[CMake] ExternalProject_Add examples

[Marcus D. Hanwell]

On Sat, Mar 17, 2012 at 5:03 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Folks,
>
> I've recently created a number of super builds using CMake's External
> Project mechanism. Each external project requires some sort of
> download, configuration, build and possibly install. The CMake defines
> needed to correctly access the results of the external project vary
> significantly. The trickiest part is find the proper download,
> configuration and CMake defines.
>
> For example, for the Point Cloud Library (http://pointclouds.org/) I
> created these external projects:
> VTK - git, cmake, make; VTK_DIR
> FLANN - zip, cmake, make install; FLANN_LIBRARY, FLANN_INCUDE_DIR
> Eigen - .tar.bz2,; EIGEN_INCLUDE_DIR
> Qhull - git, cmake, make;QHULL_LIBRARY,QHULL_INCLUDE_DIR
> Boost - .tar.gz, bootstrap.sh, b2; BOOST_ROOT
> GTest - .zip, cmake, make; GTEST_ROOT,GTEST_INCLUDE_DIR
>
> Slicer4 has many more.
>
> Should we start collecting sample ExternalProject_Add files for
> external projects?

We have talked about doing this too (I have Eigen, Boost, GTest and
others for example). The standard CMake based projects hardly seem
worth it, but it depends on what you want to do with them I suppose.
For the work we are doing in chemistry we have been working on an
experimental superbuild that uses a common prefix in the build tree to
install to, and then all we need pass in is CMAKE_PREFIX_PATH - this
can make the logic significantly easier for dependent CMake projects
as it will always search within the prefix first.

The Qt external project was pretty tricky too, and we are using that
in several places along with smaller libraries like libxml2.

Marcus