How To Build KDE4 Software

A simple example

Let's just start with a simple example for an application, let's name it, well, ksimple. The CMakeLists.txt below gives the project a name, so that the project files for KDevelop/XCode/MSVC will have a good name. It will then find the KDE 4 installation on the system and setup the required include directories. The list of source files will be put into a variable named mySources, which will be automoced and then used to build an executable from it. The executable and its desktop file will finally be installed.

project(ksimple)

find_package(KDE4 REQUIRED)

include_directories( ${KDE4_INCLUDES} )

set(mySources main.cpp mywidget.cpp mypart.cpp)

kde4_automoc( ${mySources} )

kde4_add_executable(ksimple ${mySources})

target_link_libraries(ksimple ${KDE4_KDEUI_LIBS} ${KDE4_KPARTS_LIBS} )

install(TARGETS ksimple DESTINATION bin)
install(FILES kfoo.desktop DESTINATION ${XDG_APPS_DIR})

A full-featured example

Ok, and now for a full-featured but non-working example.

Give the project a name, find KDE 4 and setup CMAKE_MODULE_PATH. This has the effect that cmake will also use check the ${CMAKE_SOURCE_DIR}/cmake directory for files if you use include(somefile) or find_package(something). Please note that this directory is added to the former contents of CMAKE_MODULE_PATH. This is important, since if find_package(KDE4) was successfully, it will have setup CMAKE_MODULE_PATH so that it points to the directory where the cmake files installed with kdelibs are located.

project(kfoo)

find_package(KDE4 REQUIRED)

set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})

Then apply the required settings:

include_directories( ${KDE4_INCLUDE_DIRS})
add_definitions( ${KDE4_DEFINITIONS} )

Create a variable which holds your source files:

set(kfooSources main.cpp myappl.cpp view.cpp)

If you have Qt designer ui files version 3 or 4 add them to the variable we just created:

kde4_add_ui_files( kfooSources maindialog.ui logindialog.ui)

kde4_add_ui3_files( kfooSources printerdlg.ui previewdlg.ui)

If you have files for the kconfig_compiler add them this way:

kde4_add_kcfg_files( kfooSources settings.kcfg )

You have some DBUS stuff too ? ...not done yet...

So, if you have listed everything, you probably want automoc:

kde4_automoc( ${kfooSources} )

Please note that kde4_automoc() doesn't take the name of a variable as argument, but just a list of files. That's why kfooSource is "dereferenced" here.

Finally, tell cmake what you want to build:

kde4_add_executable(kfoo ${kfooSources} )

This is a slightly extended version of the original CMake add_executable(). Additionally it does some more RPATH handling and supports KDE4_ENABLE_FINAL. Just as add_executable() the first argument is the name of the executable followed by the list of source files. If you want to create a library instead of an executable, it works similar:

kde4_add_library(kfoo ${kfooSources} )
set_target_properties( kfoo PROPERTIES VERSION 5.0.0 SOVERSION 5 )

As above with add_executable(), kde4_add_library() is an extended version of the add_library() command. It adds support for KDE4_ENABLE_FINAL and under windows it adds "-DMAKE_KFOO_LIB" to the compile flags. The set_target_properties() command is optional, if you don't need a version number for the library you can just skip it.

KDE is very modular, so if you want to create a KPart, or a control center module, or an ioslave, here's how to do it:

kde4_add_plugin( kfoo ${kfooSources} )

Now your application/library/plugin probably needs to link to some libraries. For this use the standard cmake target_link_libraries() command. For every KDE library there are variables in the form "KDE4_FOO_LIBS" available. Use them and you get also all depending libraries:

target_link_libraries( kfoo ${KDE4_KDEUI_LIBS} ${KDE4_KIO_LIBS})

And now some words about kdeinit-executables. They can also be created with cmake. Here's an example:

kde4_add_kdeinit_executable(kbar ${kbarSources} )
target_link_libraries(kdeinit_kbar ${KDE4_KIO_LIBS} )
target_link_libraries( kbar kdeinit_kbar)

install(TARGETS kbar DESTINATION ${BIN_INSTALLDIR})
install(TARGETS kdeinit_kbar DESTINATION ${LIB_INSTALL_DIR})

As you can see, here's a bit more going on. kde4_add_kdeinit_executable() creates both an executable with the given name and a library with the given name prefixed with "kdeinit_". Use target_link_libraries() to add all required libraries to the kdeinit_kbar library, and then link kbar against kdeinit_kbar.

In the examples above the install commands are missing. The KDE 4 support in cmake provides a bunch of predefined variables you should use, e.g. if it's a library:

install(TARGETS kfoo DESTINATION ${LIB_INSTALL_DIR})

There is also PLUGIN_INSTALL_DIR and a bunch more variables, see the top of FindKDE4Internal.cmake for details.

Some useful functions

Sometimes, you can want to remove a default argument passed to the compiler, then the remove_definitions is for you. For example, by default, the KDE4 build system sets the -DQT_NO_STL flag. If your code uses some of the Qt STL compatibility layer, you will want to remove this flag. Simply do:

remove_definitions(-DQT_NO_STL)

Where to find more information

The KDE 4 support of cmake consists of the file FindKDE4.cmake, which comes with cmake and is mainly a forwarder to the file FindKDE4Internal.cmake. In FindKDE4Internal.cmake system-dependent settings are set and the KDE libraries, executables and include directories reqauired for building KDE 4 software are searched. Additionally to FindKDE4Internal.cmake there are the files KDE4Macros.cmake. This file implements all the KDE4-specific commands we used above. If you do

find_package(KDE4)

these macros are automatically available to you. There is also a file KDE4Defaults.cmake which sets some minor cmake options which are good, but not absolutely required for building KDE 4 software. If you want to use these settings, include this file:

include(KDE4Defaults)

These three files come with the KDE libraries and are installed to share/apps/cmake/modules/. If you want to know more details, it is always a good idea to have a look at these files directly.

At the top of FindKDE4Internal.cmake you can find the complete documentation for all variables and macros these files provide.

This page was initially populated by conversion from its original location in another wiki.