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.

What Python got to do with it?

Absolutely nothing :) I suddenly thought you had been writing in Python, and were somehow getting away with passing too few parameters, upon looking now I have no idea why!

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.

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

it was 1 - I checked in the debugger.

What Python got to do with it?

David

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? :)

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.