@JonB @SGaist @DerReisende Thank you all very much. Thats kinda tedious to do but guess thats how it is. Appreciate all your help and indeed mapFrom and mapToSource are what fixes my issue. :D Y'all have a nice day.

@jaivardhanf said in How to change QTableView data based on selection in QComboBox.:

So below is my code.

Something seems to have gone wrong with the code tags, making it hard to read and potentially missing code.

Qt::ItemFlags LineModel::flags(const QModelIndex& index) const
{
return Qt::ItemIsEditable | QAbstractTableModel::flags(index);
}

Adding the ItemIsEditable flag doesn't matter if the goal isn't to edit the item through the view.

This is how I connect the signal and slot

connect(ui->lineClass, &QComboBox::currentTextChanged, this, &GetOptionsClass::TextChanged);

Verify that the slot is called when it should be, and that the arguments are as expected.

I found out the hard way that for large selections using the QItemSelectionModel::Rows option is a massive performance killer. The algorithm for extending the selection doesn't seem to be very good.
I had a case where manually creating QItemSelection with items for all columns and then selecting it in one call without that flag gave me even 30x boost. Give it a try.

@Dariusz I'm a nob. I captured selection range after action and not before. Storing selection before calling QTreeView::mouseReleaseEvent(event); seems to have solved the issue.