[okular] [Bug 469132] KDE Plasma Printer for HP Colorjet refused to set duplex printer, while Gnome GTK prints duplex w/o

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=469132

ojermo at gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |ojermo at gmail.com

--- Comment #3 from ojermo at gmail.com ---
Same symptom on a third printer, with PPD-level evidence for the cause: Brother
HL-4570CDW with the official Brother CUPS driver
(hl4570cdwlpr/hl4570cdwcupswrapper 1.1.1-5). "Long side binding" / "Short side
binding" radios in Okular's Print → Options are greyed out. Properties →
Advanced → "Two-Sided Printing" exposes a working dropdown that produces real
duplex output.

The PPD declares duplex via a vendor-prefixed keyword: 
$ lpoptions -p HL4570CDW -l | grep -i duplex BRDuplex/Two-Sided Printing:
DuplexTumble DuplexNoTumble *None
— rather than the standard CUPS "Duplex" keyword. The basic dialog appears to
only probe for "Duplex"; the Advanced tab probes the full PPD and works. This
is consistent with bug 473841's finding that the issue reproduces in Qt5
example apps — i.e., the bug is in Qt's QPrintDialog/QCupsJobWidget capability
detection, not in Okular or KDE's print-manager.                                

For the HP printers in this report and 473841, it's worth checking whether
their PPDs also use vendor-prefixed duplex keywords (HPDuplex, HPOption_Duplex,
or similar) rather than the standard "Duplex". If so, the fix would be to make
the basic dialog fall back to recognized vendor keywords — or, more cleanly,
query CUPS for the printer's actual sides/duplex capability rather than
scraping a specific PPD keyword name.                                           

Versions: Fedora 43, Plasma 6.6.4, Frameworks 6.25.0, Qt 6.10.3,
okular-25.12.3, qt6-qtbase-6.10.3, cups-2.4.18.

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