firefox: stuck in "Preparing Preview" when opening the print dialog

[raboof]

Describe the bug

When I hit 'Ctrl+P' in Firefox, the print preview dialog opens, but shows a spinner and the text 'Preparing Preview'. I can close the dialog with 'Escape'.

Additional context

Removing all printers from 'system-config-printer' seems to have helped (there was one hplip printer in there), and was sufficient for me as I wanted to 'Save to PDF' anyway.

Saw the same behavior both with 'firefox-bin' and 'firefox'.

Metadata

nixpkgs-unstable at 2c7f3c0

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[gaudren]

I also had this problem. I was able to work around it by setting print.prefer_system_dialog to true in about:config

[waltermin]

For my system, I narrowed this down to a problem where Firefox hangs when trying to talk with cups. The moment I stopped cups (sudo systemctl stop cups and sudo systemctl stop cups.socket), Firefox was freed from whatever deadlock it was in, and my print dialog and PDF downloads immediately came back. I ended up stopping cups, deleting /var/lib/cups and /var/spool/cups, and starting cups again, which fixed the problem for me. Maybe some state files that cups stores were corrupted or otherwise problematic?

[hunner]

This issue appeared for me after moving from 24.11 to 25.05. The solution from @saghetti0 worked. /var/spool/cups was empty, and I unfortunately didn't preserve the contents of /var/lib/cups for debugging.

[Majiir]

I also had this issue, and stopping cups and cups.socket immediately fixed it. I don't see anything unusual in the service logs. I have snapshots of /var/lib/cups and /var/spool/cups if anyone has ideas on how to debug this.

[crosson]

So this problem still exists today on an updated version of firefox. The note above about changing print.prefer_system_dialog fixes it. But it raises the question.

What is weird is that this all worked once, then stopped working. It's pretty dissapointing if we have to turn off print preview entirely just to get it to work.

[hunner]

Seems to be fixed in 25.11! (ff version 146)

[abhillman]

I also had this issue, and stopping cups and cups.socket immediately fixed it. I don't see anything unusual in the service logs. I have snapshots of /var/lib/cups and /var/spool/cups if anyone has ideas on how to debug this.

This worked perfectly and restored functionality when I restarted the services! Thank you so much!

[pulpog]

Seems to be fixed in 25.11! (ff version 146)

Sadly not for me, I just encountered it for the first time after setting up cupsd with Firefox already at 146.

[cherusk]

Also ran into this, proper patch seems on the way -> #475079

[HeartBurzum]

For my system, I narrowed this down to a problem where Firefox hangs when trying to talk with cups. The moment I stopped cups (sudo systemctl stop cups and sudo systemctl stop cups.socket), Firefox was freed from whatever deadlock it was in, and my print dialog and PDF downloads immediately came back. I ended up stopping cups, deleting /var/lib/cups and /var/spool/cups, and starting cups again, which fixed the problem for me. Maybe some state files that cups stores were corrupted or otherwise problematic?

This solution worked for me, i moved both folders, but it looks like in the end I was able to move /var/lib/cups back and only /var/spool/cups was the issue after restarting the service it stopped hanging and was able to print.

[Sylvain303]

I tested print.prefer_system_dialog switching, that helped. FF 144.0.2 (64 bits) (mozzila-deb - 1.0) under xubuntu 24.04.

I put back print.prefer_system_dialog to preview mode after removing en ghost / rogue printer:

Which solved the preview not showing up.

So this tend to confirm, that the system printer status could block FF from showing up the print preview.

System printer dialog was not impacted nor blocked.

Hope that helps.

[cherusk]

Would be really super sweet that to get repaired.

Hate the workaround of downloading everything and then to print it via qpdfview or alike ....