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QtopiaItemDelegate Class Reference

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

    #include <QtopiaItemDelegate>

Inherits QItemDelegate.

Public Functions

Protected Functions

Additional Inherited Members


Detailed Description

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

QtopiaItemDelegate 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 QtopiaItemDelegate class is one of the Model/View Classes.

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 that determine the appearance of items in views. The default delegate used by Qt's 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 obtained from a model with the Qtopia look and feel.

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.

Delegates can be used to manipulate item data in two complementary ways: by processing events in the normal manner, or by implementing a custom editor widget. The item delegate takes the approach of providing a widget for editing purposes that can be supplied to QAbstractItemView::setDelegate() or the equivalent function in subclasses of QAbstractItemView.

Only the standard editing functions for widget-based delegates are reimplemented here: editor() returns the widget used to change data from the model; setEditorData() provides the widget with data to manipulate; updateEditorGeometry() ensures that the editor is displayed correctly with respect to the item view; setModelData() returns the updated data to the model; releaseEditor() 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 Qt associates each standard role (defined by Qt::ItemDataRole and Qtopia::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 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 QtopiaItemDelegate to implement the desired behavior.

Subclassing

When subclassing QtopiaItemDelegate 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.

Custom editing features for can be added by subclassing QtopiaItemDelegate and reimplementing createEditor(), setEditorData(), setModelData(), and updateEditorGeometry(). This process is described in the Spin Box Delegate example.

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


Member Function Documentation

QtopiaItemDelegate::QtopiaItemDelegate ( QObject * parent = 0 )

Constructs an item delegate with the given parent.

QtopiaItemDelegate::~QtopiaItemDelegate ()

Destroys the item delegate.

void QtopiaItemDelegate::drawAdditionalDecoration ( QPainter * painter, const QStyleOptionViewItem & option, const QRect & rect, const QVariant & decoration ) const   [virtual protected]

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

void QtopiaItemDelegate::drawBackground ( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const   [virtual protected]

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

void QtopiaItemDelegate::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.

Reimplemented from QItemDelegate.

void QtopiaItemDelegate::drawDecoration ( QPainter * painter, const QStyleOptionViewItem & option, const QRect & rect, const QPixmap & pixmap ) const   [virtual protected]

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

Reimplemented from QItemDelegate.

void QtopiaItemDelegate::drawDecoration ( QPainter * painter, const QStyleOptionViewItem & option, const QRect & rect, const QVariant & decoration ) const   [virtual protected]

This is an overloaded member function, provided for convenience.

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

void QtopiaItemDelegate::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.

Reimplemented from QItemDelegate.

void QtopiaItemDelegate::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.

Reimplemented from QItemDelegate.

bool QtopiaItemDelegate::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:

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().

void QtopiaItemDelegate::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.

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.

QSize QtopiaItemDelegate::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, QtopiaItemDelegate adds a margin (i.e. 2 * QStyle::PM_FocusFrameHMargin) to the length of the text.

Reimplemented from QAbstractItemDelegate.


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Qtopia 4.3.3