# ECMGeneratePriFile

Generate a `.pri` file for the benefit of qmake-based projects.

As well as the function below, this module creates the cache variable `ECM_MKSPECS_INSTALL_DIR` and sets the default value to `mkspecs/modules`. This assumes Qt and the current project are both installed to the same non-system prefix. Packagers who use `-DCMAKE_INSTALL_PREFIX=/usr` will certainly want to set `ECM_MKSPECS_INSTALL_DIR` to something like `share/qt5/mkspecs/modules`.

The main thing is that this should be the `modules` subdirectory of either the default qmake `mkspecs` directory or of a directory that will be in the `$QMAKEPATH` environment variable when qmake is run.

    ecm_generate_pri_file(BASE_NAME <baseName>
                          LIB_NAME <libName>
                          [VERSION <version>] # since 5.83
                          [DEPS "<dep> [<dep> [...]]"]
                          [FILENAME_VAR <filename_variable>]
                          [INCLUDE_INSTALL_DIRS <dir> [<dir> [...]]]  # since 5.92
                          [INCLUDE_INSTALL_DIR <dir>] # deprecated since 5.92
                          [LIB_INSTALL_DIR <dir>])

If your CMake project produces a Qt-based library, you may expect there to be applications that wish to use it that use a qmake-based build system, rather than a CMake-based one. Creating a `.pri` file will make use of your library convenient for them, in much the same way that CMake config files make things convenient for CMake-based applications. `ecm_generate_pri_file()` generates just such a file.

`VERSION` specifies the version of the library the `.pri` file describes. If not set, the value is taken from the context variable `PROJECT_VERSION`. This variable is usually set by the `project(... VERSION ...)` command or, if CMake policy CMP0048 is not `NEW`, by `ECMSetupVersion`. For backward-compatibility with older ECM versions the `PROJECT_VERSION_STRING` variable as set by `ECMSetupVersion` will be preferred over `PROJECT_VERSION` if set, unless the minimum required version of ECM is 5.83 and newer. Since 5.83.

`BASE_NAME` specifies the name qmake project (.pro) files should use to refer to the library (eg: KArchive). `LIB_NAME` is the name of the actual library to link to (ie: the first argument to add_library()). `DEPS` is a space-separated list of the base names of other libraries (for Qt libraries, use the same names you use with the `QT` variable in a qmake project file, such as “core” for QtCore). `FILENAME_VAR` specifies the name of a variable to store the path to the generated file in.

`INCLUDE_INSTALL_DIRS` are the paths (relative to `CMAKE_INSTALL_PREFIX`) that include files will be installed to. It defaults to `${INCLUDE_INSTALL_DIR}/<baseName>` if the `INCLUDE_INSTALL_DIR` variable is set. If that variable is not set, the `CMAKE_INSTALL_INCLUDEDIR` variable is used instead, and if neither are set `include` is used. `LIB_INSTALL_DIR` operates similarly for the installation location for libraries; it defaults to `${LIB_INSTALL_DIR}`, `${CMAKE_INSTALL_LIBDIR}` or `lib`, in that order.

`INCLUDE_INSTALL_DIR` is the old variant of `INCLUDE_INSTALL_DIRS`, taking only one directory.

Example usage:

    ecm_generate_pri_file(
        BASE_NAME KArchive
        LIB_NAME KF5KArchive
        DEPS "core"
        FILENAME_VAR pri_filename
        VERSION 4.2.0
    )
    install(FILES ${pri_filename} DESTINATION ${ECM_MKSPECS_INSTALL_DIR})

A qmake-based project that wished to use this would then do:

    QT += KArchive

in their `.pro` file.

Since pre-1.0.0.