Enables generation of QCH files during a normal build,
for documenting the public API of a library.
These macros are especially done with release builds in mind,
so distributed packages (like from Linux distributions) can
include QCH files matching the version of the library and will be
also automatically updated on new versions of the libary.
Next to that these macros also support linking between different
QCH files, so a subclass from another library for which there also
is a QCH file installed will be linked to the entry in that other
This inter-QCH linking is especially useful for libraries extending Qt,
where many of the used types are from Qt libraries. The macros
come with the needed information for Qt libraries prepared, so the
used Qt libraries just need to be listed in the LINK_QCHS argument
by target names, like Qt5Core_QCH or Qt5Widgets_QCH.
This should be a nice supplement to online services like api.kde.org,
like Qt's own QCH files are to doc.qt.io,
While QCH files from an abstract POV could be seen similar to code libraries, being components with
links to lookup symbols/entries in other QCH files, so the rules and code should be done with similar concepts,
currently CMake's target system seems bound to executable code creation.
So things like "file(EXPORT ...)" could sadly not be reused, as custom targets are not supported with that. Thus a custom macro had to be created for now. Also could I not find a way to use namespaces like KF5::, for more consistent target naming.
The patch also adds two variables to KDEInstallDirs.cmake for
controlling where the QCH (and respective doxygen tag files) are
installed. The QTQCHDIR variant allows to install QCH files for
Qt-extending libraries into the same folder where Qt's own QCH
files are, so Qt Assistant & other QCH viewer pick up them automatically
to add them to the default help file collection.
The QCHDIR variant would provide a neutral, but central installation location.
Neutral, as it never "pollutes" the Qt system dirs with files possibly unrelated to
Qt-based development (e.g. when simply using qthelp tools for documentation),
and central, to help with finding available QCH files for manually adding/loading
them into a viewer, given there is no official way currently to register the availability of
QCH files on installing.
a) target system for exporting/importing done in a sane way? Better name pattern for the QCH targets than xxx_QCH (see the targets created for Qt, like Qt5Core_QCH)?
b) sharing metadata with kapidox
Initially I placed these macros into the kapidox module, as this seems the
logic place. And would match what kdoctools does for user manuals.
Just, that would create a build dependency on kapidox which complicates usage
a little. Having these macros in ECM delivers them with no extra effort
The data in metainfo.yaml is partially duplicated with the data feed into
the macros. How to deduplicate that is still open. Especially with the need
to not depend on external data sources like identify.kde.org.
- released current doxygen versions broken and miss to include some files with generated QCH (https://bugzilla.gnome.org/show_bug.cgi?id=773693), fixed only in doxygen development version, patched already in openSUSE Tumbleweed
- inter-QCH links do not work in KDevelop currently (see https://bugs.kde.org/show_bug.cgi?id=372747)
More details/background info at