QStyledItemDelegate

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

Inheritance diagram of PySide2.QtWidgets.QStyledItemDelegate

Synopsis

Functions

Virtual functions

Detailed Description

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.

Role

Accepted Types

BackgroundRole

QBrush (

BackgroundColorRole

QColor (obsolete; use BackgroundRole instead)

CheckStateRole

CheckState

DecorationRole

QIcon , QPixmap , QImage and QColor

DisplayRole

QString and types with a string representation

EditRole

See QItemEditorFactory for details

FontRole

QFont

SizeHintRole

QSize

TextAlignmentRole

Alignment

ForegroundRole

QBrush (

TextColorRole

QColor (obsolete; use ForegroundRole instead)

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 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 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 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:

  • 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 Star Delegate example creates editors by reimplementing these methods.

QStyledItemDelegate vs. QItemDelegate

Since 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 Color Editor Factory Example

class PySide2.QtWidgets.QStyledItemDelegate([parent=None])
param parent:

PySide2.QtCore.QObject

Constructs an item delegate with the given parent .

PySide2.QtWidgets.QStyledItemDelegate.displayText(value, locale)
Parameters:
Return type:

str

This function returns the string that the delegate will use to display the DisplayRole of the model in locale . value is the value of the DisplayRole provided by the model.

The default implementation uses the toString to convert value into a QString .

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

See also

data()

PySide2.QtWidgets.QStyledItemDelegate.initStyleOption(option, index)
Parameters:

Initialize option with the values using the index index . This method is useful for subclasses when they need a QStyleOptionViewItem , but don’t want to fill in all the information themselves.

See also

initFrom()

PySide2.QtWidgets.QStyledItemDelegate.itemEditorFactory()
Return type:

PySide2.QtWidgets.QItemEditorFactory

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

See also

setItemEditorFactory()

PySide2.QtWidgets.QStyledItemDelegate.setItemEditorFactory(factory)
Parameters:

factory – PySide2.QtWidgets.QItemEditorFactory

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()