[Okular-devel] Review Request 111829: Use DPI of current screen for PDF rendering

[Eugene Shalygin]

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This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/111829/
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(Updated Jan. 13, 2014, 12:39 a.m.)


Status
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This change has been marked as submitted.


Review request for Okular and Albert Astals Cid.


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


Repository: okular


Description
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This patch relies on master branch of LibKScreen.
This patch does not solve the problem in bug completely, but makes Okular behaviour more correct (see below).

The problem (in the bug) is that Okular uses fixed DPI for PDF rendering (72.0 dots per inch) and therefore scale of rendered document becomes incorrect. With current mainline laptop screens having DPI easily twice larger than this constant (72), the problem shows itself quiet strongly.

Additional problems araise with multiscreen configuration, when 1) DPI of each individual screen may be different, and 2) there is no tools in Qt to detect DPI of individual screens in virtual desktop mode. Therefore XRandr has to be used for DPI detection. Raw XRandr is bad dependency for Okular and libkscreen is proposed instead.

This patch approach to the solution in the following way:
1. libkscreen detection staff is added to CMakeLists.txt and config.h
2. It changes Utils::realDpi() function to use libkscreen if present. With libkscreen the function looks for output that contains maximal part of given widget (suppose to be used for document rendering) and returns DPI of that screen.
3. Genenerator interface is extended by adding UtilizeDPI feature and setDPI() method, that is called by Document class right before calling loadXXX() if the generator supports this feature
4. Poppler generator is changed to support UtilizeDPI feature.
5. PageSizeMetric enum is extended with Pixels value to explicitly say that page size is defined in screen pixels (see my posts in the bug); Poppler generator uses this case.


To completetly fix the bug, Document must invalidate generated pixmaps after the widget movements into another screen. I do not know how to track this without subclassing the main window class. Therefore I decided to publish this part of work to get your responce, especially regarding item 3 (Generator class changes).

In the current state, manual reloading of a document after moving Okular to another screen fixes the scale, that is, in my eyes, is quiet helpful already.

Even if we subclass the Okular main window, I do not know what to do when Okular is used as KPart. 


Diffs
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  CMakeLists.txt 217337f 
  config-okular.h.cmake 7217f8d 
  core/document.cpp 3af92c8 
  core/generator.h a5a971b 
  core/generator.cpp 41beb92 
  core/generator_p.h b59293a 
  core/utils.h 8d5d5fc 
  core/utils.cpp 5dd8448 
  generators/poppler/generator_pdf.h 5d5853a 
  generators/poppler/generator_pdf.cpp 1a44523 

Diff: https://git.reviewboard.kde.org/r/111829/diff/


Testing
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Manual. In all screens, that report correct physical size to XRandr, size of documents is correct


Thanks,

Eugene Shalygin

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