[CMake] Externally hooking a FindXYZ module

[Yuri V. Timenkov]

On Monday 25 August 2008 23:07:28 Fernando Cacciola wrote:
> Hi people,
>
> It turns out that Mac's Leopard OS needs a fix for OpenGL. The fix
> itself  has been discussed in this list a while back:
>
> http://www.mail-archive.com/cmake@cmake.org/msg09358.html
>
>
> I need to incorporate that fix into production code, and I don't want to
> distribute my own hacked up version FindOpenGL.cmake, not a real one at
> least, so I wonder, is there a way to hook into the find_package behaviour?
>
>
> The only hack I could come up was stubbing a Find module
> in this way:
>
> (1)
> At the most top level CMakeLists.txt:
>
> # Save aside the default modules path.
> set(ORIGINAL_CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} )
>
> # Prepend a project specific path so my modules take precedence
> set(CMAKE_MODULE_PATH "cmake_modules" ${CMAKE_MODULE_PATH} )
>
>
>
> (2)
> Then at the local cmake_modules folder, add a "FindOpenGL.cmake" stub
> with this:
>
>
> # Avoid recursion
> if ( NOT FIND_OPENGL_WRAPPER )
>
>    set ( FIND_OPENGL_WRAPPER 1 )
>
>    set(SAVED_CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} )
>
>    set(CMAKE_MODULE_PATH ${ORIGINAL_CMAKE_MODULE_PATH} )
>
>    # This calls the real module.
>    find_package(OpenGL)
>
>    # Here is the post-processing to "fix" OpenGL for leopard
>
>    if ( OPENGL_FOUND AND APPLE_LEOPARD )
>
>      set (CMAKE_SHARED_LINKER_FLAGS "-Wl,-dylib_file,/System/
> Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib:/
> System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib
>")
>
>    endif()
>
>    # reset the modules path.
>    set(CMAKE_MODULE_PATH ${SAVED_CMAKE_MODULE_PATH} )
>
> endif()
>
>
> Is there a better way??
First, you can move linking flags logic outside of FindGL.cmake file, therefore 
you don't need customization.

Alternatively you can copy this file to your custom modules directory and do 
not call original one.

>
> TIA
>
> Fernando Cacciola
>
>
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