Contents

• Public Functions
• Reimplemented Public Functions
• Protected Functions
• Reimplemented Protected Functions
• Detailed Description
• Subclassing QStyledItemDelegate
• QStyledItemDelegate vs. QItemDelegate

Detailed Description

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

When displaying data from models in Qt item views, e.g., aQTableView, the individual items are drawn by a delegate. Also, when an item is edited, it provides an editor widget, which is placed on top of the item view while editing takes place.QStyledItemDelegate is the default delegate for all Qt item views, and is installed upon them when they are created.

TheQStyledItemDelegate class is one of theModel/View Classes and is part of Qt'smodel/view framework. The delegate allows the display and editing of items to be developed independently from the model and view.

The data of items in models are assigned anItemDataRole; each item can store aQVariant for each role.QStyledItemDelegate implements display and editing for the most common datatypes expected by users, including booleans, integers, and strings.

The data will be drawn differently depending on which role they have in the model. The following table describes the roles and the data types the delegate can handle for each of them. It is often sufficient to ensure that the model returns appropriate data for each of the roles to determine the appearance of items in views.

Editors are created with aQItemEditorFactory; a default static instance provided byQItemEditorFactory is installed on all item delegates. You can set a custom factory usingsetItemEditorFactory() or set a new default factory withQItemEditorFactory::setDefaultFactory(). It is the data stored in the item model with theEditRole that is edited. See theQItemEditorFactory class for a more high-level introduction to item editor factories. TheColor Editor Factory example shows how to create custom editors with a factory.

Subclassing QStyledItemDelegate

If the delegate does not support painting of the data types you need or you want to customize the drawing of items, you need to subclassQStyledItemDelegate, and reimplementpaint() and possiblysizeHint(). Thepaint() function is called individually for each item, and withsizeHint(), you can specify the hint for each of them.

When reimplementingpaint(), one would typically handle the datatypes one would like to draw and use the superclass implementation for other types.

The painting of check box indicators are performed by the current style. The style also specifies the size and the bounding rectangles in which to draw the data for the different data roles. The bounding rectangle of the item itself is also calculated by the style. When drawing already supported datatypes, it is therefore a good idea to ask the style for these bounding rectangles. TheQStyle class description describes this in more detail.

If you wish to change any of the bounding rectangles calculated by the style or the painting of check box indicators, you can subclassQStyle. Note, however, that the size of the items can also be affected by reimplementingsizeHint().

It is possible for a custom delegate to provide editors without the use of an editor item factory. In this case, the following virtual functions must be reimplemented:

• 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.

TheStar Delegate example creates editors by reimplementing these methods.

QStyledItemDelegate vs. QItemDelegate

Since Qt 4.4, there are two delegate classes:QItemDelegate andQStyledItemDelegate. However, the default delegate isQStyledItemDelegate. These two classes are independent alternatives to painting and providing editors for items in views. The difference between them is thatQStyledItemDelegate uses the current style to paint its items. We therefore recommend usingQStyledItemDelegate as the base class when implementing custom delegates or when working with Qt style sheets. The code required for either class should be equal unless the custom delegate needs to use the style for drawing.

If you wish to customize the painting of item views, you should implement a custom style. Please see theQStyle class documentation for details.

Member Function Documentation

QStyledItemDelegate::QStyledItemDelegate(QObject * parent = 0)

Constructs an item delegate with the givenparent.

QStyledItemDelegate::~QStyledItemDelegate()

Destroys the item delegate.

[virtual]QWidget * QStyledItemDelegate::createEditor(QWidget * parent, constQStyleOptionViewItem & option, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::createEditor().

Returns the widget used to edit the item specified byindex for editing. Theparent widget and styleoption are used to control how the editor widget appears.

See alsoQAbstractItemDelegate::createEditor().

[virtual]QString QStyledItemDelegate::displayText(constQVariant & value, constQLocale & locale) const

This function returns the string that the delegate will use to display theQt::DisplayRole of the model inlocale.value is the value of theQt::DisplayRole provided by the model.

The default implementation uses theQLocale::toString to convertvalue into aQString.

This function is not called for empty model indices, i.e., indices for which the model returns an invalidQVariant.

See alsoQAbstractItemModel::data().

[virtual protected]bool QStyledItemDelegate::editorEvent(QEvent * event,QAbstractItemModel * model, constQStyleOptionViewItem & option, constQModelIndex & index)

Reimplemented fromQAbstractItemDelegate::editorEvent().

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

Reimplemented fromQObject::eventFilter().

Returns true if the giveneditor is a validQWidget and the givenevent is handled; otherwise returns false. The following key press events are handled by default:

• Tab
• Backtab
• Enter
• Return
• Esc

In the case ofTab,Backtab,Enter andReturn key press events, theeditor's data is comitted to the model and the editor is closed. If theevent is aTab key press the view will open an editor on the next item in the view. Likewise, if theevent is aBacktab key press the view will open an editor on theprevious item in the view.

If the event is aEsc key press event, theeditor is closedwithout committing its data.

See alsocommitData() andcloseEditor().

[virtual protected]void QStyledItemDelegate::initStyleOption(QStyleOptionViewItem * option, constQModelIndex & index) const

Initializeoption with the values using the indexindex. This method is useful for subclasses when they need aQStyleOptionViewItem, but don't want to fill in all the information themselves. This function will check the version of theQStyleOptionViewItem and fill in the additional values for aQStyleOptionViewItemV2,QStyleOptionViewItemV3 andQStyleOptionViewItemV4.

See alsoQStyleOption::initFrom().

QItemEditorFactory * QStyledItemDelegate::itemEditorFactory() const

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

See alsosetItemEditorFactory().

[virtual]void QStyledItemDelegate::paint(QPainter * painter, constQStyleOptionViewItem & option, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::paint().

Renders the delegate using the givenpainter and styleoption for the item specified byindex.

This function paints the item using the view'sQStyle.

When reimplementing paint in a subclass. Use theinitStyleOption() to set up theoption in the same way as theQStyledItemDelegate; the option will always be an instance ofQStyleOptionViewItemV4. Please see its class description for information on its contents.

Whenever possible, use theoption while painting. Especially itsrect variable to decide where to draw and itsstate to determine if it is enabled or selected.

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 callQPainter::save() before painting andQPainter::restore() afterwards.

See alsoQItemDelegate::paint(),QStyle::drawControl(), andQStyle::CE_ItemViewItem.

[virtual]void QStyledItemDelegate::setEditorData(QWidget * editor, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::setEditorData().

Sets the data to be displayed and edited by theeditor from the data model item specified by the modelindex.

The default implementation stores the data in theeditor widget'suser property.

See alsoQMetaProperty::isUser().

void QStyledItemDelegate::setItemEditorFactory(QItemEditorFactory * factory)

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

See alsoitemEditorFactory().

[virtual]void QStyledItemDelegate::setModelData(QWidget * editor,QAbstractItemModel * model, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::setModelData().

Gets data from theeditor widget and stores it in the specifiedmodel at the itemindex.

The default implementation gets the value to be stored in the data model from theeditor widget'suser property.

See alsoQMetaProperty::isUser().

[virtual]QSize QStyledItemDelegate::sizeHint(constQStyleOptionViewItem & option, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::sizeHint().

Returns the size needed by the delegate to display the item specified byindex, taking into account the style information provided byoption.

This function uses the view'sQStyle to determine the size of the item.

See alsoQStyle::sizeFromContents() andQStyle::CT_ItemViewItem.

[virtual]void QStyledItemDelegate::updateEditorGeometry(QWidget * editor, constQStyleOptionViewItem & option, constQModelIndex & index) const

Reimplemented fromQAbstractItemDelegate::updateEditorGeometry().

Updates theeditor for the item specified byindex according to the styleoption given.