System print dialog not setting two-sided flag despite the checkbox Two-Sided being checked

Number:rdar://FB8607294 Date Originated:09/02/2020
Status:Open Resolved:
Product:macOS Product Version:10.15.6
Classification: Reproducible:always
Original submission comment (previously I taught it was related to Preview, but it is related to the system print dialog):
When printing a PDF in Preview using a two-sided capable printer (to CUPS server), checking "Two-Sided" box you expect the printer to output two-sided, but it does not. Debugging on the CUPS print server (error_log with LogLevel=debug) clearly shows what the problem is, the "sides" and "Duplex" flags are not set for two-sided printing. Printing from Adobe Reader (on macOS ofc :D) sets "sides=two-sided-long-edge" and "Duplex=DuplexNoTumble" flags and thus the printer outputs two-sided. I was recently informed about this issue (probably the recent update, don't know that for sure, have not tested with a previous version of macOS), happens on all iMacs and MBPs in our company. I have attached the job logs from the CUPS print server for you to see print flags set by Preview and Adobe Reader.

Comment 1 (Sep 2, 2020 at 5:28 PM) by bug author:
I have done some more testing and I have discovered that it is a bug in the Two-Sided button implementation. Basically here is what I have found out and have been able to reproduce it on other iMacs too:
1. Opening the printing dialog with the Two-Sided box unchecked and checking it, sets the two-sided flags on the print job correctly;
2. Opening the printing dialog again, now with the Two-Sided box checked by default as per our last print job, clicking print will not set the two-sided flags;
3. Opening the printing dialog again, the Two-Sided box is checked by default, uncheck it and check it again, clicking print will again set the two-sided flags correctly.
So basically, when opening the print dialog and the Two-Sided box is checked by default, it is not taken into account and is ignored.
Would appreciate a quick fix for it as we must now use Adobe Reader because of this and it is annoying! Adobe Reader does not memorise last print job setting and we need to click on each print two-sided and grayscale.
Many thanks,

Comment 2 (Sep 2, 2020 at 6:21 PM) by bug author:
Given that this problem is actually related to the system print dialog, I would ask you to set the appropriate category as it is not related to Preview app really.
Thanks, Daniel


Bug Author (Sep 2, 2020 at 11:08 PM)

Further debugging this I found that the problem actually lies in between the two-sided checkbox and the system provided profiles: Black and White, Colour. Basically, using Show Presets in print dialog, I clearly see that they have two-sided off, but when you select it in the drop-down, two-sided checkbox is marked and unless you uncheck and check it again, it will not print two-sided.

By iancudanielc at Sept. 2, 2020, 8:09 p.m. (reply...)

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