[CMake] QT_DEFINITIONS

[Clinton Stimpson]

On Sunday, May 23, 2010 08:26:42 am Michael Hertling wrote:
> Dear CMake community,
> 
> after having taken a look into FindQt4.cmake, UseQt4.cmake and
> Qt4ConfigDependentSettings.cmake, I wonder how the QT_DEFINITIONS
> variable gets populated. As far as I can see, this variable remains
> empty, perhaps except for -DQT_DLL on Windows; in particular, it does
> not receive the -DQT_<library>_LIB flags which are solely enabled via
> ADD_DEFINITIONS() by UseQt4.cmake, i.e. with INCLUDE(${QT_USE_FILE})
> as suggested by FindQt4.cmake. Of course, from within a FindXXX.cmake
> or XXXConfig.cmake for a package depending on Qt4, one does not want
> to have the build environment modified by ADD_DEFINITIONS() et al.,
> but convey the necessary settings by variables like QT_DEFINITIONS.
> Therefore, my question is how to get to know about the flags for
> compiling Qt4-dependent packages without including UseQt4.cmake.
> 
> BTW, what is the recommendation for a package XXX which depends on a
> package YYY regarding FindXXX.cmake and FindYYY.cmake, i.e. would one
> expect FindXXX.cmake to call FIND_PACKAGE(YYY), or is the user expected
> to call FIND_PACKAGE() for XXX and YYY in the correct order and, as the
> case may be, with sufficient sets of components? In general, the latter
> is easier for the finders, but the former would be more convenient for
> the user.
> 
> Any comments, suggestions etc. would be greatly appreciated.

I think the answer depends on whether the user of your software will be 
writing Qt based code themselves, or whether Qt is hidden behind your apis.
If they write Qt code themselves, they could choose to use a different set of 
Qt modules, in which case compile flags could change.

Clint