QDrag

The QDrag class provides support for MIME-based drag and drop data transfer. More

Inheritance diagram of PySide2.QtGui.QDrag

Synopsis

Functions

Signals

Static functions

Detailed Description

Drag and drop is an intuitive way for users to copy or move data around in an application, and is used in many desktop environments as a mechanism for copying data between applications. Drag and drop support in Qt is centered around the QDrag class that handles most of the details of a drag and drop operation.

The data to be transferred by the drag and drop operation is contained in a QMimeData object. This is specified with the setMimeData() function in the following way:

drag =  QDrag(self)
mimeData =  QMimeData()

mimeData.setText(commentEdit.toPlainText())
drag.setMimeData(mimeData)

Note that setMimeData() assigns ownership of the QMimeData object to the QDrag object. The QDrag must be constructed on the heap with a parent QObject to ensure that Qt can clean up after the drag and drop operation has been completed.

A pixmap can be used to represent the data while the drag is in progress, and will move with the cursor to the drop target. This pixmap typically shows an icon that represents the MIME type of the data being transferred, but any pixmap can be set with setPixmap() . The cursor’s hot spot can be given a position relative to the top-left corner of the pixmap with the setHotSpot() function. The following code positions the pixmap so that the cursor’s hot spot points to the center of its bottom edge:

drag->setHotSpot(QPoint(drag->pixmap().width()/2,
                        drag->pixmap().height()));

Note

On X11, the pixmap may not be able to keep up with the mouse movements if the hot spot causes the pixmap to be displayed directly under the cursor.

The source and target widgets can be found with source() and target() . These functions are often used to determine whether drag and drop operations started and finished at the same widget, so that special behavior can be implemented.

QDrag only deals with the drag and drop operation itself. It is up to the developer to decide when a drag operation begins, and how a QDrag object should be constructed and used. For a given widget, it is often necessary to reimplement mousePressEvent() to determine whether the user has pressed a mouse button, and reimplement mouseMoveEvent() to check whether a QDrag is required.

See also

Drag and Drop QClipboard QMimeData Draggable Icons Example Draggable Text Example Drop Site Example Fridge Magnets Example

class QDrag(dragSource)
param dragSource

QObject

Constructs a new drag object for the widget specified by dragSource .

PySide2.QtGui.QDrag.actionChanged(action)
Parameters

actionDropAction

static PySide2.QtGui.QDrag.cancel()

Cancels a drag operation initiated by Qt.

Note

This is currently implemented on Windows and X11.

See also

exec()

PySide2.QtGui.QDrag.defaultAction()
Return type

DropAction

Returns the default proposed drop action for this drag operation.

See also

exec() supportedActions()

PySide2.QtGui.QDrag.dragCursor(action)
Parameters

actionDropAction

Return type

QPixmap

Returns the drag cursor for the action .

See also

setDragCursor()

PySide2.QtGui.QDrag.exec_([supportedActions=Qt.MoveAction])
Parameters

supportedActionsDropActions

Return type

DropAction

Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in supportedActions . The default proposed action will be selected among the allowed actions in the following order: Move, Copy and Link.

Note

On Linux and macOS , the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked during the operation.

See also

cancel()

PySide2.QtGui.QDrag.exec_(supportedActions, defaultAction)
Parameters
  • supportedActionsDropActions

  • defaultActionDropAction

Return type

DropAction

Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in supportedActions .

The defaultDropAction determines which action will be proposed when the user performs a drag without using modifier keys.

Note

On Linux and macOS , the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked during the operation. However, exec() on Windows causes processEvents() to be called frequently to keep the GUI responsive. If any loops or operations are called while a drag operation is active, it will block the drag operation.

PySide2.QtGui.QDrag.hotSpot()
Return type

QPoint

Returns the position of the hot spot relative to the top-left corner of the cursor.

See also

setHotSpot()

PySide2.QtGui.QDrag.mimeData()
Return type

QMimeData

Returns the MIME data that is encapsulated by the drag object.

See also

setMimeData()

PySide2.QtGui.QDrag.pixmap()
Return type

QPixmap

Returns the pixmap used to represent the data in a drag and drop operation.

See also

setPixmap()

PySide2.QtGui.QDrag.setDragCursor(cursor, action)
Parameters
  • cursorQPixmap

  • actionDropAction

Sets the drag cursor for the action . This allows you to override the default native cursors. To revert to using the native cursor for action pass in a null QPixmap as cursor .

Note: setting the drag cursor for IgnoreAction may not work on all platforms. X11 and macOS has been tested to work. Windows does not support it.

See also

dragCursor()

PySide2.QtGui.QDrag.setHotSpot(hotspot)
Parameters

hotspotQPoint

Sets the position of the hot spot relative to the top-left corner of the pixmap used to the point specified by hotspot .

Note

on X11, the pixmap may not be able to keep up with the mouse movements if the hot spot causes the pixmap to be displayed directly under the cursor.

See also

hotSpot()

PySide2.QtGui.QDrag.setMimeData(data)
Parameters

dataQMimeData

Sets the data to be sent to the given MIME data . Ownership of the data is transferred to the QDrag object.

See also

mimeData()

PySide2.QtGui.QDrag.setPixmap(arg__1)
Parameters

arg__1QPixmap

Sets pixmap as the pixmap used to represent the data in a drag and drop operation. You can only set a pixmap before the drag is started.

See also

pixmap()

PySide2.QtGui.QDrag.source()
Return type

QObject

Returns the source of the drag object. This is the widget where the drag and drop operation originated.

PySide2.QtGui.QDrag.start([supportedActions=Qt.CopyAction])
Parameters

supportedActionsDropActions

Return type

DropAction

Note

This function is deprecated.

Note

It is recommended to use exec() instead of this function.

Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in request . CopyAction is always allowed.

Note

Although the drag and drop operation can take some time, this function does not block the event loop. Other events are still delivered to the application while the operation is performed.

See also

exec()

PySide2.QtGui.QDrag.supportedActions()
Return type

DropActions

Returns the set of possible drop actions for this drag operation.

See also

exec() defaultAction()

PySide2.QtGui.QDrag.target()
Return type

QObject

Returns the target of the drag and drop operation. This is the widget where the drag object was dropped.

PySide2.QtGui.QDrag.targetChanged(newTarget)
Parameters

newTargetQObject