1755974 - New Print dialog with CUPS: pages-per-sheet doubled up with system dialog

Status: RESOLVED FIXED

(Core :: Printing: Setup, defect, P3)

Description

[L.I.A.R.]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:97.0) Gecko/20100101 Firefox/97.0

Steps to reproduce:

Context: I have a "Sharp MX M266Nv" printer, configured with CUPS, using driver for "SharpMX-M264Nv PS 1.0"

• I opened the following two scientific papers in FF (PDF.js)
  https://proceedings.neurips.cc/paper/2020/file/28538c394c36e4d5ea8ff5ad60562a93-Paper.pdf
  https://arxiv.org/pdf/2110.03209.pdf
• I attempted to print the first using the "New" FF dialog configured to use "two sided printing: long-edge" + "Pages per sheet: 2"
• I started to configure identically the "New" FF dialog for the second one, then switched to "Print with System Dialog" and configured same options

Actual results:

• First paper got printed single-sided
  I already experienced that multiple times, that's why I decided to switch dialog for the second paper: two sided printing works with system printing but not with FF's dialog
• Second paper got printed 4 pages/pages and 2 sided.
  It seems that both configurations were taken into account!

Expected results:

• Using "New" FF's printing dialog should be able to print 2 sided when system dialog is
• When switching from FF dialog to system dialog, already configured options should be transfered and then only configuration present in System dialog be taken into account. A combination of the options from both dialog should never occur.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Printing: Setup' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[Emily McDonough [:alaskanemily]]

I suspect this is because we perform our own pages-per-sheet transformations in platform code, but only ever rely on the system printing code to do simplex/duplex. That probably means that both Firefox and the print backend did the pages-per-sheet transformation, effectively doubling it. I will look at ignoring our own pages-per-sheet setting when using the system dialog.

Comment 3

[Jonathan Watt [:jwatt]]

Attachment: Bug 1755974 - Prevent pages-per-sheet on macOS being double applied by system print dialog. r=alaskanemily

Note: NSPagesAcross/NSPagesDown is internal API to Apple and is basically
unknown to the Internet. I dscovered it by digging through printing structs in
a debugger while trying to find out how the pages-per-sheet information was
being communicated internally in Cocoa. However, after finding it, I see Google
knows about a grand total of 18 pages on the Internet that mention it, all as
part of debug info dumps. That's still helpful though, since it shows that
these two dictionary entries have been in use since at least 2008, giving some
confidence about backwards compatibility and that it will likely remain in use.

Related to these dictionary keys, Apples official documentation claims that
there are similarly named keys called NSPrintPagesAcross/NSPrintPagesDown:

https://developer.apple.com/documentation/appkit/nsprintpagesacross
https://developer.apple.com/documentation/appkit/nsprintpagesdown

However, I couldn't get those to work, either to read values or to set values.
The references I could find to them on the Internet were in debug output and
people also stating they couldn't get them to work. I have to wonder if someone
at Apple changed the names at some point and forgot to update the
documentation?!

Finally, note that NSPrintPagesPerSheet is long deprecated and nowadays just
has a dummy value of "1" hardcoded.

https://developer.apple.com/documentation/appkit/nsprintpagespersheet

Comment 4

[Jonathan Kew [:jfkthame]]

Ugh, gotta love it when the documentation and the APIs don't match.... congratulations on tracking things down here.

Does this also affect the issue of whether duplex gets applied properly from the new dialog? (First "actual results" indicated it didn't work.)

Comment 5

[Jonathan Watt [:jwatt]]

Thanks! Regarding duplex, I am fixing that in a separate patch.

Comment 6

[Phabricator Automation]

Comment on attachment 9307506 [details]
Bug 1755974 - Prevent pages-per-sheet on macOS being double applied by system print dialog. r=alaskanemily

Revision D164317 was moved to bug 1805477. Setting attachment 9307506 [details] to obsolete.

Comment 7

[Jonathan Watt [:jwatt]]

Attachment: Bug 1755974 - Fix Linux system print dialog to take the pages-per-sheet from print preview. r=dholbert

Comment 8

[Jonathan Watt [:jwatt]]

(In reply to Jonathan Watt [:jwatt] from comment #5)

Regarding duplex, I am fixing that in a separate patch.

I filed bug 1805429 for the duplex issue.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4d41c789765d
Fix Linux system print dialog to take the pages-per-sheet from print preview. r=dholbert

Comment 10

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/4d41c789765d

Comment 11

[Daniel Holbert [:dholbert]]

I'm not entirely sure this was actually fixed (and it actually got slightly-worse with the changes in bug 1805716 that landed in the Nightly immediately after this one).

See bug 1919414 for more details...

Comment 12

[Daniel Holbert [:dholbert]]

(more details in bug 1919414 comment 3 in particular)