[CMake] Using Qt5 with CMake

[Stephen Kelly]

Alan W. Irwin wrote:

> (1) How should you replace
> 
> find_package(Qt4 4.8.2 COMPONENTS QtCore QtGui QtSvg)

 find_package(Qt5 5.2.1 COMPONENTS Svg)

or 

 find_package(Qt5Svg 5.2.1)

Packages and targets know their dependencies so you don't have to.

> and
> 
> qt4_wrap_cpp(
>    QT_MOC_OUTFILES
>    ${CMAKE_SOURCE_DIR}/include/qt.h
>    OPTIONS ${MOC_OPTIONS}
>    )

qt5_wrap_cpp(
   QT_MOC_OUTFILES
   ${CMAKE_SOURCE_DIR}/include/qt.h
   OPTIONS ${MOC_OPTIONS}
   )

Though you can port to AUTOMOC before/after porting to Qt 5 too.

> Does Qt5
> still use that directory property apprach for setting compile flags
> or is this no longer an issue?

Qt 5 provides IMPORTED targets which have the compile flags encoded in them. 
The flags are consumed by target_link_libraries.

 http://www.cmake.org/cmake/help/v3.0/manual/cmake-buildsystem.7.html

 target_link_libraries(foo Qt5::Svg)

Qt4 provides IMPORTED targets too, so you can already use those before 
porting to Qt 5 instead of whatever mechanism you currently use.

 target_link_libraries(foo Qt4::QtSvg)

 http://www.cmake.org/cmake/help/v3.0/manual/cmake-qt.7.html

> target_link_libraries(
>    plplotqt${LIB_TAG}
>    plplot${LIB_TAG}
>    ${MATH_LIB}
>    ${QT_LIBRARIES}
>    )
> 
> How should that command be replaced for the new Qt5 way of doing
> things?

I recommend listing the IMPORTED target 'leaf' dependencies.

target_link_libraries(
   plplotqt${LIB_TAG}
   plplot${LIB_TAG}
   ${MATH_LIB}
   Qt4::QtSvg
   # Qt5::Svg
   )

You can use 

 set(QT_LIBRARIES Qt4::QtSvg)

either, but I recommend using the target names directly.

Thanks,

Steve.