Re: [PATCH 06/31] gnu: kwindowsystem: Update to 5.24.0.

[Andreas Enge <andreas@enge.fr>]

On Mon, Aug 01, 2016 at 08:13:17PM +0200, David Craven wrote:
> * gnu/packages/kde-frameworks.scm: Update to 5.24.0.

Here also, mention all changes:

> -        (uri (string-append "http://download.kde.org/stable/frameworks/"
> +        (uri (string-append "mirror://kde/stable/frameworks/"

This.

>      (native-inputs
> -     `(("pkg-config" ,pkg-config)
> +     `(("extra-cmake-modules" ,extra-cmake-modules)
> +       ("pkg-config" ,pkg-config)
>         ("xorg-server" ,xorg-server))) ; for the tests
>      (inputs
> -     `(("extra-cmake-modules" ,extra-cmake-modules)

The move of extra-cmake-modules.

> -       ("qt" ,qt)
> +       ("qtbase" ,qtbase)
> +       ("qtx11extras" ,qtx11extras)

And the switch from the monolithic to the modular Qt.

For qtx11extras that is not found, here is the error message:

CMake Error at /gnu/store/6d3qjij1k7z2sjlsq9c0b8ql53xgn34v-qtbase-5.6.1-1/lib/cmake/Qt5/Qt5Config.cmake:26 (find_package):
  Could not find a package configuration file provided by "Qt5X11Extras" with
  any of the following names:

    Qt5X11ExtrasConfig.cmake
    qt5x11extras-config.cmake

  Add the installation prefix of "Qt5X11Extras" to CMAKE_PREFIX_PATH or set
  "Qt5X11Extras_DIR" to a directory containing one of the above files.  If
  "Qt5X11Extras" provides a separate development package or SDK, be sure it
  has been installed.
Call Stack (most recent call first):
  CMakeLists.txt:54 (find_package)
-- Configuring incomplete, errors occurred!
See also "/tmp/guix-build-kwindowsystem-5.24.0.drv-0/build/CMakeFiles/CMakeOutput.log".
phase `configure' failed after 4.4 seconds

One can go into /tmp/guix-build-kwindowsystem-5.24.0.drv-0 and look at the
file environment-variables. It does contain
export CMAKE_PREFIX_PATH="...:/gnu/store/3a5v3gh59hif13w7jqk8lhp5kvwbwk2i-qtx11extras-5.6.1-1/:..."

This is the installation prefix, and it is added to CMAKE_PREFIX_PATH as
required. Strange!

Inside, in the directory lib/cmake/Qt5X11Extras/, there are
Qt5X11ExtrasConfig.cmake and Qt5X11ExtrasConfigVersion.cmake.

It should be possible to define the environment variable Qt5X11Extras_DIR,
but it would be good to understand the problem...

According to the cmake documentation:
   https://cmake.org/cmake/help/v3.0/command/find_package.html
the Qt5X11ExtrasConfig.cmake file is searched for in the following directories
(the "(U)" stands for "Unix"):
<prefix>/(lib/<arch>|lib|share)/cmake/<name>*/          (U)
<prefix>/(lib/<arch>|lib|share)/<name>*/                (U)
<prefix>/(lib/<arch>|lib|share)/<name>*/(cmake|CMake)/  (U)

In our case, the file is actually in
<prefix>/lib/cmake/<name>/, which should be fine.

The exact failing line 54 of CMakeLists.txt is:
   find_package(Qt5 ${REQUIRED_QT_VERSION} CONFIG REQUIRED X11Extras)
This actually does not correspond to the regular expression for find_package
in the cmake documentation...
I think it actually looks for Qt5Config.cmake, which it finds in qtbase, see
the line in the above error message:
CMake Error at /gnu/store/6d3qjij1k7z2sjlsq9c0b8ql53xgn34v-qtbase-5.6.1-1/lib/cmake/Qt5/Qt5Config.cmake:26 (find_package):
  Could not find a package configuration file provided by "Qt5X11Extras" with
Lines 25 following of Qt5Config.cmake look like this:
foreach(module ${Qt5_FIND_COMPONENTS})
    find_package(Qt5${module}
        ${_Qt5_FIND_PARTS_QUIET}
        ${_Qt5_FIND_PARTS_REQUIRED}
        PATHS "${_qt5_install_prefix}" NO_DEFAULT_PATH
    )
So it looks like "find_package" is called with the argument "Qt5X11Extras",
but also with the suspicious additional parameters
   PATHS "${_qt5_install_prefix}" NO_DEFAULT_PATH
Since we install qt5x11extras to a different directory from qt5base,
the thing following the PATHS keyword is probably wrong.

See the cmake documentation:
"The set of installation prefixes is constructed using the following steps. If NO_DEFAULT_PATH is specified all NO_* options are enabled.
    Search paths specified in cmake-specific cache variables. These are intended to be used on the command line with a -DVAR=value. This can be skipped if NO_CMAKE_PATH is passed:
    CMAKE_PREFIX_PATH
    CMAKE_FRAMEWORK_PATH
    CMAKE_APPBUNDLE_PATH"

So I would say the error message is totally misleading; the NO_DEFAULT_PATH
keyword explicitly disables the CMAKE_PREFIX_PATH.

Unfortunately the store is read-only (in former times, I sometimes modified
store items by hand; now I do not dare overwrite the special file system
flags any more...), otherwise I would have tried to modify the file by hand...

Sorry for the long message, which follows my own path in trying to debug
this mess. To quickly summarise it:
I think we need to modify the qtbase package to drop the
NO_DEFAULT_PATH from Qt5Config.cmake.

Ceterum censeo that cmake should not be used, but this is not our choice;
autotools based projects usually do not create these problems...

Andreas