QItemDelegate Class Reference
[QtGui module]

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. The Color Editor Factory Example shows how a custom editor can be made available to delegates with the default item editor factory. This way, there is no need to subclass QItemDelegate. An alternative is to reimplement createEditor(), setEditorData(), setModelData(), and updateEditorGeometry(). This process is described in the Spin Box Delegate example.

See also Delegate Classes, QStyledItemDelegate, QAbstractItemDelegate, Spin Box Delegate Example, Settings Editor Example, and Icons Example.

Property Documentation

clipping : bool

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.

This property was introduced in Qt 4.2.

Access functions:

• bool hasClipping () const
• void setClipping ( bool clip )

Member Function Documentation

QItemDelegate::QItemDelegate ( QObject * parent = 0 )

Constructs an item delegate with the given parent.

QItemDelegate::~QItemDelegate ()

Destroys the item delegate.

QWidget * QItemDelegate::createEditor ( QWidget * parent, const QStyleOptionViewItem & option, const QModelIndex & index ) const   [virtual]

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.

Reimplemented from QAbstractItemDelegate.

See also QAbstractItemDelegate::createEditor().

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.

This function was introduced in Qt 4.2.

void QItemDelegate::drawCheck ( QPainter * painter, const QStyleOptionViewItem & option, const QRect & rect, Qt::CheckState state ) const   [virtual protected]

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   [virtual protected]

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   [virtual protected]

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   [virtual protected]

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

bool QItemDelegate::eventFilter ( QObject * editor, QEvent * event )   [virtual protected]

Returns true if the given editor 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 comitted 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.

Reimplemented from QObject.

See also commitData() and closeEditor().

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   [virtual]

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.

Reimplemented from QAbstractItemDelegate.

See also QStyle::State.

void QItemDelegate::setEditorData ( QWidget * editor, const QModelIndex & index ) const   [virtual]

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 user property.

Reimplemented from QAbstractItemDelegate.

See also QMetaProperty::isUser().

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   [virtual]

Gets data drom 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.

Note that the model parameter is redundant because the index knows about its model.

Reimplemented from QAbstractItemDelegate.

See also QMetaProperty::isUser().

QSize QItemDelegate::sizeHint ( const QStyleOptionViewItem & option, const QModelIndex & index ) const   [virtual]

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 function, note that in case of text items, QItemDelegate adds a margin (i.e. 2 * QStyle::PM_FocusFrameHMargin) to the length of the text.

Reimplemented from QAbstractItemDelegate.

void QItemDelegate::updateEditorGeometry ( QWidget * editor, const QStyleOptionViewItem & option, const QModelIndex & index ) const   [virtual]

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

Reimplemented from QAbstractItemDelegate.