Encapsulate log interface selection

[elfring]

Conditional compilation was introduced for a possible logging software.
This software adjustment had the consequence that preprocessor statements were distributed in the code base.
Thus I suggest to reduce unwanted code duplication.

• Dedicated macros can help.
• Will advanced class templates become safer for this use case?

[aesophor]

Previously:

#if GLOG_FOUND != FALSE
    LOG(INFO) << "Failed to open display to X server.";
#endif

With the help of this macro, it can be written in one line now.

WM_LOG(INFO, "Failed to open display to X server.");

If glog is not installed, then this macro will be expanded into an empty statement instead.

[elfring]

Thanks for another software improvement.
I am curious if these logging interfaces will evolve any further.

[aesophor]

• Will advanced class templates become safer for this use case?

You have mentioned templates, do you mean something like: WM_LOG<INFO>("Some cool messages")

I guess this will need a dedicated templated function and template specialization.

[elfring]

Do you get any further development ideas from a library like spdlog?