C++ QDragManager类代码示例

Qt::DropAction QDrag::exec(Qt::DropActions supportedActions, Qt::DropAction defaultDropAction)
{
    Q_D(QDrag);
    if (!d->data) {
        qWarning("QDrag: No mimedata set before starting the drag");
        return d->executed_action;
    }
    QDragManager *manager = QDragManager::self();
    d->defaultDropAction = Qt::IgnoreAction;
    d->possible_actions = supportedActions;

    if (manager) {
        if (defaultDropAction == Qt::IgnoreAction) {
            if (supportedActions & Qt::MoveAction) {
                d->defaultDropAction = Qt::MoveAction;
            } else if (supportedActions & Qt::CopyAction) {
                d->defaultDropAction = Qt::CopyAction;
            } else if (supportedActions & Qt::LinkAction) {
                d->defaultDropAction = Qt::LinkAction;
            }
        } else {
            d->defaultDropAction = defaultDropAction;
        }
        d->executed_action = manager->drag(this);
    }

    return d->executed_action;
}

/*!
    \obsolete

    \bold{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 \a request. Qt::CopyAction is always allowed.

    \bold{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.

    \sa exec()
*/
Qt::DropAction QDrag::start(Qt::DropActions request)
{
    Q_D(QDrag);
    if (!d->data) {
        qWarning("QDrag: No mimedata set before starting the drag");
        return d->executed_action;
    }
    QDragManager *manager = QDragManager::self();
    d->defaultDropAction = Qt::IgnoreAction;
    d->possible_actions = request | Qt::CopyAction;
    if (manager)
        d->executed_action = manager->drag(this);
    return d->executed_action;
}

bool QDragManager::eventFilter(QObject *o, QEvent *e)
{
    if (beingCancelled) {
        if (e->type() == QEvent::KeyRelease && static_cast<QKeyEvent*>(e)->key() == Qt::Key_Escape) {
            qApp->removeEventFilter(this);
            Q_ASSERT(object == 0);
            beingCancelled = false;
#ifndef QT_NO_LOCALEVENTLOOP
            eventLoop->exit();
#else
            asyncDragFinished();
#endif
            return true; // block the key release
        }
        return false;
    }



    if (!o->isWidgetType())
        return false;

    switch(e->type()) {
    case QEvent::ShortcutOverride:
        // prevent accelerators from firing while dragging
        e->accept();
        return true;

    case QEvent::KeyPress:
    case QEvent::KeyRelease:
    {
        QKeyEvent *ke = ((QKeyEvent*)e);
        if (ke->key() == Qt::Key_Escape && e->type() == QEvent::KeyPress) {
            cancel();
            qApp->removeEventFilter(this);
            beingCancelled = false;
#ifndef QT_NO_LOCALEVENTLOOP
            eventLoop->exit();
#else
            asyncDragFinished();
#endif
        } else {
            updateCursor();
        }
        return true; // Eat all key events
    }

    case QEvent::MouseButtonPress:
    case QEvent::MouseMove:
    {
        if (!object) { //#### this should not happen
            qWarning("QDragManager::eventFilter: No object");
            return true;
        }

        QDragManager *manager = QDragManager::self();
        QMimeData *dropData = manager->object ? manager->dragPrivate()->data : manager->dropData;
        if (manager->object)
            possible_actions =  manager->dragPrivate()->possible_actions;
        else
            possible_actions = Qt::IgnoreAction;

        QMouseEvent *me = (QMouseEvent *)e;
        if (me->buttons()) {
            Qt::DropAction prevAction = global_accepted_action;
            QWidget *cw = QApplication::widgetAt(me->globalPos());

            // Fix for when we move mouse on to the deco widget
            if (qt_qws_dnd_deco && cw == qt_qws_dnd_deco)
                cw = object->target();

            while (cw && !cw->acceptDrops() && !cw->isWindow())
                cw = cw->parentWidget();

            if (object->target() != cw) {
                if (object->target()) {
                    QDragLeaveEvent dle;
                    QApplication::sendEvent(object->target(), &dle);
                    willDrop = false;
                    global_accepted_action = Qt::IgnoreAction;
                    updateCursor();
                    restoreCursor = true;
                    object->d_func()->target = 0;
                }
                if (cw && cw->acceptDrops()) {
                    object->d_func()->target = cw;
                    QDragEnterEvent dee(cw->mapFromGlobal(me->globalPos()), possible_actions, dropData,
                                        me->buttons(), me->modifiers());
                    QApplication::sendEvent(object->target(), &dee);
                    willDrop = dee.isAccepted() && dee.dropAction() != Qt::IgnoreAction;
                    global_accepted_action = willDrop ? dee.dropAction() : Qt::IgnoreAction;
                    updateCursor();
                    restoreCursor = true;
                }
            } else if (cw) {
                QDragMoveEvent dme(cw->mapFromGlobal(me->globalPos()), possible_actions, dropData,
                                   me->buttons(), me->modifiers());
                if (global_accepted_action != Qt::IgnoreAction) {
                    dme.setDropAction(global_accepted_action);
                    dme.accept();
//.........这里部分代码省略.........

bool QDragManager::eventFilter(QObject *o, QEvent *e)
{
 if (beingCancelled) {
        return false;
    }
    if (!o->isWidgetType())
        return false;

    switch(e->type()) {
        case QEvent::MouseButtonPress:
        {
        }
        case QEvent::MouseMove:
        {
            if (!object) { //#### this should not happen
                qWarning("QDragManager::eventFilter: No object");
                return true;
            }
            QDragManager *manager = QDragManager::self();
            QMimeData *dropData = manager->object ? manager->dragPrivate()->data : manager->dropData;
            if (manager->object)
                possible_actions =  manager->dragPrivate()->possible_actions;
            else
                possible_actions = Qt::IgnoreAction;

            QMouseEvent *me = (QMouseEvent *)e;

            if (me->buttons()) {
                Qt::DropAction prevAction = global_accepted_action;
                QWidget *cw = QApplication::widgetAt(me->globalPos());
                // map the Coords relative to the window.
                if (!cw)
                    return true;

                while (cw && !cw->acceptDrops() && !cw->isWindow())
                    cw = cw->parentWidget();

                bool oldWillDrop = willDrop;
                if (object->target() != cw) {
                    if (object->target()) {
                        QDragLeaveEvent dle;
                        QApplication::sendEvent(object->target(), &dle);
                        willDrop = false;
                        global_accepted_action = Qt::IgnoreAction;
                        if (oldWillDrop != willDrop)
                            updateCursor();
                        object->d_func()->target = 0;
                    }
                    if (cw && cw->acceptDrops()) {
                        object->d_func()->target = cw;
                        QDragEnterEvent dee(cw->mapFromGlobal(me->globalPos()), possible_actions, dropData,
                                            me->buttons(), me->modifiers());
                        QApplication::sendEvent(object->target(), &dee);
                        willDrop = dee.isAccepted() && dee.dropAction() != Qt::IgnoreAction;
                        global_accepted_action = willDrop ? dee.dropAction() : Qt::IgnoreAction;
                        if (oldWillDrop != willDrop)
                            updateCursor();
                    }
                } else if (cw) {
                    QDragMoveEvent dme(cw->mapFromGlobal(me->globalPos()), possible_actions, dropData,
                                       me->buttons(), me->modifiers());
                    if (global_accepted_action != Qt::IgnoreAction) {
                        dme.setDropAction(global_accepted_action);
                        dme.accept();
                    }
                    QApplication::sendEvent(cw, &dme);
                    willDrop = dme.isAccepted();
                    global_accepted_action = willDrop ? dme.dropAction() : Qt::IgnoreAction;
                    if (oldWillDrop != willDrop) {
                        updatePixmap();
                        updateCursor();
                    }
                }
                if (global_accepted_action != prevAction)
                    emitActionChanged(global_accepted_action);
            }
            return true; // Eat all mouse events
        }

        case QEvent::MouseButtonRelease:
        {
            qApp->removeEventFilter(this);
#ifndef QT_NO_CURSOR
            if (restoreCursor) {
                QApplication::restoreOverrideCursor();
                willDrop = false;
                restoreCursor = false;
            }
#endif
            if (object && object->target()) {

                QMouseEvent *me = (QMouseEvent *)e;

                QDragManager *manager = QDragManager::self();
                QMimeData *dropData = manager->object ? manager->dragPrivate()->data : manager->dropData;

                QDropEvent de(object->target()->mapFromGlobal(me->globalPos()), possible_actions, dropData,
                              me->buttons(), me->modifiers());
                QApplication::sendEvent(object->target(), &de);
                if (de.isAccepted())
//.........这里部分代码省略.........