FindQt4.cmake synced with the version from cmake

[Alexander Neundorf]

On Tuesday 22 December 2009, Thiago Macieira wrote:
> Em Terça-feira 22. Dezembro 2009, às 10.20.59, Mike Arthur escreveu:
> > On 22 Dec 2009, at 11:36, Thiago Macieira wrote:
> > > Yeah, that's what you said before.
> > >
> > > But my question is: if I want to link to a given libfoo, how do I know
> > > if it should be LIBRARY or LIBRARIES? Do I have to look into the
> > > documentation of the module, or is there a convention I can use to
> > > guess?

Yes, it should be in the documentation.
And that documentation should say that you should use the xxx_LIBRARIES 
variable, and I think that's also the case for the majority of the modules.

> > You don't. This depends on the Find*.cmake module. Preempting your
> >  response, I agree this is pretty stupid.

Well, it may be stupid, but at least as long as it is documented, it's not a 
bug. Basically this depends on the authors of the find-modules.

> > > What happens if there's a technical change that requires now two
> > > libraries (like the Mac case)?
> >
> > Well, it'll still work unless you have it quoted, like the above example,
> >  because then it will break the list of two libraries into a single
> > library with a space in the path.
>
> Can we then change the convention to use LIBRARIES, always, for all types
> of libraries?


From cmake/Modules/readme.txt:

XXX_LIBRARIES          	The libraries to link against to use XXX. These should 
include full paths.  This should not be a cache entry.
...
XXX_LIBRARY		Name of XXX Library. A User may set this and XXX_INCLUDE_DIR to 
ignore to force non-use of XXX.

So yes, we should use the LIBRARIES/LIBS variables.
There are also the QT_QTxxx_LIBRARIES variables.

Beside that, we can also make the new (for us) code in FindQt4.cmake handle 
this differently.
Right now it does:

  IF (CMAKE_CONFIGURATION_TYPES OR CMAKE_BUILD_TYPE)
    SET(QT_${basename}_LIBRARY optimized ${QT_${basename}_LIBRARY_RELEASE} 
                               debug ${QT_${basename}_LIBRARY_DEBUG})
  ELSE(CMAKE_CONFIGURATION_TYPES OR CMAKE_BUILD_TYPE)
    # if there are no configuration types and CMAKE_BUILD_TYPE has no value
    # then just use the release libraries
    SET(QT_${basename}_LIBRARY       ${QT_${basename}_LIBRARY_RELEASE} )
  ENDIF(CMAKE_CONFIGURATION_TYPES OR CMAKE_BUILD_TYPE)
  SET(QT_${basename}_LIBRARIES  optimized ${QT_${basename}_LIBRARY_RELEASE} 
                                debug ${QT_${basename}_LIBRARY_DEBUG})
ENDIF (QT_${basename}_LIBRARY_DEBUG AND QT_${basename}_LIBRARY_RELEASE)


I guess it would make sense to do this only if actually both versions have 
been found. Also CMAKE_CONFIGURATION_TYPES and CMAKE_BUILD_TYPE could be 
handled separately (set it to only one of the libs when CMAKE_BUILD_TYPE is 
used, i.e. in makefiles, and ... not quite sure about the best way how to 
handle CMAKE_CONFIGURATION_TYPES).

(nobody among the cmake developers is happy about the way 
the "optimized/debug" feature is implemented, but it is there, so it has to 
stay)

Alex