Hi there again,
Just for the sake of clarity: The TreeItem class has one central idea, that is
to map the DataStorage's cyclic graph data structure into a tree structure. We
wanted to have a tree view for the DataManager because we thought it is more
user friendly than any view to navigate a graph and the use cases are rare in
which a DataNode needs to have more than one parent.
Anyway, this mapping could be also packed in a QStandardItemModel-derived class
and we are certainly interested.
For the upcoming release I will nevertheless merge the code that is necessary
to resolve the issue you reported in the previous mail below.
Best
Michael
Von: Rostislav Khlebnikov [mailto:rostislav.khlebni...@kcl.ac.uk]
Gesendet: Dienstag, 2. September 2014 17:08
An: Müller, Michael
Cc: mitk-users
Betreff: Re: [mitk-users] QSortFilterProxyModel bugfix and node deletion
performance
Additionally, seems a similar bug was reported in Qt quite a while ago, but no
action was taken because the bug reporter didn't provide enough information:
https://bugreports.qt-project.org/browse/QTBUG-27289
And also, while searching for the reason for crash, I made a test where I
basically replaced the base class for QmitkDataStorageTreeModel from
QAbstractItemModel to QStandardItemModel, thus removing the custom tree
hierarchy code (everything related to QmitkDataStorageTreeModel::TreeItem). I
don't really see any advantages in having this own tree hierarchy and I believe
that re-using Qt code will always be more robust and clean than having it
basically duplicated in MITK. Would you be interested in these changes?
Rostislav.
On 02/09/2014 14:36, Rostislav Khlebnikov wrote:
Hello Michael,
it seems as if there is a bug in my contribution (VERY obscure one - took me
several days to figure it out). Basically, when several nodes are deleted by
the user, selectionChanged() signal is emitted after the first of the nodes is
removed. This leads to setting the "selected" property on the other node that
is yet to be deleted. This eventually calls NodeChanged() of the data manager
view which calls invalidate() on the filter model. Turns out that this call
stack, that is filter invalidation during row deletion, screws up the
QSortFilterProxyModel's internal state and leads to a crash in a very obscure
place within Qt code.
Could you please check this for me? The reproduction steps are really simple.
Fire up an empty workbench instance, show hidden nodes and nodes with no data,
select widget3Plane and widget2Plane under Widgets, and delete them - this
leads to crash in my case.
If it does crash - then I found the following solution to work. To avoid
immediate filter invalidation, I postpone it using Qt::QueuedConnection slot
invocation. So if you replace the code of NodeChanged() in QmitkDataManagerView
from
m_FilterModel->invalidate();
to
QMetaObject::invokeMethod(m_FilterModel, "invalidate",
Qt::QueuedConnection);
then the crash willl be fixed.
Also during my struggles in searching for the causes of this crash, I have
found that in QmitkDataManagerView::RemoveSelectedNodes,
this->GlobalReinit(false) is called after every node is deleted. I doubt it
makes any sense, so I believe it should be moved out of the loop over the nodes
being deleted, so that GlobalReinit() is called only once all selected nodes
are removed. This should increase the performance.
Rostislav.
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