CopperSpice API  1.7.2
QDrag Class Reference

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

Inheritance diagram for QDrag:
QObject

Public Signals

void actionChanged (Qt::DropAction action)
 
void targetChanged (QObject *newTarget)
 
- Public Signals inherited from QObject
void destroyed (QObject *obj=nullptr)
 
void objectNameChanged (const QString &objectName)
 

Public Methods

 QDrag (QObject *dragSource)
 
 ~QDrag ()
 
Qt::DropAction defaultAction () const
 
QPixmap dragCursor (Qt::DropAction action) const
 
Qt::DropAction exec (Qt::DropActions supportedActions, Qt::DropAction defaultAction)
 
Qt::DropAction exec (Qt::DropActions supportedActions=Qt::MoveAction)
 
QPoint hotSpot () const
 
QMimeDatamimeData () const
 
QPixmap pixmap () const
 
void setDragCursor (const QPixmap &cursor, Qt::DropAction action)
 
void setHotSpot (const QPoint &hotspot)
 
void setMimeData (QMimeData *data)
 
void setPixmap (const QPixmap &pixmap)
 
QObjectsource () const
 
Qt::DropAction start (Qt::DropActions supportedActions=Qt::CopyAction)
 
Qt::DropActions supportedActions () const
 
QObjecttarget () const
 
- Public Methods inherited from QObject
 QObject (QObject *parent=nullptr)
 
 ~QObject ()
 
bool blockSignals (bool block)
 
const QList< QObject * > & children () const
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
void dumpObjectInfo ()
 
void dumpObjectTree ()
 
QList< QStringdynamicPropertyNames () const
 
virtual bool event (QEvent *event)
 
virtual bool eventFilter (QObject *watched, QEvent *event)
 
template<typename T >
findChild (const QString &childName=QString ()) const
 
template<class T >
QList< T > findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
template<class T >
QList< T > findChildren (const QString &objName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
bool inherits (const QString &className) const
 
void installEventFilter (QObject *filterObj)
 
bool isWidgetType () const
 
bool isWindowType () const
 
void killTimer (int id)
 
const QMetaObjectmetaObject () const
 
void moveToThread (QThread *targetThread)
 
QString objectName () const
 
QObject * parent () const
 
template<class T = QVariant>
property (const QString &name) const
 
void removeEventFilter (QObject *obj)
 
void setObjectName (const QString &name)
 
void setParent (QObject *parent)
 
bool setProperty (const QString &name, const QVariant &value)
 
bool signalsBlocked () const
 
int startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
 
QThreadthread () const
 

Additional Inherited Members

- Public Slots inherited from QObject
void deleteLater ()
 
- Static Public Methods inherited from QObject
static bool connect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool connect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())
 
static bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool disconnect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...))
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)
 
static QMetaObjectstaticMetaObject ()
 
static QString tr (const char *text, const char *comment=nullptr, std::optional< int > numArg=std::optional< int >())
 
- Protected Methods inherited from QObject
virtual void childEvent (QChildEvent *event)
 
virtual void connectNotify (const QMetaMethod &signalMethod) const
 
virtual void customEvent (QEvent *event)
 
virtual void disconnectNotify (const QMetaMethod &signalMethod) const
 
bool isSignalConnected (const QMetaMethod &signalMethod) const
 
int receivers (const QString &signal) const
 
QObject * sender () const
 
int senderSignalIndex () const
 
virtual void timerEvent (QTimerEvent *event)
 
- Properties inherited from QObject
 objectName
 

Detailed Description

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

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 CopperSpice 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:

QDrag *drag = new QDrag(this);
mimeData->setText(commentEdit->toPlainText());

Note that setMimeData() assigns ownership of the QMimeData object to the QDrag object. The QDrag must be constructed on the heap with a parent QWidget to ensure that CopperSpice 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()));

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, QWindowsMime, QMacPasteboardMime

Constructor & Destructor Documentation

QDrag::QDrag ( QObject dragSource)
explicit

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

QDrag::~QDrag ( )

Destroys the drag object.

Method Documentation

void QDrag::actionChanged ( Qt::DropAction  action)
signal

This signal is emitted when the action associated with the drag changes.

See also
targetChanged()
Qt::DropAction QDrag::defaultAction ( ) const

Returns the default proposed drop action for this drag operation.

See also
exec(), supportedActions()
QPixmap QDrag::dragCursor ( Qt::DropAction  action) const

Returns the drag cursor for the action.

Qt::DropAction QDrag::exec ( Qt::DropActions  supportedActions,
Qt::DropAction  defaultAction 
)

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

Note
On Linux and Mac OS X, 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 CopperSpice event loop is blocked during the operation. However, QDrag::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.
Qt::DropAction QDrag::exec ( Qt::DropActions  supportedActions = Qt::MoveAction)

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 Mac OS X, 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 CopperSpice event loop is blocked while during the operation.
QPoint QDrag::hotSpot ( ) const

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

See also
setHotSpot()
QMimeData * QDrag::mimeData ( ) const

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

See also
setMimeData()
QPixmap QDrag::pixmap ( ) const

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

See also
setPixmap()
void QDrag::setDragCursor ( const QPixmap cursor,
Qt::DropAction  action 
)

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.

The action can only be CopyAction, MoveAction or LinkAction. All other values of DropAction are ignored.

void QDrag::setHotSpot ( const QPoint hotspot)

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()
void QDrag::setMimeData ( QMimeData data)

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

See also
mimeData()
void QDrag::setPixmap ( const QPixmap pixmap)

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()
QObject * QDrag::source ( ) const

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

Qt::DropAction QDrag::start ( Qt::DropActions  supportedActions = Qt::CopyAction)
deprecated
Deprecated:
Note
It is recommended to use exec() instead of this method.

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. Qt::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()
Qt::DropActions QDrag::supportedActions ( ) const

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

See also
exec(), defaultAction()
QObject * QDrag::target ( ) const

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

void QDrag::targetChanged ( QObject newTarget)
signal

This signal is emitted when the target of the drag and drop operation changes, with newTarget the new target.

See also
target(), actionChanged()