COMP: Do not include "SlicerBlockSetCMakeOSXVariables" before project()

WORK IN PROGRESS ...


From Jc:

Hi Brad,


To summarize, the user build a building using a line similar to:

  cmake -DSlicer_DIR:PATH=/path/to/Slicer-build -DCMAKE_BUILD_TYPE:STRING=Release ../MyPlugin

  Passing Slicer_DIR is the only requirement.

// ------------------
You are right the file in source/build tree won't help.

// ------------------
Currently, the value for CMAKE_OSX_* are set in SlicerConfig.cmake and I would like the plugin to use these. The current approach is to force the following convention:

    set(EXTENSION_NAME "Foo")

    find_package(Slicer)
    include(${Slicer_USE_FILE})

    [...]

where project() was called within the Slicer use file.


// ------------------
By using this new approach:

   find_package(Slicer COMPONENTS ConfigurationPrerequisites)

   project(Foo)

   find_package(A ..)
   find_package(B ..)

  Can I be sure that the first call to "find_package" will be done before language feature are enabled ?



Thanks
Jc

// --------------------------
From Brad:

On 04/19/2013 10:54 AM, Jean-Christophe Fillion-Robin wrote:
>   cmake -DSlicer_DIR:PATH=/path/to/Slicer-build -DCMAKE_BUILD_TYPE:STRING=Release ../MyPlugin

Great, so find_package doesn't actually need to search but only
load the package config file.

> Currently, the value for CMAKE_OSX_* are set in SlicerConfig.cmake
> and I would like the plugin to use these. The current approach is
> to force the following convention:
>
>     set(EXTENSION_NAME "Foo")
>     find_package(Slicer)
>     include(${Slicer_USE_FILE})
>
> where project() was called within the Slicer use file.

Instead of the above three lines, try these three::

 project(Foo NONE)
 find_package(Slicer)
 SlicerConfigPlugin()

SlicerConfig.cmake provides the SlicerConfigPlugin macro to:

* FATAL_ERROR if languages are already enabled and tell the
  plugin author to add NONE to the project command

* Get the extension name from PROJECT_NAME, or alternatively
  from an optional explicit argument

* Set OS X platform variables and call enable_language()

Larger projects that provide a Slicer plugin along with a bunch
of other unrelated stuff will not want Slicer to control their
enable_language calls.  Therefore SlicerConfig should add another
macro (or options to this one) to just check that an already
enabled language has a matching platform selection and skip its
enable_language calls.

>    find_package(Slicer COMPONENTS ConfigurationPrerequisites)
>    project(Foo)
>    find_package(A ..)
>    find_package(B ..)
>
>   Can I be sure that the first call to "find_package" will be
>   done before language feature are enabled ?

Yes, but the above method may be even simpler.