegate class provides display and editing facilities for data items from a model.

QItemDelegate can be used to provide custom display features and editor widgets for item views based on QAbstractItemView subclasses. Using a delegate for this purpose allows the display and editing mechanisms to be customized and developed independently from the model and view.

The QItemDelegate class is one of the Model/View Classes and is part of the CopperSpice Model/View Programming. Note the QStyledItemDelegate has taken over the job of drawing the CopperSpice item views. We recommend using the QStyledItemDelegate when creating new delegates.

When displaying items from a custom model in a standard view, it is often sufficient to simply ensure that the model returns appropriate data for each of the roles which determine the appearance of items in views. The default delegate used by the CopperSpice standard views uses this role information to display items in most of the common forms expected by users. However, it is sometimes necessary to have even more control over the appearance of items than the default delegate can provide.

This class provides default implementations of the functions for painting item data in a view and editing data from item models. Default implementations of the paint() and sizeHint() virtual functions, defined in QAbstractItemDelegate, are provided to ensure that the delegate implements the correct basic behavior expected by views. You can reimplement these functions in subclasses to customize the appearance of items.

When editing data in an item view, QItemDelegate provides an editor widget, which is a widget that is placed on top of the view while editing takes place. Editors are created with a QItemEditorFactory; a default static instance provided by QItemEditorFactory is installed on all item delegates. You can set a custom factory using setItemEditorFactory() or set a new default factory with QItemEditorFactory::setDefaultFactory(). It is the data stored in the item model with the Qt::EditRole that is edited.

Only the standard editing functions for widget-based delegates are reimplemented here:

  • createEditor() returns the widget used to change data from the model and can be reimplemented to customize editing behavior.
  • setEditorData() provides the widget with data to manipulate.
  • updateEditorGeometry() ensures that the editor is displayed correctly with respect to the item view.
  • setModelData() returns updated data to the model.

The closeEditor() signal indicates that the user has completed editing the data, and that the editor widget can be destroyed.

Standard Roles and Data Types

The default delegate used by the standard views supplied with CopperSpice associates each standard role (defined by Qt::ItemDataRole) with certain data types. Models that return data in these types can influence the appearance of the delegate as described in the following table.

RoleAccepted Types
Qt::BackgroundRoleQBrush
Qt::BackgroundColorRoleQColor (obsolete, use Qt::BackgroundRole instead)
Qt::CheckStateRoleQt::CheckState
Qt::DecorationRoleQIcon, QPixmap and QColor
Qt::DisplayRoleQString and types with a string representation
Qt::EditRoleSee QItemEditorFactory for details
Qt::FontRoleQFont
Qt::SizeHintRoleQSize
Qt::TextAlignmentRoleQt::Alignment
Qt::ForegroundRoleQBrush
Qt::TextColorRoleQColor (obsolete, use Qt::ForegroundRole instead)

If the default delegate does not allow the level of customization that you need, either for display purposes or for editing data, it is possible to subclass QItemDelegate to implement the desired behavior.

Subclassing

When subclassing QItemDelegate to create a delegate that displays items using a custom renderer, it is important to ensure that the delegate can render items suitably for all the required states; e.g. selected, disabled, checked. The documentation for the paint() function contains some hints to show how this can be achieved.

You can provide custom editors by using a QItemEditorFactory. There is no need to subclass QItemDelegate. An alternative is to reimplement createEditor(), setEditorData(), setModelData(), and updateEditorGeometry().

QStyledItemDelegate vs. QItemDelegate

There are two delegate classes: QItemDelegate and QStyledItemDelegate. However, the default delegate is QStyledItemDelegate. These two classes are independent alternatives to painting and providing editors for items in views. The difference between them is that QStyledItemDelegate uses the current style to paint its items. We therefore recommend using QStyledItemDelegate as the base class when implementing custom delegates or when working with CopperSpice style sheets. The code required for either class should be equal unless the custom delegate needs to use the style for drawing.

See also
<Delegate Classes, QStyledItemDelegate, QAbstractItemDelegate

Constructor & Destructor Documentation

QItemDelegate::QItemDelegate ( QObject parent = nullptr)
explicit

Constructs an item delegate with the given parent.

QItemDelegate::~QItemDelegate ( )

Destroys the item delegate.

Method Documentation

QWidget * QItemDelegate::createEditor ( QWidget parent,
const QStyleOptionViewItem option,
const QModelIndex index 
) const
overridevirtual

Reimplemented from QAbstractItemDelegate::createEditor(). Returns the widget used to edit the item specified by index for editing. The parent widget and style option are used to control how the editor widget appears.

See also
QAbstractItemDelegate::createEditor()

Reimplemented from QAbstractItemDelegate.

Reimplemented in QSqlRelationalDelegate.

void QItemDelegate::drawBackground ( QPainter painter,
const QStyleOptionViewItem option,
const QModelIndex index 
) const
protected

Renders the item background for the given index, using the given painter and style option.

void QItemDelegate::drawCheck ( QPainter painter,
const QStyleOptionViewItem option,
const QRect rect,
Qt::CheckState  state 
) const
protectedvirtual

Renders a check indicator within the rectangle specified by rect, using the given painter and style option, using the given state.

void QItemDelegate::drawDecoration ( QPainter painter,
const QStyleOptionViewItem option,
const QRect rect,
const QPixmap pixmap 
) const
protectedvirtual

Renders the decoration pixmap within the rectangle specified by rect using the given painter and style option.

void QItemDelegate::drawDisplay ( QPainter painter,
const QStyleOptionViewItem option,
const QRect rect,
const QString text 
) const
protectedvirtual

Renders the item view text within the rectangle specified by rect using the given painter and style option.

void QItemDelegate::drawFocus ( QPainter painter,
const QStyleOptionViewItem option,
const QRect rect 
) const
protectedvirtual

Renders the region within the rectangle specified by rect, indicating that it has the focus, using the given painter and style option.

bool QItemDelegate::editorEvent ( QEvent event,
QAbstractItemModel model,
const QStyleOptionViewItem option,
const QModelIndex index 
)
overrideprotectedvirtual

Reimplemented from QAbstractItemDelegate::editorEvent().

Reimplemented from QAbstractItemDelegate.

bool QItemDelegate::eventFilter ( QObject object,
QEvent event 
)
overrideprotectedvirtual

Returns true if the given object is a valid QWidget and the given event is handled, otherwise returns false. The following key press events are handled by default:

  • Tab
  • Backtab
  • Enter
  • Return
  • Esc

In the case of Tab, Backtab, Enter and Return key press events, the editor's data is committed to the model and the editor is closed. If the event is a Tab key press the view will open an editor on the next item in the view. Likewise, if the event is a Backtab key press the view will open an editor on the previous item in the view.

If the event is a Esc key press event, the editor is closed without committing its data.

See also
commitData(), closeEditor()

Reimplemented from QObject.

bool QItemDelegate::hasClipping ( ) const

Property documentation pending.

QItemEditorFactory * QItemDelegate::itemEditorFactory ( ) const

Returns the editor factory used by the item delegate. If no editor factory is set, the function will return null.

See also
setItemEditorFactory()
void QItemDelegate::paint ( QPainter painter,
const QStyleOptionViewItem option,
const QModelIndex index 
) const
overridevirtual

Reimplemented from QAbstractItemDelegate::paint().

Renders the delegate using the given painter and style option for the item specified by index.

When reimplementing this function in a subclass, you should update the area held by the option's rect variable, using the option's state variable to determine the state of the item to be displayed, and adjust the way it is painted accordingly.

For example, a selected item may need to be displayed differently to unselected items, as shown in the following code:

if (option.state & QStyle::State_Selected) {
painter->fillRect(option.rect, option.palette.highlight());
}
int size = qMin(option.rect.width(), option.rect.height());
int brightness = index.model()->data(index, Qt::DisplayRole).toInt();
double radius = (size/2.0) - (brightness/255.0 * size/2.0);
if (radius == 0.0) {
return;
}
painter->save();
painter->setRenderHint(QPainter::Antialiasing, true);
painter->setPen(Qt::NoPen);
if (option.state & QStyle::State_Selected) {
painter->setBrush(option.palette.highlightedText());
} else {
...
}

After painting, you should ensure that the painter is returned to its the state it was supplied in when this function was called. For example, it may be useful to call QPainter::save() before painting and QPainter::restore() afterwards.

See also
QStyle::State

Implements QAbstractItemDelegate.

void QItemDelegate::setEditorData ( QWidget editor,
const QModelIndex index 
) const
overridevirtual

Sets the data to be displayed and edited by the editor from the data model item specified by the model index. The default implementation stores the data in the editor widget's userproperty".

See also
QMetaProperty::isUser()

Reimplemented from QAbstractItemDelegate.

Reimplemented in QSqlRelationalDelegate.

void QItemDelegate::setItemEditorFactory ( QItemEditorFactory factory)

Sets the editor factory to be used by the item delegate to be the factory specified. If no editor factory is set, the item delegate will use the default editor factory.

See also
itemEditorFactory()
void QItemDelegate::setModelData ( QWidget editor,
QAbstractItemModel model,
const QModelIndex index 
) const
overridevirtual

Gets data from the editor widget and stores it in the specified model at the item index. The default implementation gets the value to be stored in the data model from the editor widget's user property.

See also
QMetaProperty::isUser()

Reimplemented from QAbstractItemDelegate.

Reimplemented in QSqlRelationalDelegate.

QSize QItemDelegate::sizeHint ( const QStyleOptionViewItem option,
const QModelIndex index 
) const
overridevirtual

Returns the size needed by the delegate to display the item specified by index, taking into account the style information provided by option. When reimplementing this method for text items QItemDelegate adds a margin of 2 * QStyle::PM_FocusFrameHMargi) to the length of the text.

Implements QAbstractItemDelegate.

void QItemDelegate::updateEditorGeometry ( QWidget editor,
const QStyleOptionViewItem option,
const QModelIndex index 
) const
overridevirtual

Updates the editor for the item specified by index according to the style option given.

Reimplemented from QAbstractItemDelegate.

Property Documentation

QItemDelegate::clipping

This property holds if the delegate should clip the paint events.

This property will set the paint clip to the size of the item. The default value is on. It is useful for cases such as when images are larger than the size of the item.

PropertiesClass Methods
read hasClipping
write setClipping