Add support for poppler-qt6 pdf backend

[selmf]

This PR adds support for the Poppler Qt6 backend

@jbeich feel free to give it a test, feedback is always welcome.

[jbeich]

Fails to build on FreeBSD 13.1. Clang is default on FreeBSD, OpenBSD, macOS, Android, OpenMandriva, ChimeraLinux. libc++ is often used together with Clang and generally cannot be mixed with libstdc++ due to conflict between libc++abi (or libcxxrt) and libsupc++. Given YACReader depends on C++-based libraries (Qt6, Poppler) it cannot be built with different C++ library than the default (unless those are bundled).

$ pkg info -x qt6
poppler-qt6-22.11.0_1
qt6-5compat-6.4.1
qt6-base-6.4.1
qt6-declarative-6.4.1
qt6-multimedia-6.4.1
qt6-shadertools-6.4.1
qt6-svg-6.4.1
qt6-tools-6.4.1

Clang/libc++

YACReaderLibrary/initial_comic_info_extractor.cpp:41:25: error: functional-style cast from 'std::unique_ptr<Poppler::Document>' to 'std::unique_ptr<Poppler::Document>' uses deleted function
        auto pdfComic = std::unique_ptr<Poppler::Document>(_pdfComic);
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/v1/__memory/unique_ptr.h:121:59: note: candidate constructor (the implicit copy constructor) has been implicitly deleted
class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr {
                                                          ^

GCC/libc++

YACReaderLibrary/initial_comic_info_extractor.cpp: In member function 'void YACReader::InitialComicInfoExtractor::extract()':
YACReaderLibrary/initial_comic_info_extractor.cpp:41:69: error: use of deleted function 'constexpr std::__1::unique_ptr<Poppler::Document>::unique_ptr(const std::__1::unique_ptr<Poppler::Document>&)'
   41 |         auto pdfComic = std::unique_ptr<Poppler::Document>(_pdfComic);
      |                                                                     ^
In file included from /usr/include/c++/v1/__memory/shared_ptr.h:25,
                 from /usr/include/c++/v1/__functional/function.h:20,
                 from /usr/include/c++/v1/functional:500,
                 from /usr/include/c++/v1/optional:154,
                 from /usr/local/include/qt6/QtCore/qtypeinfo.h:8,
                 from /usr/local/include/qt6/QtCore/qglobal.h:1397,
                 from /usr/local/include/qt6/QtCore/QtCore:4,
                 from /usr/local/include/qt6/QtGui/QtGuiDepends:3,
                 from /usr/local/include/qt6/QtGui/QtGui:3,
                 from ../YACReaderLibrary/initial_comic_info_extractor.h:4,
                 from ../YACReaderLibrary/initial_comic_info_extractor.cpp:1:
/usr/include/c++/v1/__memory/unique_ptr.h:121:59: note: 'constexpr std::__1::unique_ptr<Poppler::Document>::unique_ptr(const std::__1::unique_ptr<Poppler::Document>&)' is implicitly declared as deleted because 'std::__1::unique_ptr<Poppler::Document>' declares a move constructor or move assignment operator
  121 | class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr {
      |                                                           ^~~~~~~~~~

[selmf]

Well I am glad I asked you to test this now.

What is happening here is not a compiler or libstdc++ problem but a mistake on my side.

The compile error is caused by the compiler hitting a line it shouldn't. What is missing here is the #ifdef guard and the poppler-qt6 specific logic for the unique pointer, which is different from poppler-qt5.

[selmf]

Ok, I pushed a fix for the problem and I did a test build with clang, qt6 and poppler-qt6 on my Linux machine.

[jbeich]

725cf65 builds fine with both poppler-qt6 and poppler-qt5. Tested runtime via a PDF version of FreeBSD Journal: dssim for poppler-qt6 (fad24a5) vs. poppler-qt5 (9.10.0) returns 0.00000000 (identical) on a screenshot of a single page.

[luisangelsm]

@selmf maybe we should add a new job(s) in Azure Pipelines for poppler-qt6 to catch problems like the one @jbeich found (thanks for testing btw).

[luisangelsm]

@selmf could you rebase this on top of develop please?

[selmf]

@luisangelsm rebase is up.

Adding a test build for poppler-qt6 to catch errors is absolutely something we need to do. The problem here is that Ubuntu does not package poppler-qt6 yet, so I could not add a test to our build pipelines.