veronica

veronica, 16 days ago

I have experimented with a lot of solutions, including sip.delete and setting Qt.WA_DeleteOnClose, and those are even worse (kind of expected).

What I've tried now is to call setParent(None) instead in the closeEvent, and that definitely triggers the class del on the Python side, and seems to reduce the number of QWidgets in the app back to the expected value.

Anyone with some experience with this that can advice?

veronica, 16 days ago

Do you do any Python + Qt work, @carlschwan?

veronica, 16 days ago

There is definitely an issue here arising from Qt and Python both having a garbage collector that don't really talk to each other.

The easy solution is to not tell Qt to do anything at all, and just keep adding more stuff into memory, or try to re-use dialogs. However, re-use comes with the complication of having to clear old content first, and I also have dialogs that are used in multiple instances simultaneously with different content.

veronica, 16 days ago

@ogi Thanks! I'll have a read through that.

Yes, deleteLater is clearly risky. I believe it is safe for on-the-fly generated context menus, which I delete after the exec call returns, but I really want a better solution for dialogs.

veronica, 16 days ago

@liamcollod Yeah, not relevant as far as I can tell.

Edit: To clarify, it's not the Python garbage collector that causes the problem, but that the one in Qt runs too early. Hence the Python-side RunTimeError that occurs when the C++ object is suddenly gone.

veronica, 16 days ago

@carlschwan Yes, it's much cleaner in pure C++ where there is only the Qt garbage collector to take into account. 😅

veronica, 15 days ago

Ok, so the status:

Disconnecting the QDialog from its parent seems to free up the object to be deleted, but as long as the Python side holds on to it, it stays alive. As soon as it runs out of scope on the Python side, the del method is called on it, which in my case just prints a debug message that the object is deleted.

Monitoring the widget count on the Qt side, and the memory allocation on the Python side, seems to confirm that the memory is freed. No segfaults observed in known cases.

veronica, 15 days ago

@ogi I had some success with setParent(None) under stress tests (long running job triggered by a singleShot) and it didn't crash. The dialog closed gracefully and got deleted safely (the del method was triggered). Widget count is freed, and so is (Python side) memory usage.

The only places where I have to keep my deleteLater calls is on context menu objects that are generated on the fly. Otherwise, each menu trigger adds one more entry to the global widget count.

Interesting results.

veronica, 15 days ago

@ogi These specific ones are menus that change every time they're clicked. So they're generated on the fly depending on what you click on.

One example is the text editor right click menu, which has actions depending on where in the text you clicked, and spell checking suggestions if you click on a misspelled word, etc.

Other menus are permanent.

veronica, 15 days ago

@ogi Example: https://github.com/vkbo/novelWriter/blob/206ca6040ec762b120305440b1190f9b4e55c583/novelwriter/gui/doceditor.py#L1095

veronica, 15 days ago

@ogi Yeah, the whole deleteLater thing I've been doing was triggered by me adding a "--meminfo" debug flag to my app months ago where I started to look at the numbers. 😅

My app now returns to the low water mark of 409 widgets after each dialog/menu/messagebox close. It clears a good deal of used memory too.

veronica, 15 days ago

@ogi Yes, I'm finding these issue thread very useful. Thanks for sharing!

There isn't much pyqt/sip code to look at, so it's a bit hard to figure it out.

veronica, 16 days ago

@atlefren @aslakr Mye CMOT Dibbler viber der ja (for de som har lest Discworld).

veronica, 16 days ago

@janamarie Very nice!

veronica, 17 days ago

@carlschwan Fantastic!

The QTextDocument really needs better support for HTML. I just gave up on it for my own project and I'm now building documents with QTextBlockFormat and QTextCharFormat instead.

The ODT writer is also very limited. I already implemented my own a long time ago.

veronica, 17 days ago

@carlschwan Now, if someone could just add support for line height in QPlainTextDocument, my users would be very happy. 😁

veronica, 17 days ago

@carlschwan The issue in QPlainTextEdit (and QPlainTextDocument) is that it has a much simplified layout engine based on a fixed line height. I suspect that's why it's not there. But neither editor has a line height default property. It has to be set on the text block level, which is inconvenient. The plain text layout engine ignores this setting in either case. At least last time I looked at the source (probably 6.4-6.5 or something).

veronica, 17 days ago

@markus In as much as the plan is to do whatever I feel like doing, when I want to, yes. I have a plan 😁

I have a few things I want to get done though, like put shelves in my storage unit in the garage of the building.

veronica, 17 days ago

@KaraLG84 I saw it when it came out, and as I recall, Jeff Goldblum was the only thing good about that film!

veronica, 19 days ago

@kvaks @marta Nå er det fra E24 da, så jeg tar det med en klype salt til jeg ser en direkte kilde.

veronica, 19 days ago

@marta @kvaks Jeg mener akkurat det jeg sa.

veronica, 19 days ago

@_noelamac_ @zorinlynx Hence the nickname "mansplaining as a service".

veronica, 19 days ago

@Patricia Of course, as an academic, I'm very sceptical of any claim not supported by evidence. Management is, and always has been, mostly just that.

Myers-Briggs anyone?