[Okular-devel] [Bug 268757] New: [Patch] Constant DPI in PDF backend results in incorrect size of pages on screen

[Eugene Shalygin]

https://bugs.kde.org/show_bug.cgi?id=268757

           Summary: [Patch] Constant DPI in PDF backend results in
                    incorrect size of pages on screen
           Product: okular
           Version: unspecified
          Platform: Gentoo Packages
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: PDF backend
        AssignedTo: okular-devel at kde.org
        ReportedBy: eugene.shalygin at gmail.com


Created an attachment (id=58122)
 --> (http://bugs.kde.org/attachment.cgi?id=58122)
Path to fix page size in Okular

Version:           unspecified (using KDE 4.6.1) 
OS:                Linux

Currently, poppler generator uses fixed DPI values (72) for generating images
of PDF pages. If display DPI is not equal to 72, this results in incorrect
scale of pages. Since monitors with large DPI will be more and more popular,
this problem will be more and more significant.

This issue was fixed initially by pino (see bug #191614) but the fix lead to
other problem (#204386) in dual-head X configurations.

I beleive that root of the problem is that in Okular core code "Points" is used
both as typographic point (unit of length) and as measure of page scale that
leads to mess and cause a problem either here or there. For example, in poppler
backend size of page is defined in Points, but actually it is pixels,
multiplied by 72.

To fix this I propose to add the "Pixels" member to
Okular::Generator::PageSizeMetric enum.

To address issue with dual-heads, Utils::realDPI() can be used in Poppler
Generator class instead of Utils::dpi().

Proposed patch is attached. I tested it with dualhead where heads have
different size (in millimeters). The pages on larger monitor is larger, of
course, but the y have the width to height ratio.

Reproducible: Always

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