QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- )

[Dariusz]

Hey

This is been bothering me for a long time. I'm having an issue with drag/drop operation I've implemented on my models to properly emit signals. I keep getting "random" crashes here and there & debug is a bit dodgy... Here are the screen of debug errors :

Stack:

Pic of Error content

A code that I currently have... I'm not using beginMoveRows as I'm not sorting my items per parent in to proper groups... so just calling begin remove/beginInsert...

Here is the code of functions :

void myCustomItems::appendChildren(QVector<myCustomItems *> &items, bool notifyModel) {
    if (items.isEmpty())return;
    for (auto &item:items) {
        item->setParent(this);
    }
    if (notifyModel && mGenericModel) {
        mGenericModel->beginInsertRows(index(), mChildren.size(), mChildren.size() + items.size() - 1);
        mChildren.append(items);
        mGenericModel->endInsertRows();
    } else {
        mChildren.append(items);
    }
}

void myCustomItems::setParent(myCustomItems *myCustomItems) {
    if (mParent) {
        mParent->removeChild(this);
    }
    mParent = parent;
}

void myCustomItems::removeChild(myCustomItems *myCustomItems) {
    if (mGenericModel) {
        int k = mChildren.indexOf(nodePtr);
        mGenericModel->beginRemoveRows(index(), k, k);
        nodePtr->mParent = nullptr;
        mChildren.remove(k);
        mGenericModel->endRemoveRows();
    } else {
        mChildren.removeOne(nodePtr);
    }
}

void myCustomItems::insertChildren(QVector<myCustomItems *> items, int inx) {
    myCustomItems  *item=nullptr;
    if(inx<mChildren.size()){
            item = mChildren[inx];
    }
    for (auto &child:items) {
        child->setParent(this);
    }
    auto newInx = item->row();
    if(newInx==-1)inx=mChildren.size();
    else inx = newInx;
    if (inx > mChildren.size()) {
        mGenericModel->beginInsertRows(index(), mChildren.size(), mChildren.size() + items.size() - 1);
        mChildren.append(items);
        mGenericModel->endInsertRows();
    } else {
        if (inx > 0) { ///I sense I messed up this in a "way"...
            int offset = inx - 1;
            auto itm = mChildren[offset];
            while (items.contains(itm)) {
                --offset;
                if (offset == -1) {
                    break;
                }
                itm = mChildren[offset];
            }
            inx = mChildren.indexOf(itm) + 1;
        }
        if (mGenericModel)
            mGenericModel->beginInsertRows(index(), inx, inx + items.size() - 1);
        for (int x = 0; x < items.size(); ++x) {
            mChildren.insert(inx, items[x]);
        }
        if (mGenericModel)
            mGenericModel->endInsertRows();
    }
}

A gif of drag/drop operation... - if I reset QSortFilterProxy it resets the "dummy" entries...

How do I bite it ? I'm lost :- (

[Dariusz]

After getting full debug out of modelTest class I noticed an inconsistent output of row changes...
Did some digging and the issue ended up being...

AbstractModel & Identity lived in threadB
ProxySort lived in threadA.

And connection between them ended up being queuedconnection via qt auto connection system. Which meant that... the sort was getting notification incorrectly...

So lesson to learn.. "watch ur threads and what objects gets made where...".

Problem solved, for now :- )

TIA!

[Christian Ehrlicher]

What is testModel ? a QAbstractItemModel? If so you have to call begin/endInsertRow on that model, not on something other.

[Dariusz]

@Christian-Ehrlicher Yes testModel = QAbstractItemModel, everything happens on model level, nothing get happen on proxy/filter level.

The list of items are list of items not modelIndexes so index() would return index of the base abstract model and not filter/other one...

My head is going to explode, I cant see the error in this :- (( the simple append to group drag action that I perform is as simple as it gets. add/remove parents all it does. What do I dooo :- (

[Christian Ehrlicher]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Yes testModel = QAbstractItemModel,

So why do you call mGenericModel->beginInsertRows() then? You don't insert rows in mGenericModel at all...

[Dariusz]

@Christian-Ehrlicher said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Yes testModel = QAbstractItemModel,

So why do you call mGenericModel->beginInsertRows() then? You don't insert rows in mGenericModel at all...

eeee

class myCustomItems{
    testModel *mGenericModel
public:
      myCustomItems(const QString &displayString);
     ~myCustomItems();
     inline void setModel(testModel*modelPtr){mGenericModel=modelPtr};
}
 

I'm calling model signal from item to trigger the function thini... Or what should I do ? o.O

edit Fudge I messed up class name... sigh. corrected 1st post. My bad :- ( was trying to simplify the code from clutter

[Dariusz]

@Christian-Ehrlicher Ok so hours latter... I added layoutAboutToBeChanged() and layoutChanged() and changePersistentIndexList(indexBefore, indexAfter);

I noticed that I was getting now a weird qt warning...

		WARNING: QObject::connect: Cannot queue arguments of type 'QList<QPersistentModelIndex>'

(Make sure 'QList<QPersistentModelIndex>' is registered using qRegisterMetaType().)

I tried registering them via >

qRegisterMetaType<QList<QPersistentModelIndex>>("QList<QPersistentModelIndex>");
qRegisterMetaTypeStreamOperators<QList<QPersistentModelIndex>>("QList<QPersistentModelIndex>");

But I get error C2679: binary '>>': no operator found which takes a right-hand operand of type 'T' (or there is no acceptable conversion) I tried without const, same error. This happens when layoutChanged gets called... feels to me like that is the problem as sortModels/identityProxy needs to refresh properly...

What do I do now? :- (

Edit as a work around I ended up emiting myLayoutChanged() from my abstractModel to identityProxy to sortFilter which triggers invalidate() on sortFilter that "fixed" the issue. But as far as I'm conserned its a bug in Qt that the layoutAboutToBeChanged and layoutChanged does not work :- (

I'm on 5.14 version.

Any help would be amazing.

[Christian Ehrlicher]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Any help would be amazing.

Provide a minimal compilable example instead just some code fragments.

[VRonin]

Try spawning a Model Test side by side your model. Most of the time the error is easily caught by the test and it gives you a very good clue on what's going wrong

[Dariusz]

@VRonin said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Try spawning a Model Test side by side your model. Most of the time the error is easily caught by the test and it gives you a very good clue on what's going wrong

Wow, that's amazing! Thanks so much!

I've been testing my model for few days now, but I struggle with one error...

WARNING: FAIL! Compared values are not the same:
   Actual (model->rowCount(parent)) 4
   Expected (c.oldSize + (end - start + 1)) 5
   (qabstractitemmodeltester.cpp:669)

This happens during append function as far sa I can tell. I have 2 of them.

1st : - for appending vector of items

        mGenericModel->beginInsertRows(index(), mChildren.size(), mChildren.size() + items.size() - 1);
        mChildren.append(items);
        mGenericModel->endInsertRows();

2nd : - for appending 1 item.

        int loc = mChildren.size();
        mGenericModel->beginInsertRows(index(), loc, loc);
        mChildren.append(nodePtr);
        mGenericModel->endInsertRows();

The model->rowCount(parent) runs this:

{
    icGenericTreeItem *parentNode = getItemFromIndex(parent);
    if (!parentNode)return 0;
    return parentNode->getChildCount();
}

Does any of the code above look wrong?

[Dariusz]

Another error that I'm getting reports off is :

WARNING: QObject::connect: Cannot queue arguments of type 'QAbstractItemModel::LayoutChangeHint'
(Make sure 'QAbstractItemModel::LayoutChangeHint' is registered using qRegisterMetaType().)

No idea how to bite this one at all...

I sweat I'm not sending some signals/info to my proxy models. But I have no idea which/where. The TestModesl does not report anything in this case.

---

Here is my code for drag/drop action to handle indexes/layouts...

 Q_EMIT layoutAboutToBeChanged();

    QModelIndexList indexBefore;
    QModelIndexList indexAfter;
    std::reverse(newData.begin(), newData.end());

    /// Get old indexes
    for (int x = 0; x < newData.size(); ++x) {
        indexBefore.append(newData[x]->index());
    }

    /// Action below will emit beginRemoveRow for each item 1 by 1 and then beginInsertRows for each item 1 by 1. 1st remove all 
        rows then insert all rows.
    if (row == -1) {
        i->appendChildren(newData);
    } else {
        i->insertChildren(newData, row);
    }
    /// get new indexes
    for (int x = 0; x < newData.size(); ++x) {
        indexAfter.append(newData[x]->index());
    }

    changePersistentIndexList(indexBefore, indexAfter);
    Q_EMIT layoutChanged();

I mean the question that I have now... when I'm adding 20 items from random selection order. Can I 1st remove them all 1 by 1 and then add them in all in 1 call?

So assuming vector<treeItem*> items;
        for (auto &item:items) {
            item->setParent(this); // this calls removeRows(item->parent.index(),item->row(),item->row()); and endRemoveRows(); + item->parent.mChildren().removeItem(item->row());
            item->setModel(mGenericModel);
        }
and then:
        mGenericModel->beginInsertRows(index(), mChildren.size(), mChildren.size() + items.size() - 1);
        mChildren.append(items);
        mGenericModel->endInsertRows();

Or I cant call removeRows in this order and I have to removeRow then insert then remove then insert and so on ?
TIA

[kshegunov]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Another error that I'm getting reports off is :
WARNING: QObject::connect: Cannot queue arguments of type 'QAbstractItemModel::LayoutChangeHint'
(Make sure 'QAbstractItemModel::LayoutChangeHint' is registered using qRegisterMetaType().)

Please tell me you are not using threads ...

[Dariusz]

@kshegunov I've checked code, mostly nope except for selectionModel()->select(items); on my treeView.
Update() is called on QMetaInvole() via QueuedConnection.

Could the selection model cause it ? :O

[JKSH]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

mostly nope except for...

It needs to be 100% nope. Models and views are not thread-safe. They can crash if you run read/write their data from other threads.

It is possible to create thread-safe models, but you need to explicitly write your model code in a way that is thread safe.

[kshegunov]

What @JKSH said - no threading in the views & models.

[Dariusz]

So all of the issues I'm getting above could be due to running selection function on thread? :O Gotta test it now ! Brb.

[kshegunov]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

So all of the issues I'm getting above could be due to running selection function on thread?

And this is surprising? I've had a program run over a year before it hit a race condition, and I'd like to think I know what I'm doing.

[Christian Ehrlicher]

@Dariusz said in QSortFilterProxy & QIdentityProxyModel & QAbstractItemModel = Crash :- ):

Could the selection model cause it

It does, not could...

[Dariusz]

Hey

Ok so I disabled my threaded selection function but sadly I'm still getting crashes after large drag, dragging few items does not cause issue, but items with children/etc seems to cause crash more often. Its very random :- ((

[Christian Ehrlicher]

This still looks like a threading issue since _q_sourceRowsInserted() is the slot which is connected to the signal rowsInserted() from the source model. When both classes would be in the same thread then this function would have been called directly and not through an event like in your case here.

[Dariusz]

@Christian-Ehrlicher :O !

I have now
QAbstractItemModel = my model
QIdentityProxyModel = my custom identity - no changes here just place holder
QSortFilterProxyModel = this one is tweaked.

When I setModels on each of them, do I have to make any connections between them signals/slots of any of it?
I made one for selection/drag notifaction to re-select dropped items, but that is via QueuedConnection thus should not make any issue ?

I did more testing, seems like now any drag/drop is broken for me. Jezus... what a weekend.

I'm dropping QT from 5.14.0 to 5.13.1, perhaps its library bug as I'm running out of ideas whats wrong now :- (((