[vtk-developers] Errors in building VTKExamples in today's CVS

[Brad King]

Dave Partyka wrote:
> Bill Lorensen wrote:
>> I'm revamping the Examples tree. As part of that I hope to remove the
>> complexity of the current CMakeLists.txt file. I'm not sure why there
>> is a need for the custom command to build the examples. The current
>> method makes it very difficult to add tests to the examples.
> I think the intention there was so that you could build the examples
> against an installed vtk, though I guess that doesn't make sense as we
> no longer ship libraries, just vtk.exe? I am CC'ing Brad King and Dave
> Cole  as I remember one of them describing this to me a while back. I
> agree though, that whole CMakeLists.txt is probably more complex than
> necessary.

There are multiple reasons for the current approach:

(1) The Examples directory has many executables, which if included in
    the main VTK build crowd VS solution files.

(2) The Examples tree, along with each individual example, should build
    as a stand-alone project against the build or install tree.

(3) Since the Examples tree must always support building as an outside
    project, it is best to keep this well-tested by *always* building
    it that way.

As to the current implementation that meets the above requirements:

(a) The only way to build the Examples tree as an outside project but
    also build it as part of VTK is to drive the outside project with
    a custom target.

(b) The current complexity in the Examples/CMakeLists.txt file is left
    from old versions of CMake whose language was much weaker.

Implementation choice (b) is easy to change.  We can fix it by making
VTK/Examples a totally standalone directory that CMake never enters as
a subdirectory of the main build.  The custom target that drive it now
can be moved to a separate directory.

Implementation choice (a) is not something we can change.  Before it
was done this way we had constant problems with users that were unable
to build projects they copied from the examples because they could only
build in-tree.

Bill, what you seem to want is a new requirement:

(4) The Examples tree should have tests that run as part of the main
    VTK test suite.

Since there is no add_subdirectory() in the main VTK that enters the
real Examples build tree, CTestTestfile.cmake does not include the
Examples tests.  There are two approaches to solving this problem.

(c1) Add a test in the main VTK tree that invokes CTest to run all
     tests from the Examples tree.

(c2) Use the TEST_INCLUDE_FILE property to include the VTK Examples
     test suite in the main VTK test suite:
     http://www.cmake.org/cmake/help/cmake2.6docs.html#prop_dir:TEST_INCLUDE_FILE

I also have some ideas for more complicated solutions but let's not
discuss them if (c1) or (c2) is acceptable.

-Brad