Bug 486856

SUMMARY

I think this is a common issue talked here in other platforms https://bugs.kde.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=CONFIRMED&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=RESOLVED&bug_status=NEEDSINFO&bug_status=VERIFIED&bug_status=CLOSED&component=Comicbook%20backend&list_id=2709189&product=okular&query_format=advanced&short_desc=CBR&short_desc_type=allwordssubstr, but in Windows the issue still is there somehow.

Summarizing, actually if you want to open a CBR file in Okular, it needs Unrar or The Unarchiver (since https://bugs.kde.org/show_bug.cgi?id=339370).

However, for Windows:
- The Unarchiver https://theunarchiver.com/ is a Mac app, closed source, and their CLI tool (Unar https://theunarchiver.com/command-line) for Windows is outdated, and I don't know if only with it works or not because I didn't try.
- The only Windows / Free / Open source Unrar i found is from GnuWin32 https://gnuwin32.sourceforge.net/packages/unrar.htm which is almost 20 years old. The other Windows one is RARLAB Unrar what comes bundled with WinRAR, which is Trial / Closed Source https://www.win-rar.com/download.html https://www.rarlab.com/download.htm.

So, in Windows, you rely solely on outdated versions or closed source / trial software.

STEPS TO REPRODUCE

1. In Windows,
2. with Okular 24.04.80,
3. without Unar (Unarchiver Cli Tool), Unrar Free or WinRAR installed,
4. try to open any CBR file.

OBSERVED RESULT

> Could not open file:///E:/ComicBook.cbr. 
> Cannot open document, neither unrar nor unarchiver were found.

EXPECTED RESULT

Open it?

SOFTWARE/OS VERSIONS

- Windows 10 PRO 22H2
- Okular 24.04.80

ADDITIONAL INFORMATION

- For Windows, maybe it's more common a reliable to use https://7-zip.org/ as it has a 7z.exe command line tool that supports RAR.

- As it seems Okular uses KArchive, I could test that it reads without anything else CBZ (Zip) and also CB7 (7-zip) https://bugs.kde.org/show_bug.cgi?id=412413, and It should be doing also CBT (Tar) https://bugs.kde.org/show_bug.cgi?id=204195. 

- Much better solution could be add a backend option which show a few default and autodetected built-in options (Unrar, Unar, 7z...) and maybe a custom option to put a path and command line tool of your preference to deal with the extraction.

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Thanks!

PD.: CBR (RAR), CBA (ACE) and other based in closed format are awful...