expanding tree view problem

[joeld42]

I've got a custom tree model/view. I've got a slot on the treeView called expandNonDefaultNodes(), which goes through all the nodes, and calls setExpanded( index, true ) on every node that isn't at the default value.

This behaves correctly, except I get a bunch of these warnings on the shell:

QPainter::begin: Cannot paint on a null pixmap
QPainter::translate: Painter not active
QPainter::end: Painter not active, aborted

QPainter::begin: Cannot paint on a null pixmap
QPainter::translate: Painter not active
QPainter::end: Painter not active, aborted

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The debugger indicates that this is coming from the scrollbars.

However, if I call QTreeView's expandAll() instead, it works. What is QTreeView::expandAll() doing that I'm not? I looked at the code for expandAll(), and there's some stuff I don't understand (like d->layout(-1) ) but I am calling update(), updateGeometries() and viewport()->update().

[wysota]

Can we see your code?

[joeld42]

Sure, here's the whole function:

void JasperView::expandNonDefaultNodes()
{
    // If I uncomment this, I don't get the QPainter warnings
    // and ALL the nodes are expanded..
    //expandAll();
    //return;
 
    QAbstractItemModel *mdl = model();
    QModelIndex rootNdx = rootIndex();
 
    for (int i=0; i < mdl->rowCount( rootNdx ); ++i)
    {
        QModelIndex ctrIndex = mdl->index( i, 0, rootNdx );
        BlockTreeItem *item = getItem( ctrIndex );
 
        // For binds, just expand so the fcalls are visible (for now)
        BindBlockItem *bindBlock = dynamic_cast<BindBlockItem*>( item );
        if (bindBlock)
        {
            setExpanded( ctrIndex, true );
        }
 
        // For functions, expand out any nodes with non-default values
        FuncBlockItem *funcBlock = dynamic_cast<FuncBlockItem*>( item );
 
        if (funcBlock)
        {
            bool anyExpandedNodes = false;
            for (int j=0; j < mdl->rowCount( ctrIndex ); ++j )
            {
                QModelIndex nodeIndex = mdl->index( j, 0, ctrIndex );
                ParamNodeItem *nodeItem = dynamic_cast<ParamNodeItem*>( getItem( nodeIndex ) );
                ParamNode *node = nodeItem->block();
 
                if (node)
                {
                    bool shouldExpand = node->anyChangesFromDefault();
                    setExpanded( nodeIndex, shouldExpand );
 
                    anyExpandedNodes = anyExpandedNodes | shouldExpand;
                }
            }
 
            // Expand this container if any of it's nodes
            // are expanded
            setExpanded( ctrIndex, anyExpandedNodes );
 
        }
    }
 
    // these don't seem to make any difference
    updateGeometries();
    viewport()->update();
    update();
}

void JasperView::expandNonDefaultNodes()
{
    // If I uncomment this, I don't get the QPainter warnings
    // and ALL the nodes are expanded..
    //expandAll();
    //return;

    QAbstractItemModel *mdl = model();
    QModelIndex rootNdx = rootIndex();

    for (int i=0; i < mdl->rowCount( rootNdx ); ++i)
    {
        QModelIndex ctrIndex = mdl->index( i, 0, rootNdx );
        BlockTreeItem *item = getItem( ctrIndex );

        // For binds, just expand so the fcalls are visible (for now)
        BindBlockItem *bindBlock = dynamic_cast<BindBlockItem*>( item );
        if (bindBlock)
        {
            setExpanded( ctrIndex, true );
        }

        // For functions, expand out any nodes with non-default values
        FuncBlockItem *funcBlock = dynamic_cast<FuncBlockItem*>( item );

        if (funcBlock)
        {
            bool anyExpandedNodes = false;
            for (int j=0; j < mdl->rowCount( ctrIndex ); ++j )
            {
                QModelIndex nodeIndex = mdl->index( j, 0, ctrIndex );
                ParamNodeItem *nodeItem = dynamic_cast<ParamNodeItem*>( getItem( nodeIndex ) );
                ParamNode *node = nodeItem->block();

                if (node)
                {
                    bool shouldExpand = node->anyChangesFromDefault();
                    setExpanded( nodeIndex, shouldExpand );

                    anyExpandedNodes = anyExpandedNodes | shouldExpand;
                }
            }

            // Expand this container if any of it's nodes
            // are expanded
            setExpanded( ctrIndex, anyExpandedNodes );

        }
    }

    // these don't seem to make any difference
    updateGeometries();
    viewport()->update();
    update();
}

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I've tried replacing the setExpanded() calls with expand() but it does the same thing. I have verified that the setExpandeds actually get called.

One other little detail, I was calling this from my openFile, after I loaded the model data and did a setModel. That resulted in nothing expanding (again, expandAll works). I'm now calling it with this:

QTimer::singleShot( 0, ui.treeView, SLOT(expandNonDefaultNodes()) );

QTimer::singleShot( 0, ui.treeView, SLOT(expandNonDefaultNodes()) );

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And it works, but i get the warnings. Same thing if I call it from a QAction.

this is qt 4.5.0, btw.

[wysota]

What happens if you increase the timeout of the timer to 100ms or so?

[joeld42]

Ok, so I figured it out. I had the "animated" property set, and that was causing problems. I wrapped the function with setAnimated( false ), setAnimated( true) and it works now.

In the process of figuring this out, I modified simpletreeview to exhibit the same behavior, attached if anyone's curious. I'm not sure how to file a bug report, and in any case, I've got a good workaround.

Thanks!
Joel