Phonon

[Trever Fischer]

> Hi all,
>
> On Thursday 10 March 2011, Ben Cooksley wrote:
>> Hi all,
>>
>> I have found recently that I cannot build KDE Runtime. In tracing
>> this, I ended up with an obscure error:
>>
>> CMake Error at
>> /opt/trunk-kde/kde/share/apps/cmake/modules/MacroEnsureVersion.cmake:95
>> (NORMALIZE_VERSION):
>>   NORMALIZE_VERSION Macro invoked with incorrect arguments for macro
>> named:
>>   NORMALIZE_VERSION
>> Call Stack (most recent call first):
>>   phonon/CMakeLists.txt:18 (macro_ensure_version)
>
> When calling normalize_version(), the version variable should be put in
> quotes, this way even if it is empty it at least becomes an empty string
> instead of nothing.
>
> NORMALIZE_VERSION( "${found_version}" found_vers_num )
>
>> This error message actually means that PHONON_VERSION is empty.
>> Further diagnosing this, I noticed that Phonon recently made changes
>> to where they stored the version string, yet they updated their CMake
>> files.
>>
>> Digging further, I discovered that CMake wasn't using the new ones,
>> because they are being installed to $prefix/share/phonon-buildsystem/
>
> That's not a good idea. Don't do that. Or only do it if you are really
> sure
> you know what you are doing.
phonon-buildsystem is only used to build the backends. Applications should
*not* be using the stuff in there. If they manage to find FindPhonon.cmake
from phonon-buildsystem, the application's build has a bug. Our
FindPhonon.cmake looks for FindPhononInternal.cmake, which adds some build
magic for the backends, such as telling them we have pulseaudio support,
where to install the backend library, and some standard compilation flags
across all backends.

>
>> instead of the standard location ( $prefix/share/apps/cmake )
>
> Although kdelibs install both cmake find-modules as well as it's own cmake
> info-files there, it is not a standard location in any way. For KDE5 this
> will be different.
>
>
> I just had a look at cmake/CMakeLists.txt in phonons git.
>
> Now this does not look good:
>
> set(BUILDSYSTEM_INSTALL_DIR ${SHARE_INSTALL_PREFIX}/phonon-buildsystem/)
> install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in
>               ${CMAKE_CURRENT_SOURCE_DIR}/FindAutomoc4.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/FindPackageHandleStandardArgs.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/FindPhonon.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/FindPhononInternal.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/PhononMacros.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/FindQt4.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/MacroEnsureVersion.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/MacroLogFeature.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/MacroOptionalFindPackage.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/MacroPushRequiredVars.cmake
>               ${CMAKE_CURRENT_SOURCE_DIR}/PhononMacros.cmake
>         DESTINATION ${BUILDSYSTEM_INSTALL_DIR})
>
>
> Why do you think that Phonon needs to install that many Find-modules ?
>
> This means you have to take care of keeping compatibility for them !
> (it's not often that I use the exclamation mark).
> Who is your cmake guy who does that ?
Harald handles most of the cmake stuff. We only install all those because
only the building of the phonon backends need them. There is no urgent
need to keep compatability with them since there is a total of 5
consumers, all of which we keep eyes on.
>
> Second, it makes no sense for package Foo to install a FindFoo.cmake for
> itself.
> So, don't install FindPhonon.cmake.
>
> Sorry, FindPhonon.cmake itself looks bad, delete it and start from
> scratch:
>
> if (NOT PHONON_BUILDSYSTEM_DIR)
>     find_program(PC_EXECUTABLE NAMES pkg-config
>     PATH_SUFFIXES bin
>     HINTS
>     ${CMAKE_INSTALL_PREFIX}
>     ONLY_CMAKE_FIND_ROOT_PATH
>     )
>
>
> There is a FindPkgConfig.cmake, why don't you use that ?
>
> Beside, Phonon itself uses cmake, so install a cmake Config.cmake file.
> This
> file can contain all the information about the installed phonon you want.
> There is absolutely no need for *requiring* pkg-config.
> Especially not in a FindPhonon.cmake which is only found if the
> "searching"
> project already knows where Phonon is.
>
>
> ...
>
> if (PHONON_BUILDSYSTEM_DIR)
>     set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${PHONON_BUILDSYSTEM_DIR})
>
>     if (Phonon_FIND_REQUIRED)
>         set(_req REQUIRED)
>     endif (Phonon_FIND_REQUIRED)
>     if (PHONON_FIND_QUIETLY)
>         set(_quiet QUIET)
>     endif (PHONON_FIND_QUIETLY)
>
>     find_package(PhononInternal ${_req} ${_quiet})
> else (PHONON_BUILDSYSTEM_DIR)
>     if (_data_DIR)
>         if (Phonon_FIND_REQUIRED)
>             message(FATAL_ERROR "ERROR: FindPhonon.cmake not found in
> ${_data_DIR}")
>         endif (Phonon_FIND_REQUIRED)
>     else (_data_DIR)
>         if (Phonon_FIND_REQUIRED)
>             message(FATAL_ERROR "ERROR: Either pkg-config can not find its
> phonon config, or you are not using a recent enough Phonon version.")
>         endif (Phonon_FIND_REQUIRED)
>     endif (_data_DIR)
> endif (PHONON_BUILDSYSTEM_DIR)
>
> There is the macro find_package_handle_standard_args().
> Use that and remove all the code above.
>
> If you have question about how to do things properly with cmake, don't
> hesitate to ask on kde-buildsystem at kde.org or cmake at cmake.org.
> This would be much better than spreading such code.
>
> Alex
> _______________________________________________
> kde-multimedia mailing list
> kde-multimedia at kde.org
> https://mail.kde.org/mailman/listinfo/kde-multimedia
>


-- 
Trever Fischer (tdfischer)
Fedora Ambassador, KDE Hacker
http://wm161.net
GPG: C40F2998 hkp://wwwkeys.pgp.net