The creation of the doxygen documentation is turned off by default -- the recreation at every new compilation takes too much time in the usual development. A switch need to be present for the cmake command, the variable

INSTALL_DOC

is by default NO. Use the -D option while invoking the cmake command to set it differently. In the usual invocation of cmake in the build directory (with your appropriate ILCSoft.cmake file) this will look like

cmake -C ${YOUR_ILCSOFT_CMAKE} -D INSTALL_DOC=YES ..

Now invoke

make doc

and the doxygen documentation will be generated in the ./doc directory of the project directory.

Use any html browser to take a look at it, starting with

doc/html/index.html