[KPhotoAlbum] CMakeLists.txt and libkface

[Tobias Leupold]

Hi list!

I recently had a small conversation with the Gentoo guys maintaining the KPA 
ebuilds about how to handle optional dependencies like libkface. Currently, 
this is the way we search for it (added by Pino Toscano):

	find_package(Kface 3.5.0 CONFIG)
	set(KFACE_FOUND ${Kface_FOUND})
	if(KFACE_FOUND)
	    set(KFACE_LIBRARIES ${Kface_LIBRARIES})
	    INCLUDE_DIRECTORIES(${Kface_INCLUDE_DIR})
	else()
	    unset(KFACE_FOUND)
	    pkg_check_modules(KFACE libkface>=3.5.0)
	    if(KFACE_FOUND)
	        INCLUDE_DIRECTORIES(${KFACE_INCLUDE_DIR})
	    endif()
	endif(KFACE_FOUND)
	macro_bool_to_01(KFACE_FOUND HAVE_KFACE)

This includes a "fallback" search if no cmake module for libkface is found. 
But it also (apparently, I'm not a cmake pro ;-) makes it hard to skip the 
libkface inclusion if the library is present, but should not be used to build 
KPA.

Michael Palimaka from Gentoo said that if it's possible, we should use 
find_package. It's true that older versions of libkface do not ship a cmake 
module. But we need at least libkface 3.5.0 (currently only available from git 
master), which comes with a cmake module. So if we have some libkface version 
installed without it, it's too old anyway, so I think we don't need this 
fallback check.

So I tried it with:

	find_package(Kface 3.5.0 CONFIG)
	macro_bool_to_01(KFACE_FOUND HAVE_KFACE)
	if(KFACE_FOUND)
	    INCLUDE_DIRECTORIES(${KFACE_INCLUDE_DIR})
	endif(KFACE_FOUND)

which works just fine here, with and without libkface, and will also play nice 
with Portage and USE flags on Gentoo. Would you please verify that this is 
also okay on other systems?

Thanks in advance!

Cheers, Tobias