Provide graph traits and properties for pmp::SurfaceMesh

[afabri]

Summary of Changes

This PR will make pmp::SurfaceMesh a model of a MutableFaceGraph. It further needs some additional typedefs and postfix increment of pmp iterators which I discuss with the authors.

See http://www.pmp-library.org/ and PR29 and PR30

Release Management

[lrineau]

TODO: add CMake support for pmp (http://www.pmp-library.org/).

[sloriot]

Note that the build system is cmake so it works directly in config mode. It might just be a matter of documentation on our side. Side note, Eigen seems to be required so it should come with a find Eigen.

[MaelRL]

@afabri what is the status of this PR?

[sloriot]

There are still issues in pmp-library in the generatedpmpTargets.cmake:
The following is generated:

set_target_properties(pmp PROPERTIES
  INTERFACE_COMPILE_OPTIONS "-std=c++11"
  INTERFACE_INCLUDE_DIRECTORIES "/home/sloriot/projects/pmp-library.git/src/pmp/../"
  INTERFACE_LINK_LIBRARIES "OpenMP::OpenMP_CXX"
)

while something like that should be generated:

find_package(OpenMP)
if(OpenMP_CXX_FOUND)
set_target_properties(pmp PROPERTIES
  INTERFACE_LINK_LIBRARIES "OpenMP::OpenMP_CXX"
)
endif()

set_target_properties(pmp PROPERTIES
  CXX_STANDARD 11
  INTERFACE_INCLUDE_DIRECTORIES "/home/sloriot/projects/pmp-library.git/src/pmp/../"
)

I don't know how to do it property in the cmake machinery without using a template file.

@mbotsch @dsieger do you see a solution? Note that it is not specific to CGAL but to any project using cmake that do not use OpenMP and/or that use a CXX standard greater than c++11

[dsieger]

Hi Sebastien,

I'm sorry, but to me it's also not obvious what the solution would be.

Regarding the C++ standard I would even say that prescribing the exact version is the right thing to do. Simply using a later standard might lead to incompatibilities / deprecation issues.

Regarding OpenMP I would assume that it is not added to the interface libraries if OpenMP is not found. After all, we only add it conditionally:

find_package(OpenMP)
if(OpenMP_CXX_FOUND)
  target_link_libraries(pmp PUBLIC OpenMP::OpenMP_CXX)
endif()

But then, I'm not too familiar with that part of CMake...