[vtk-developers] VTK module system uplift to CMake 3.0 features

[Marcus D. Hanwell]

On Mon, Mar 2, 2015 at 7:49 PM, Ben Boeckel <ben.boeckel at kitware.com> wrote:
> On Mon, Mar 02, 2015 at 17:49:42 -0500, Marcus D. Hanwell wrote:
>> Perhaps because removing/deprecating vtkMPI.cmake etc would change the
>> build system interface. Traditionally the VTK build system has been
>> fairly static, and people come to rely on CMake code. Not sure that is
>> a major consideration at this stage, but it should be considered. I
>> know we have had a number of people ask about the instantiator CMake
>> code...
>
> My plan was to keep all changes, to start, local to
> vtkModuleMacros.cmake. This would ensure that code written for the old
> API would still work (well, as far as CMake uses the API at least). Any
> functions which would now be unnecessary would cause warning messages
> based on a flag so that users/developers would have an upgrade path
> (though whether to default to ON or OFF is a valid question).

Sounds like a good plan.
>
>> My main objection is that Ubuntu LTS 14.04 has CMake 2.8.12.2, and
>> that is the most recent LTS (next is out next year I believe). CMake
>> is reasonably easy to obtain/install locally updated versions, but
>> LTS/distro CMake versions present an additional barrier. If people
>> agree it is worth it then we should go with it, but a number of people
>> tend to use LTS/enterprise versions to simplify upgrade cycles (3.0
>> was tagged June 10 from the looks of it).
>
> I think a PPA is fine for developers. I don't expect VTK 6.3 or whatever
> version it ends up in to even be a thought for LTS.
>
Just to be clear I wasn't thinking about packaging VTK, I was thinking
about the experience for a developer/user compiling from master or a
release. We have generally managed to keep our initial compile
instructions to (more or less) clone/download VTK sources, run system
CMake, compilers, OpenGL etc. We would likely bump that to
download/compile CMake/add a PPA, then do the other stuff.

If we can make it even easier for end users not wanting to compile the
latest and greatest by providing PPAs and similar for other distros
that would be a big step forward for those cases (although we would
need to see how much extra effort was involved too). There are several
projects doing this already in order to get the latest releases
without any need for downloading, unpacking, compiling, etc for thoese
just wanting to use their binaries.

Marcus