Re: Qt issue with printing landscape-oriented images

[Johannes Meixner <jsmeix@suse.de>]

Hello,

I didn't check any details here
so only a side note for the fun of it:

There is no such thing as "landscape printing".

Cf.
https://en.opensuse.org/SDB:Landscape_Printing


On 2025-02-26 10:25, Zdenek Dohnal wrote:
> 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.
>> 

Kind Regards
Johannes Meixner
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