How often does QTableView update cells?

The answer to the title question is, more often than you thought, probably. Here's how I found out.

So a PGDP thing is the "good-words" file. During the multi-stage proofing process, the proofers can nominate words that fail the online spellcheck for the good-words list, meaning they are correct. Proper nouns, technical terms, archaisms, etc. It's a familiar concept in spell-checking, sometimes called a local dictionary.

A book downloaded by a post-processor usually has a good-words.txt file. When PPQT opens a book for the first time (there's no metadata file to be found), it looks for the good-words file, reads it, and makes sure that every word in it gets a free pass around the spellchecker. The good-words list gets written into the metadata file for later.

A feature of the words (vocabulary) panel is that you can select a word or words and have them added to the good-words list. In V1, this was done via a context menu command. You selected a word or words and right-clicked, and selected "Add to good words" from the popup menu. Then you had to confirm you wanted to do this to an OK/Cancel dialog, because there was no way to undo this step.

It was somewhat tedious. Clearing out all the misspellings is a major task during post-processing. There are often a hundred or more, very few of them actual misspellings. Verifying that they are not, and adding them to good-words, can take a while. So for V2 I was determined there would be a simpler drag-and-drop interface for this. I am showing the actual good-words list as a one-column table alongside the vocabulary table, and the user can just drag a word (or words, complex selections are allowed) into good-words.

When this is done, the "X" in the vocabulary window should immediately disappear, indicate removal of the misspelled status. Here's a short video of how it looks currently.

The play-by-play is: the word LOWENHEIM is marked as misspelled (the X in the Features column). The user drags it to the Good Words list. Immediately the X should go away, but it doesn't. Why not? Because I have not added any code to tell the Words Table View it needs to update that word. I meant to, but hadn't got around to it. However, the instant the words table is scrolled—you can tell there's a scroll happening because OS X displays the scrollbar temporarily—the X does disappear. Why?

Then, the user clicks on LOWENHEIM in the good words list and hits the Delete key. It is deleted from the list. Immediately the X should reappear in the Words table, but again, I haven't yet added code to signal a change from the list widget to the table widget. But again, upon the tiniest scroll movement, the X does reappear. Is it magic?

I conclude that whenever there is even a tiny bit of scrolling, the QTableView calls the data() method of the table model for fresh data. It wouldn't know to do that for the LOWENHEIM row in particular, so it must be doing it for every visible cell! The call to data() fetches the latest info about the word, including its new status as correctly, or incorrectly, spelled.

I had not anticipated this. I had supposed that the X's would not change until the user clicked the Refresh button, causing a table model reset. This would not be a nice UI, so I had expected I would need to add a user-defined signal, "wordChanged" or such, to the Good Words list view widget, and catch that signal in the Words View widget. There it would have to look up the word, get its physical index, get the sort/filter proxy to translate that to the sorted row index, and then it could issue the dataChanged signal to get the table View to call the table Model for fresh data.

Now, I dunno. Do I need to add that machinery? If the user can get the current status just by scrolling even a tiny bit (or by hiding the app and revealing it; that does it also), should I bother?