Create widgets in another thread

[bfbrmt]

I create some widgets in another thread and add them to window. All work fine.
Many people told me that this is not allowed in qt.
I wonder whether this is ok.
My code: https://github.com/huangdade/CreateWidgetsInAnotherThread
At beginning, I moved the widgets to main thread. But I found it still works without that.

[JKSH]

@bfbrmt said in Create widgets in another thread:

I create some widgets in another thread and add them to window. All work fine.
Many people told me that this is not allowed in qt.

No, it is not allowed in Qt. Widgets are not reentrant or thread-safe.

But I found it still works

It can work today and crash tomorrow.

[ChrisW67]

@bfbrmt said in Create widgets in another thread:

I create some widgets in another thread and add them to window. All work fine.

Why? What problem do you think you are solving?

[J.Hilk]

you guys are over reacting, the @bfbrmt thinks he's creating QWidgets in an other thread. But he's calling the createWidgets function from the GUI thread. That means the createWidgets function itself is also executed in the GUI thread.

Still, @bfbrmt try not to create QWidgets in any thread, but the one where your QApplication resides in.

[bfbrmt]

This post is deleted!

[bfbrmt]

@JKSH What if I move thoese widgets to main thread? Will it be safe?

[bfbrmt]

@ChrisW67 I needs to create many custom widgets and add them to a layout. The custom widget is complicated and the creation costs about 20ms for each. I want to create them in sub thread and move them to main thread. How about this idea?

[JonB]

@bfbrmt said in Create widgets in another thread:

I want to create them in sub thread and move them to main thread. How about this idea?

You can't, as commented above. You must create/manipulate QWidgets only in the main, UI thread. Doesn't matter how much you "want" to do it in a secondary thread, you must not.

Creating a widget does not take 20ms. It is possible your computations for what you want in the widget might take time, but not the widget creation itself. If this is the case you must use signals & slots: the secondary thread can parcel up necessary non-QWidget information as it pleases, and then send that via a signal, with the main UI thread having a slot on that where it interprets the information to create an appropriate widget.

[JoeCFD]

@bfbrmt Just curious: what causes the creation of your widgets to take so long? If some works need to be done inside the creation, throw the works into a thread and create your widgets after they are done.