Extra row in QTableView

Perdrix

If I add three rows to my empty table model, the table view display the three rows I inserted, plus an extra blank row.

I'd much prefer not to have that!

If this isn't normal behaviour, what might cause this to happen?

Thanks
D

Perdrix

For my convenience, the FrameList class had this:

inline FrameList& beginInsertRows(int count) noexcept
{
	auto first{ imageGroups[index].pictures.rowCount() };	// Insert after end
	auto last{ first + count };
	imageGroups[index].pictures.beginInsertRows(QModelIndex(), first, last);
	return (*this);
}

which I now realise had an "off by one" error!

I changed the code to read:

auto last{ first + count -1};

and it now works as I would hope!!

I also changed addImage() to read:

void ImageListModel::addImage(ListBitMap image)
{
    Q_ASSERT(std::find(mydata.begin(), mydata.end(), image) == mydata.end());
            
    mydata.emplace_back(std::move(image));
}

as it should never actually attempt to add the same file twice (there are other checks).

Thanks for the help in tracking this down.

D.

JonB

@Perdrix
"Nothing" would make that happen. And what about when you have 0 rows in the table without inserting anything? Are you sure your "extra blank row" is not just the empty area at the bottom/right of a QTreeView depending on its size? Otherwise show screenshot and code.

Perdrix

Here's what the view looks like b4 loading a file:

and now after loading one file:

Here's the code that did it:

		if (QDialog::Accepted == fileDialog.exec())
		{
			QGuiApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
			QStringList files = fileDialog.selectedFiles();

			//
			// Before attempting to add the files prune out those that have already been loaded
			// and issue an error message
			//
			auto it = std::remove_if(files.begin(), files.end(), 
				[&](const QString& s) { return fileAlreadyLoaded(s.toStdU16String()); });
			files.erase(it, files.end());

			//
			// Now add the images to the end of the current group in the frame list remembering
			// that we need to bracket the code  that adds the with beginInsertRows(rowcount) and
			// endInsertRows(), so the table model is informed of the new rows
			//
			frameList.beginInsertRows(files.size());
			for (int i = 0; i < files.size(); i++)
			{
				fs::path file(files.at(i).toStdU16String());		// as UTF-16

				frameList.addFile(file);

				if (file.has_parent_path())
					directory = QString::fromStdU16String(file.parent_path().generic_u16string());
				else
					directory = QString::fromStdU16String(file.root_path().generic_u16string());

				extension = QString::fromStdU16String(file.extension().generic_u16string());
			}
			frameList.endInsertRows();

the addFile mf of FrameList class reads like:

		virtual bool addFile(fs::path file, PICTURETYPE PictureType = PICTURETYPE_LIGHTFRAME, bool bCheck = false, int nItem = -1)
		{
			imageGroups[index].addFile(file, PictureType, bCheck);
			return true;
		}

and the mf that calls looks like:

	void Group::addFile(fs::path file, PICTURETYPE PictureType, bool bCheck, [[maybe_unused]] int32_t nItem)
	{
		ZFUNCTRACE_RUNTIME();

		ListBitMap			lb;

		lb.m_groupId = Index;

		if (lb.InitFromFile(file, PictureType))
		{
                      : stuff deleted
		};

		pathToGroup.emplace(file, Index);

		pictures.addImage(lb);

pictures is an instance of a derived class of QAbstractTableModel which stores a std::vector<ListBitmap> as its backing data.

the addImage() mf looks like:

    //
    // Add an image (row) to the table, Before calling addImage, Qt requires that 
    // beginInsertRows() be called, and once batch of images is added, then
    // endInsertRows() must be called.
    //
    void ImageListModel::addImage(ListBitMap image)
    {
        if (std::find(mydata.begin(), mydata.end(), image) != mydata.end())
            return;
        mydata.emplace_back(std::move(image));
    }

the rowCount mf() is simply:

        int rowCount(const QModelIndex& parent = QModelIndex()) const override
        {
            // Return number of images we know about
            return static_cast<int>(mydata.size());
        };

I checked using the debugger and rowCount is returning 1 after adding one file as I would expect.

JonB

@Perdrix
I admit I cannot spot what the issue is. [* Now see UPDATE below.]

Remove all your code (for reading files, inserting into list/table, images, beginInsertRows(), etc.)! Just have rowCount() unconditionally return 1;. What does the table look like now? :)

You return mydata.size(). But mageListModel::addImage() does not append an item to mydata if the image is already "found" in the list. Is that relevant?

You have not said anything about your model, but I assume you are implementing your own QAbstractItemModel. Strange things happen if the implementation is incorrect. There is a QAbstractItemModelTester Class to test implementations, of ten it uncovers something.

UPDATE STOP!!
What is your

frameList.beginInsertRows(files.size());

?? How does this get through Python? https://doc.qt.io/qtforpython/PySide6/QtCore/QAbstractItemModel.html#PySide6.QtCore.PySide6.QtCore.QAbstractItemModel.beginInsertRows

PySide6.QtCore.QAbstractItemModel.beginInsertRows(parent, first, last)

PARAMETERS

parent – PySide6.QtCore.QModelIndex

first – int

last – int

So apart from wrong number of parameters, note that last would need to be mydata.size() - 1.... Looks like you are telling it you're inserting 1 more than you are, hence an extra blank row at end? :)

mchinand

The implementation of beginInsertRows() for frameList model sub-class must allow just the number of rows as a single parameter but apparently isn't calling the base class implementation correctly as @JonB points out.

Perdrix

@JonB said in Extra row in QTableView:

What is your
frameList.beginInsertRows(files.size())

it was 1 - I checked in the debugger.

What Python got to do with it?

David

Perdrix