[cmake-developers] QtAutogen suggestions

[Brad King]

On 11/25/2016 05:37 PM, Sebastian Holtermann wrote:
> There are some issues with QtAutogen that still bother me and
> that I would like to change.

Great!  We currently have no dedicated maintainer for it and I have
little understanding of the tools and use cases associated with it
myself.  It will be useful to have your help.

> 1) Most files get generated in
> ${CMAKE_CURRENT_BINARY_DIR}/${TARGETNAME}_automoc.dir
> 
> Is the ".dir" suffix neccessary? I think is should be removed.

That suffix is the convention used for all intermediate files
(e.g. object files) associated with a particular target of any kind.
The _automoc targets are simply following that convention, but there
is no strong reason this has to be the case for the generated sources.

> 2) Moc files that are manually included by a
> #include "moc_<basename>.cpp"
> statement get generated in ${CMAKE_CURRENT_BINARY_DIR}
> 
> A better solution would be to generate the moc_<basename>.cpp files in
> ${CMAKE_CURRENT_BINARY_DIR}/${TARGETNAME}_automoc/include.
> AUTOMOC then should automatically add that directory to the
> INCLUDE_DIRECTORIES of the origin target.

Yes, I think that has been discussed before but no one ever implemented it.

> 3) The mocs compilation file currently gets generated as
> ${CMAKE_CURRENT_BINARY_DIR}/${TARGETNAME}_automoc.cpp
> 
> The file could be generated as
> ${CMAKE_CURRENT_BINARY_DIR}/${TARGETNAME}_automoc/compilation.cpp

Okay.

> 4) AUTOMOC AUTOUIC and AUTORCC perform different independent tasks that
> in the current implementation get processed serially inside a single
> custom target named ${TARGETNAME}_automoc.
> 
> I think each of the three could be handled in an own target.

In VS IDE and Xcode each target becomes another user-visible entity so
we try to keep generated targets to a minimum.  IIRC in some cases we
even try to use a PRE_BUILD step in the VS targets to avoid an extra
target altogether.  The breakdown could be made generator-specific
to improve behavior on Ninja and Makefile generators.  In the case that
a common target is needed it could be renamed to `_autogen` instead.

Thanks,
-Brad