Re: Qt issue with printing landscape-oriented images

Hi Alex,

thank you for heads-up!

To be honest I have never seen IPP attribute landscape  :D - I know 
there is IPP attribute 'orientation-requested' which is used for setting 
whether you want portrait, landscape, etc.

Based on the code for image it looks like landscape is really a thing, 
and if okular wants to do landscape this way, it should pass 
landscape=true instead of false.

The older cups-filters ignores anything besides landscape=true, but the 
current libcupsfilters sets "auto-rotate" if landscape=false is passed, 
which looks correct to me.


Zdenek

On 2/18/25 15:18, Alexander Pevzner wrote:
> Hi!
>
> This information may be interesting for printing stack maintainers of 
> various Linus distros (Zdenek?).
>
> I've already posted it into the OpenPrinting Telegram group, but as 
> not everybody subscribed to the group, I repost it here, by Till's 
> advise.
>
> We've recently noticed, that the Okular (Qt-based image viewer) 
> incorrectly prints images in the landscape orientation.
>
> When printing image (see attached test.png) it sends the following 
> Create-Job request, followed by the image, converted to PDF (see 
> attached 00000020-data.pdf:
>
> -----
> IPP: request message:
> {
>     VERSION 2.0
>     OPERATION Create-Job
>
>     GROUP operation-attributes-tag
>     ATTR "attributes-charset" charset: utf-8
>     ATTR "attributes-natural-language" naturalLanguage: en-us
>     ATTR "printer-uri" uri: 
> ipp://localhost/printers/Kyocera_ECOSYS_M2040dn
>     ATTR "requesting-user-name" nameWithoutLanguage: pzz
>     ATTR "job-name" nameWithoutLanguage: bug.png
>
>     GROUP job-attributes-tag
>     ATTR "media" keyword: A4
>     ATTR "sides" keyword: one-sided
>     ATTR "landscape" boolean: false
>     ATTR "number-up" integer: 1
>     ATTR "number-up-layout" keyword: lrtb
>     ATTR "job-billing" nameWithoutLanguage:
>     ATTR "job-priority" integer: 50
>     ATTR "job-sheets" nameWithoutLanguage: none none
> }
> -----
>
> It can be reduced down to the very simple Qt example:
>
> -----
> #include <iostream>
> #include <QApplication>
> #include <QPrinter>
> #include <QPrintDialog>
> #include <QImage>
> #include <QPainter>
>
> int main(int argc, char* argv[])
> {
>     QApplication app(argc, argv);
>     QPrinter printer;
>     printer.setPageOrientation(QPageLayout::Landscape);
>     QImage img("./test.png");
>     img = img.scaled(printer.width(), printer.height(), 
> Qt::KeepAspectRatio, Qt:
>     QPainter painter(&printer);
>     painter.drawImage(0, 0, img, 0, 0);
>     painter.end();
>     return 0;
> }
> -----
>
> The problem is obviously in the ATTR "landscape" boolean: false 
> attribute. This is definitely at the Qt side. Seems like all existing 
> versions of Qt are affected.
>
> We have submitted PR agains qt-base, it is pretty trivial and 
> currently on review:
>
> https://codereview.qt-project.org/c/qt/qtbase/+/624835
>
> I believe, all more or less modern Linux distros are affected and 
> wonder why nobody complained before
>
> Note, the problem doesn't exist with old versions of the cups-filters 
> (I was able to test with very old version1.28)
>
> Looks like the landscape attribute attribute is silently ignoring by 
> these old versions, and without this explicit orientation setting, 
> filters set correct orientation automatically.
>
-- 
Zdenek Dohnal
Senior Software Engineer
Red Hat, BRQ-TPBC