# ECMAddQch

This module provides the `ecm_add_qch` function for generating API documentation files in the QCH format, and the `ecm_install_qch_export` function for generating and installing exported CMake targets for such generated QCH files to enable builds of other software with generation of QCH files to create links into the given QCH files.

    ecm_add_qch(<target_name>
        NAME <name>
        VERSION <version>
        QCH_INSTALL_DESTINATION <qchfile_install_path>
        TAGFILE_INSTALL_DESTINATION <tagsfile_install_path>
        [COMPONENT <component>]
        [BASE_NAME <basename>]
        [SOURCE_DIRS <dir> [<dir2> [...]]]
        [SOURCES <file> [<file2> [...]]]
        |MD_MAINPAGE <md_file>]
        [INCLUDE_DIRS <incdir> [<incdir2> [...]]]
        [IMAGE_DIRS <idir> [<idir2> [...]]]
        [EXAMPLE_DIRS <edir> [<edir2> [...]]]
        [ORG_DOMAIN <domain>]
        [NAMESPACE <namespace>]
        [LINK_QCHS <qch> [<qch2> [...]]]
        [PREDEFINED_MACROS <macro[=content]> [<macro2[=content]> [...]]]
        [BLANK_MACROS <macro> [<macro2> [...]]]
        [CONFIG_TEMPLATE <configtemplate_file>]
        [VERBOSE]
    )

This macro adds a target called <target_name> for the creation of an API documentation manual in the QCH format from the given sources. It currently uses doxygen, future versions might optionally also allow other tools. Next to the QCH file the target will generate a corresponding doxygen tag file, which enables creating links from other documentation into the generated QCH file.

It is recommended to make the use of this macro optional, by depending the call to `ecm_add_qch` on a CMake option being set, with a name like `BUILD_QCH` and being `TRUE` by default. This will allow the developers to saves resources on normal source development build cycles by setting this option to FALSE.

The macro will set the target properties `DOXYGEN_TAGFILE`, `QHP_NAMESPACE`, `QHP_NAMESPACE_VERSIONED`, `QHP_VIRTUALFOLDER` and `LINK_QCHS` to the respective values, to allow other code access to them, e.g. the macro `ecm_install_qch_export`. To enable the use of the target <target_name> as item for `LINK_QCHS` in further `ecm_add_qch` calls in the current build, additionally a target property `DOXYGEN_TAGFILE_BUILD` is set, with the path of the created doxygen tag file in the build dir. If existing, `ecm_add_qch` will use this property instead of `DOXYGEN_TAGFILE` for access to the tags file.

`NAME` specifies the name for the generated documentation.

`VERSION` specifies the version of the library for which the documentation is created.

`BASE_NAME` specifies the base name for the generated files. The default basename is `<name>`.

`SOURCE_DIRS` specifies the dirs (incl. subdirs) with the source files for which the API documentation should be generated. Dirs can be relative to the current source dir. Dependencies to the files in the dirs are not tracked currently, other than with the `SOURCES` argument. So do not use for sources generated during the build. Needs to be used when `SOURCES` or `CONFIG_TEMPLATE` are not used.

`SOURCES` specifies the source files for which the API documentation should be generated. Needs to be used when `SOURCE_DIRS` or `CONFIG_TEMPLATE` are not used.

`MD_MAINPAGE` specifies a file in Markdown format that should be used as main page. This page will overrule any `\mainpage` command in the included sources.

`INCLUDE_DIRS` specifies the dirs which should be searched for included headers. Dirs can be relative to the current source dir. Since 5.63.

`IMAGE_DIRS` specifies the dirs which contain images that are included in the documentation. Dirs can be relative to the current source dir.

`EXAMPLE_DIRS` specifies the dirs which contain examples that are included in the documentation. Dirs can be relative to the current source dir.

`QCH_INSTALL_DESTINATION` specifies where the generated QCH file will be installed.

`TAGFILE_INSTALL_DESTINATION` specifies where the generated tag file will be installed.

`COMPONENT` specifies the installation component name with which the install rules for the generated QCH file and tag file are associated.

`NAMESPACE` can be used to set a custom namespace <namespace> of the generated QCH file. The namepspace is used as the unique id by QHelpEngine (cmp. https://doc.qt.io/qt-5/qthelpproject.html#namespace). The default namespace is `<domain>.<name>`. Needs to be used when `ORG_DOMAIN` is not used.

`ORG_DOMAIN` can be used to define the organization domain prefix for the default namespace of the generated QCH file. Needs to be used when `NAMESPACE` is not used.

`LINK_QCHS` specifies a list of other QCH targets which should be used for creating references to API documentation of code in external libraries. For each target <qch> in the list these target properties are expected to be defined: `DOXYGEN_TAGFILE`, `QHP_NAMESPACE` and `QHP_VIRTUALFOLDER`. If any of these is not existing, <qch> will be ignored. Use the macro `ecm_install_qch_export` for exporting a target with these properties with the CMake config of a library. Any target <qch> can also be one created before in the same buildsystem by another call of `ecm_add_qch`.

`PREDEFINED_MACROS` specifies a list of C/C++ macros which should be handled as given by the API dox generation tool. Examples are macros only defined in generated files, so whose definition might be not available to the tool.

`BLANK_MACROS` specifies a list of C/C++ macro names which should be ignored by the API dox generation tool and handled as if they resolve to empty strings. Examples are export macros only defined in generated files, so whose definition might be not available to the tool.

`CONFIG_TEMPLATE` specifies a custom cmake template file for the config file that is created to control the execution of the API dox generation tool. The following CMake variables need to be used: - `ECM_QCH_DOXYGEN_QHELPGENERATOR_EXECUTABLE` - `ECM_QCH_DOXYGEN_FILEPATH, ECM_QCH_DOXYGEN_TAGFILE` The following CMake variables can be used: - `ECM_QCH_DOXYGEN_PROJECTNAME` - `ECM_QCH_DOXYGEN_PROJECTVERSION` - `ECM_QCH_DOXYGEN_VIRTUALFOLDER` - `ECM_QCH_DOXYGEN_FULLNAMESPACE` - `ECM_QCH_DOXYGEN_TAGFILES` - `ECM_QCH_DOXYGEN_WARN_LOGFILE` - `ECM_QCH_DOXYGEN_QUIET` There is no guarantue that the other CMake variables currently used in the default config file template will also be present with the same semantics in future versions of this macro.

`VERBOSE` tells the API dox generation tool to be more verbose about its activity.

The default config file for the API dox generation tool, so the one when not using `CONFIG_TEMPLATE`, allows code to handle the case of being processed by the tool by defining the C/C++ preprocessor macro `K_DOXYGEN` when run (since v5.67.0). For backward-compatibility also the definition `DOXYGEN_SHOULD_SKIP_THIS` is set, but its usage is deprecated.

Example usage:

    ecm_add_qch(
        MyLib_QCH
        NAME MyLib
        VERSION "0.42.0"
        ORG_DOMAIN org.myorg
        SOURCE_DIRS
            src
        LINK_QCHS
            Qt5Core_QCH
            Qt5Xml_QCH
            Qt5Gui_QCH
            Qt5Widgets_QCH
        BLANK_MACROS
            MyLib_EXPORT
            MyLib_DEPRECATED
        TAGFILE_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/tags
        QCH_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/qch
        COMPONENT Devel
    )

Example usage (with two QCH files, second linking first):

    ecm_add_qch(
        MyLib_QCH
        NAME MyLib
        VERSION ${MyLib_VERSION}
        ORG_DOMAIN org.myorg
        SOURCES ${MyLib_PUBLIC_HEADERS}
        MD_MAINPAGE src/mylib/README.md
        LINK_QCHS Qt5Core_QCH
        TAGFILE_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/tags
        QCH_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/qch
        COMPONENT Devel
    )
    ecm_add_qch(
        MyOtherLib_QCH
        NAME MyOtherLib
        VERSION ${MyOtherLib_VERSION}
        ORG_DOMAIN org.myorg
        SOURCES ${MyOtherLib_PUBLIC_HEADERS}
        MD_MAINPAGE src/myotherlib/README.md
        LINK_QCHS Qt5Core_QCH MyLib_QCH
        TAGFILE_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/tags
        QCH_INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/share/docs/qch
        COMPONENT Devel
    )

    ecm_install_qch_export(
        TARGETS [<name> [<name2> [...]]]
        FILE <file>
        DESTINATION <dest>
        [COMPONENT <component>]
    )

This macro creates and installs a CMake file <file> which exports the given QCH targets <name> etc., so they can be picked up by CMake-based builds of other software that also generate QCH files (using `ecm_add_qch`) and which should include links to the QCH files created by the given targets. The installed CMake file <file> is expected to be included by the CMake config file created for the software the related QCH files are documenting.

`TARGETS` specifies the QCH targets which should be exported. If a target does not exist or does not have all needed properties, a warning will be generated and the target skipped. This behaviour might change in future versions to result in a fail instead.

`FILE` specifies the name of the created CMake file, typically with a .cmake extension.

`DESTINATION` specifies the directory on disk to which the file will be installed. It usually is the same as the one where the CMake config files for this software are installed.

`COMPONENT` specifies the installation component name with which the install rule is associated.

Example usage:

    ecm_install_qch_export(
        TARGETS MyLib_QCH
        FILE MyLibQCHTargets.cmake
        DESTINATION "${CMAKE_INSTALL_PREFIX}/lib/cmake/MyLib"
        COMPONENT Devel
    )

Since 5.36.0.