Crashes on blank paste

[jamaggs]

Hello

First of all, thanks very much - what a great program!

This is a minor but irritating bug as it has the potential to lose material since the last save. If there is nothing in the clipboard and you try to paste, the program crashes. Running from the terminal shows: Segmentation fault (core dumped).

Linux mint 22.1
Novelwriter 2.7.5
Installed and kept up to date from the ubuntu ppa (ppa:vkbo/novelwriter)

Many thanks!

James

[vkbo]

I can't reproduce this from the description. I cleared the clipboard by command line, and pasted into novelWriter, and nothing happened. On Ubuntu 24.04.

Are you sure there is nothing else interfering here, or some other mime data type being pasted?

A segmentation fault usually indicates it is the Qt library itself crashing. Sometimes this happens because of a race condition between the Python garbage collector and Qt's, but I'm not sure that's the case here. Could you check in Help > About Qt what version of Qt you're on? If you run from command line with the -d flag, this is also printed on the first few lines of output.

[vkbo]

Also, is there a difference between a Ctrl+V paste and via the Edit menu? The former is handled directly by the Qt library, while the second is processed by novelWriter first. If you run from the command line with the -d flag, the latter will print a debug message Requesting action: PASTE. The former will say nothing since it's a direct action.

[jamaggs]

Hello, thanks to the reply.

The paste method doesn't seem to make a difference.

What I did was to log in to Xfce to ensure the clipboard is empty. I then tried to paste in four ways:

1. Ctrl+V
2. Paste from main menu
3. Middle click
4. Paste from context menu

All had the same effect.

I have attached the debug output which includes the qt version etc.

Many thanks

James

log.txt

[vkbo]

I managed to reproduce the issue by running novelWriter with the system Qt libraries on Ubuntu 24.04, which are version 6.4.2, same as yours. When running with the Python environment on Qt 6.10, there is no issue, so this is clearly a Qt bug of some kind.

This is really tricky to fix though as I can't really do anything with segmentation faults on the library side of it. All I can do from the Python code is add ways to avoid triggering the bug – whatever the bug is. All novelWriter does is call self.paste() when it receives a paste action via its own code path. I could potentially add some code to intercept it there, but I need to do some testing to see if a direct paste in the widget is actually intercepted too. Otherwise it will solve nothing.

Could you try the AppImage and see if the issue exists there too? The AppImage is built with Qt 6.9, so it should in theory work for you as well and avoid the bug.

Edit: It could also be a bug in PyQt, which seems to be on version 6.6.1 for both of us. I've had several issues with PyQt6 lately.

[jamaggs]

Hello

Thanks very much for your help. I can confirm that the AppImage works fine. Also, if I upgrade PyQt6 using pip the issue disappears, so I'm guessing it's a problem with the specific version of that.

Many thanks

James

[vkbo]

Yeah, I suspect maybe PyQt6 is the source of the trouble. I've had several issues with it not mapping types correctly to Qt6 too. The Python to C bindings are generated, and I think PyQt6 is less well maintained than PyQt5 was. I've looked into switching to PySide6, which is the official Python bindings, but that runs into other issues.

I'll see if I can make a workaround for 6.4. I kind of want to bump the requirement to 6.5 or 6.6 actually, because there are some improvements there that novelWriter uses and has to check version before accessing. But that will effectively make the Debian package unusable on everything but the latest Debian-based distros.

The workaround will not be added to 2.7 though, unless I really have to. 2.8 release is just around the corner.

[vkbo]

Ok, looks like I can intercept the paste by re-implementing insertFromMimeData. That will likely be useful for a future planned change anyway, so I can try that.

Edit: This does the trick ...

    def insertFromMimeData(self, source: QMimeData | None) -> None:
        if source and source.hasText():
            return super().insertFromMimeData(source)