Manually refresh QListWidget while inserting

Max13

@VRonin Thank you for the hint. It works almost as expected. The scrollbar shrinks but the widget stays empty. But when I focus on another app or refocus on mine, the content on the widget flashes and disappears again.

Is it related to the speed of insertion? Is there a last thing missing?

SGaist

Hi,

How many items are you trying to add ?

In any case, it looks like you should rather consider QListView with a custom QAbstractListModel.

Doing so you will be able to implement smarter algorithm to handle injection of big amount of data like batch insertion maybe a bit of thread to offload the work from the main thread etc.

Hope it helps

Max13

@SGaist Thanks for the suggestion. Currently, I'm adding as much directories and files in a selected folder on the computer. So it can be from 1 to ... elements.

Before subclassing all that, I made another class which receives the QListWidget and has a crawl method. When crawling, I tried to call: QtConcurrent::run(crawler, &Crawler::crawl), which works correctly but still freezes the GUI. Is that what you suggested?

EDIT: BTW, I'm adding them by creating QListWidgetItems 1 by 1.

Max13

I was using QFuture<T>::waitForFinished() which was blocking the main thread. I now send a signal when it's finished and return peacefully to the main loop.

I'm still unable to see the changes in the list, live. Doing a refresh (using refresh or QApplication::processEvents()) will refresh all the list, is it possible to only "commit" the last added element?

SGaist

Why not use a QFileSystemModel ?

Max13

@SGaist Because I think it would be more expensive to use this model then parse it searching for what I have to hide. So I thought, it would be faster to just recursively parse the filesystem myself and immediately sort what I need to keep or hide. Isn't it?

SGaist

You can add custom QSortFilterProxyModel that will remove what you don't want.

Max13

@SGaist Actually, "sorting" here means I have to exclude considering characteristics, like filename length. For real, is it heavier to feed the widget myself, than using the Model, View and sorter?

If you say so, as a forgotten Qt Ambassador I can only trust a permanent Qt Champion ;)

But I still would like to know what's the problem with my code. Anyway, I will look for the issue later

SGaist

It's rather the filter part that is interesting in that class for your use case.

Not knowing your code I can't comment ;)

Max13

Finally... After few docs and experiences, I don't know how but I missed the fact that QWidgets are not reentrant (thanks to @kshegunov), and I also missed the fact that signals and slots are made for that.

@SGaist So, thanks for your advices but doing real MVC made my app too complicated for what it does. In a more constructed project, I would do what you suggested. I've simplified mine:

Choose your "root" directory
The Crawler crawls (recursively in Qt::Concurrent) and send a signal when the QFileInfo::fileName().length() is more than x characters
A slot in the MainWidget adds the item in the QListWIdget

That's all for now (auto-rename for later), so few lines of code. Thank you for your advices.