[Python] PyQt 6.9: Implementing row movement via drag and drop on a QTableView with hidden...

I'm working on an application that uses a QTableView and have been trying to get it to respond correctly to dragging and dropping rows in order to rearrange them. After a lot of difficulty, I found this comment on a post that was describing the exact problems that I was having with rows "disappearing" when dropped. The comment suggested a more intuitive method would be available in Qt 6.9, and I recalled that PyQt 6.9 was recently released.

I updated my version of the library and tested out an implementation in a minimal example (below). I saw that it worked great for the two requirements I needed:

1. 
   A user can only drop rows between existing rows, before the first row, or after the last row. There's no way to overwrite a row by dropping a row on top of it.
   
   
2. 
   The row should be inserted at column 0 all the time, to avoid the dropped row being offset and ending up adding columns to the model/view.
   

However, when I went to implement in my full application, it stopped working as intended. I narrowed the issue down to the fact that my application hides column 0. When this happens, there's two impacts:

1. 
   The dropIndicator in the table stops appearing correctly between rows.
   
   
2. 
   Dropping a row between other rows causes the data in column 0 for the moved row to be lost, and all remaining columns' data decrement their positions in the row.
   

I think I can work around this; I was hiding column 0 because at the time I wrote the code I didn't want the data in the column to be visible in the table. I've since learned that I can place additional data in an index under another role, so I think I can do that instead and not hide any columns.

However, I'd love to know more about why hiding the column breaks the intended functionality if anyone knows why. Uncommenting line 21 in the code should illustrate what I am seeing.

import sys

from PyQt6.QtCore import Qt
from PyQt6.QtGui import QStandardItemModel, QStandardItem
from PyQt6.QtWidgets import (QApplication, QMainWindow, QTableView, QAbstractItemView, QWidget, QVBoxLayout, QPushButton)


class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.central_widget = QWidget()
self.setCentralWidget(self.central_widget)
self.central_widget.setLayout(QVBoxLayout())
self.table = QTableView()
self.central_widget.layout().addWidget(self.table)
self._config_table()
self.model = self._make_model()
self.table.setModel(self.model)
self.table.resizeRowsToContents()
self.table.resizeColumnsToContents()
#self.table.hideColumn(0)
self.button = QPushButton("Check")
self.central_widget.layout().addWidget(self.button)
self.button.clicked.connect(self._log_model_contents)
self.show()

def _config_table(self):
self.table.setDragDropMode(QAbstractItemView.DragDropMode.InternalMove)
self.table.setSelectionBehavior(QAbstractItemView.SelectionBehavior.SelectRows)
self.table.setDragEnabled(True)
self.table.setAcceptDrops(True)
self.table.setDropIndicatorShown(True)
self.table.setDragDropOverwriteMode(False)

def _make_model(self):
data = [
[1, 2, 3, 4, 5],
["a", "b", "c", "d", "e"],
[5.2, 5.3, 5.4, 5.5, 5.6],
[0, 0, None, 0, 9999]
]
model = MyModel(0, 5)
for r in data:
items_row = list(map(lambda x: QStandardItem(str(x) if x is not None else None), r))
for item in items_row:
item.setFlags(Qt.ItemFlag.ItemIsSelectable | Qt.ItemFlag.ItemIsEnabled | Qt.ItemFlag.ItemIsSelectable | Qt.ItemFlag.ItemIsDragEnabled |
Qt.ItemFlag.ItemIsEditable)
model.appendRow(items_row)
return model

def _log_model_contents(self):
for r in range(0, self.model.rowCount()):
row_data = []
for c in range(0, self.model.columnCount()):
row_data.append(self.model.index(r, c).data(Qt.ItemDataRole.DisplayRole))
print(r, row_data)


class MyModel(QStandardItemModel):

def dropMimeData(self, data, action, row, column, parent):
return super().dropMimeData(data, action, row, 0, parent)


app = QApplication([])
my_window = MainWindow()
sys.exit(app.exec())

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