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QStyledItemDelegate Class ReferenceThe QStyledItemDelegate class provides display and editing facilities for data items from a model. More... #include <QStyledItemDelegate>Inherits: QAbstractItemDelegate. This class was introduced in Qt 4.4. Public Functions
Reimplemented Public Functions
Protected Functions
Reimplemented Protected Functions
Additional Inherited Members
Detailed DescriptionThe QStyledItemDelegate class provides display and editing facilities for data items from a model. When displaying data from models in Qt item views, e.g., a QTableView, 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. The QStyledItemDelegate class is one of the Model/View Classes and is part of Qt's model/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 an ItemDataRole; each item can store a QVariant 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 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 EditRole that is edited. See the QItemEditorFactory class for a more high-level introduction to item editor factories. The Color Editor Factory example shows how to create custom editors with a factory. Subclassing QStyledItemDelegateIf the delegate does not support painting of the data types you need or you want to customize the drawing of items, you need to subclass QStyledItemDelegate, and reimplement paint() and possibly sizeHint(). The paint() function is called individually for each item, and with sizeHint(), you can specify the hint for each of them. When reimplementing paint(), 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. The QStyle 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 subclass QStyle. Note, however, that the size of the items can also be affected by reimplementing sizeHint(). 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:
The Star Delegate example creates editors by reimplementing these methods. QStyledItemDelegate vs. QItemDelegateSince Qt 4.4, 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 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 the QStyle class documentation for details. See also Delegate Classes, QItemDelegate, QAbstractItemDelegate, QStyle, Spin Box Delegate Example, Star Delegate Example, and Color Editor Factory Example. Member Function Documentation
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