Fix domain detection when rendering groups.

[rkapl]

Groups themselves do not have any filenames, so the detection must be
done on lower level. However, compound signatures were rendered in the
context of the group, with the default domain (C++) . This lead to all kinds of
missed reference from C domain code.

For example, let's have in test.h:
/** @ingroup test */ typedef struct {} example_t;
and /** @ingroup test */ void user(example_t arg);

Breathe is configured to recognize .h files as C domain. If you use doxygenfile, the links work correctly. If you use doxygengroup, the the arguments of the user function are not links and example_t is in the C++ domain.

[vermeeren]

Hi, sorry for the wait. The changes look good to me, but I can't test an example locally.

I created a .h file in a project:

#pragma once

/** @ingroup test */
typedef struct
{
} example_t;

/** @ingroup test */
void user(example_t arg);

But get:

WARNING: doxygengroup: Cannot find namespace "test" in doxygen xml output for project "__PROJECT_NAME__" from directory: /.../build/tmp/doc/doxygen/xml

Checking the generated XML the word test is nowhere to be found. Is there something that should be enabled in Doxyfile for this to work?

[rkapl]

Sorry, please also add /** @defgroup test */. To the example file.

[vermeeren]

Thanks for the quick reply.

Just to make sure I get it properly, the only difference is that in void user(example_t arg) the example_t type is now in the correct domain and thus a link, right?

[rkapl]

Yes, the point was to make these links work. Maybe it also affects something else, but I don't know.

[vermeeren]

Merged, thank you for the PR.