Re: debugging emacs

[Richard Stallman]

    pre-processor stuff, c and lisp did the trick. it feels more like
    debugging a closed source binary thing I did in past.

If you use the term "closed source" when discussing Emacs, you're
likely to give people the wrong idea--they may think our work is
associated with what some call "open source".  That is unfortunate,
because we have nothing to do with either one.  What we have been
doing, since 1984, is called "free software".

The term "open source" was coined in 1998 by a group of people
that disagreed with our philosophy.  They have a right to promote
their views, but please don't lump us in with them.

See http://www.gnu.org/philosophy/free-software-for-freedom.html for
more explanation.

    now I can press any key, and it will cause both frames to unhighlight the
    text. [THIS is the code chain I look : from pressing a key until the
    text gets unhighligted]

That sounds like the intended behavior to me.  The highlighting that
results from selecting a region with the mouse does not last past the
next command.

If you want highlighting to last as long as the region lasts, you can
enable Transient Mark mode.