How can I link correctly to QT4 libraries in CMake?

Question

So I'm trying to build a program which was originally made with a CMake instead of a .pro file. However, I cannot build it because there is something wrong with the libraries declaration. For example, the following won't work:

#include <QtGui/QApplication>

However, this works more or less, but not completely:

#include <qt4/QtGui/QApplication>

If I use the above, then I get a huge amount of errors because the compiler says that it cannot find the headers that other headers point to. The problem is the prefix of qt4. How can I link it correctly in the CMake file so every header can be found under qt4 without me needing to change the whole bunch of headers shipped with QT-SDK?

---

CMAKE FILE: (Source: http://code.metager.de/source/xref/kde/Support/polkit-qt-1/examples/CMakeLists.txt)

install(FILES org.qt.policykit.examples.policy DESTINATION ${SHARE_INSTALL_PREFIX}/polkit-1/actions/)

include_directories(
${CMAKE_CURRENT_SOURCE_DIR}
${CMAKE_CURRENT_BINARY_DIR}
${CMAKE_SOURCE_DIR}/gui
)

set(polkit_example_SRCS
main.cpp
PkExample.cpp
)

SET(polkit_example_RESOUCES
icons/icons.qrc
)

FIND_PACKAGE(Qt4 REQUIRED)

QT4_WRAP_CPP(polkit_example_MOC_SRCS
PkExample.h
)

QT4_WRAP_UI(polkit_example_UI_SRCS
PkExample.ui
)

QT4_ADD_RESOURCES (qtsourceview_RC_SRCS  ${polkit_example_RESOUCES})

add_executable(polkit-example
${polkit_example_SRCS}
${polkit_example_MOC_SRCS}
${polkit_example_UI_SRCS}
${qtsourceview_RC_SRCS}
)

target_link_libraries(polkit-example
${QT_QTCORE_LIBRARY}
${QT_QTGUI_LIBRARY}
polkit-qt-gui-1
polkit-qt-core-1
)

#--------Helper Application

# This macro is defined in FindPolkitQt.cmake
macro(dbus_add_activation_system_service _sources)
foreach (_i ${_sources})
    get_filename_component(_service_file ${_i} ABSOLUTE)
    string(REGEX REPLACE "\\.service.*$" ".service" _output_file ${_i})
    set(_target ${CMAKE_CURRENT_BINARY_DIR}/${_output_file})
    configure_file(${_service_file} ${_target})
    install(FILES ${_target} DESTINATION ${SHARE_INSTALL_PREFIX}/dbus-1/system-services )
    #install(FILES ${_target} DESTINATION ${_install_dir})
endforeach (_i ${ARGN})
endmacro(dbus_add_activation_system_service _sources)

set(polkit_example_helper_SRCS
PkExampleHelper.cpp
mainHelper.cpp
)

qt4_add_dbus_adaptor(polkit_example_helper_SRCS
org.qt.policykit.examples.xml
PkExampleHelper.h
PkExampleHelper
)

QT4_WRAP_CPP(polkit_example_helper_MOC_SRCS
PkExampleHelper.h
)

add_executable(polkit-example-helper
${polkit_example_helper_SRCS}
${polkit_example_helper_MOC_SRCS}
)

# see our helper is pretty small :D
target_link_libraries(polkit-example-helper
${QT_QTCORE_LIBRARY}
polkit-qt-core-1
)


dbus_add_activation_system_service(org.qt.policykit.examples.service.in)

install(FILES org.qt.policykit.examples.conf DESTINATION ${SYSCONF_INSTALL_DIR}/dbus-1/system.d)

Answer 1

From what I can tell you're close. After your FIND_PACKAGE(Qt4 REQUIRED) include the following line:

INCLUDE(${QT_USE_FILE})

As per the documentation

The file pointed to by QT_USE_FILE will set up your compile environment by adding include directories, preprocessor defines, and populate a QT_LIBRARIES variable containing all the Qt libraries and their dependencies.

So that should set up the proper paths for you.