Control Drag Operation

[sajis997]

Hello forum,

I am attaching an image where i have loaded a tree item into the tree view . Each of the item are draggable into the scene. But some of the tree items are not draggable based on their internal characteristics.

How can i do this ? I tried the following

if(node->getAbstract())
                setAcceptDrops(false);

if(node->getAbstract())
                setAcceptDrops(false);

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But i can drag the item which is supposed to be non-draggable.


Any hint?

Please Look at the attachment

Regards
Sajjad

[Spitfire]

Try

void    TreeWidget::mousePressEvent( QMouseEvent* e )
{
    this->draggedItem = item_you_will_drag;
    QTreeWidget::mousePressEvent( e );
}
 
void    TreeWidget::dragLeaveEvent( QDragLeaveEvent* e )
{
    if( this->draggedItem->getAbstract() )
    {
        e->setDropAction( Qt::IgnoreAction );
    }
    else
    {
        e->acceptProposedAction();
    }
 
    QTreeWidget::dragLeaveEvent( e );
}

void    TreeWidget::mousePressEvent( QMouseEvent* e )
{
    this->draggedItem = item_you_will_drag;
    QTreeWidget::mousePressEvent( e );
}

void    TreeWidget::dragLeaveEvent( QDragLeaveEvent* e )
{
    if( this->draggedItem->getAbstract() )
    {
        e->setDropAction( Qt::IgnoreAction );
    }
    else
    {
        e->acceptProposedAction();
    }

    QTreeWidget::dragLeaveEvent( e );
}

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This way the drop will be ignored on items that return true from getAbstract().

[sajis997]

Hi forum,


I did it in the dragEnterEvent instead. What is the basic difference between these dragLeaveEvent() and dragEnterEvent() these two ?

And it works fine the way i wanted, thanks for the hint .

void Editor::dragEnterEvent(QDragEnterEvent *event)
{
    if(event->mimeData()->hasText())
    {
        //get the node factory
        NodeFactory *l_nodeFactory;
        NodeData *l_node;
 
        if(Singleton<NodeFactory>::isInited())
        {
            //get the pointer for the factory
            l_nodeFactory = Singleton<NodeFactory>::getPtr();
 
            l_node = l_nodeFactory->getNodeData(event->mimeData()->text());
 
            if(!l_node->getAbstract())
            {
                event->setDropAction(Qt::CopyAction);
                event->accept();
            }
            else
            {
                event->setDropAction(Qt::IgnoreAction);
            }
        }
    }
    else
        event->ignore();
}

void Editor::dragEnterEvent(QDragEnterEvent *event)
{
    if(event->mimeData()->hasText())
    {
        //get the node factory
        NodeFactory *l_nodeFactory;
        NodeData *l_node;

        if(Singleton<NodeFactory>::isInited())
        {
            //get the pointer for the factory
            l_nodeFactory = Singleton<NodeFactory>::getPtr();

            l_node = l_nodeFactory->getNodeData(event->mimeData()->text());

            if(!l_node->getAbstract())
            {
                event->setDropAction(Qt::CopyAction);
                event->accept();
            }
            else
            {
                event->setDropAction(Qt::IgnoreAction);
            }
        }
    }
    else
        event->ignore();
}

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[Spitfire]

I don't know what your app is doing but if it's supposed to work with only internal structures, see what happens when you drag some text from other application onto it.

As to the difference - it's simple.
Drag enter handler is triggered when drag enter the widget, drag leave handler is triggered when drag leaves the widget.
Look up Drag and Drop in documentation for more details.