You could set a variable for the duration of "loading" and release at the end instead. That variable could be tested in the slot(s) for itemChanged() only and do nothing while set. Just a thought.

Thanks for your kindly suggestion.

Actually, the reason I want to know the source of modification is :
There are 2 table views A and B in my case. When user edit Table A via UI, setting a check box checked, QStandardItemModel::itemChanged would be emitted and inform of Table B to add a corresponding row. It works as expected. BUT when opening a file to read data, Table A and Table B are loaded respectively and I find there are many duplicated rows in Table B. The root cause is that when loading Table A, signal QStandardItemModel::itemChanged is also triggered.

So I want to prevent that signal to add rows into Table B when load files. How can I use QStandardItem::setText() to solve this issue?

How can I tell which is the true trigger?

You can't since the model does not know it since QSIM::setData() is called without a hint from where the modifcation came from (which would be pointless somehow - an enum with all possible entry methods? Why?)

But since you call QStandardItem::setText() you know when the text is set programatically.