I have an itch to scratch...

[Peter Wainwright]

Functionally, DDD is the best debugger I've ever used (at least, on
a Free Software platform). Over the past 5 years it has become an
indispensable part of my programming toolkit.

However, visually, it is as UGLY as SIN. Clearly, Motif was an
obvious choice of toolkit when DDD was first conceived, but now
it sticks out like a sore thumb on modern Linux systems, with
their anti-aliased fonts and desktop themes. So, in response
to my itch (also popular demand) I've embarked on the process of
porting DDD to Gtk - or more precisely the C++ binding thereof,
Gtkmm. I notice this question comes up from time to time on the
mailing list, but it is a daunting prospect and no-one seems to
have grasped the nettle yet. Since I have some experience of both
Motif and Gtk, and have ported a small application between these in
the past, I felt obliged to give it a try (OK, that itch is
infuriating).

This work is at a very preliminary stage - I haven't even got the
first version to compile yet. However, some code will be available
soon, I promise ;-)

I'm not underestimating the difficulty of this task. At the moment,
I am just running through the code, porting the obvious stuff and
deferring the tricky (and less important) stuff until I have a working
demo. The final code should have a compile-time switch which will
revert to a full-featured Motif version. The approach I am taking is
this:
(1) Use a compile-time preprocessor macro, IF_MOTIF.
(2) Comment out all the Motif, Xt Intrinsics and standard X11
    include directives thus:
   #ifdef IF_MOTIF
   #include <Xm/...>
   ...
   #endif // IF_MOTIF
(3) Try to compile - of course the code breaks.
(4) Step through the errors: these are all the Xm, Xt and standard
    X calls; fix each of these in turn (a long job, still ongoing).
(5) All files which included <X11/*>, <Xm/*> now also include asince t
    "gtk_wrapper.h". This is an abstraction layer. This contains
    a big preprocessor conditional
   #ifdef IF_MOTIF
   ...
   #else
   ...
   #endif // IF_MOTIF
(6) In some cases the equivalences are easily dealt with in the short
    term by typedefs or macros, where there is a 1-1 correspondence
between
    the concepts in Motif and Gtkmm:
    typedef Gtk::Widget *Widget;
    #define XtPopdown(w) (w)->hide()
(7) In other cases I have put #ifdef...#else...#endif conditionals. When
we
    have created a prototype we can go back and look though these to
    identify the requirements for a portability layer. I hope that in
future
    this could accommodate QT as well (although I have no experience of
QT
    programming). There are a a very limited number of Motif idioms in
    DDD, which gives me some hope that the task is not impossible. The
main
    difference is the XtCallback mechanism versus the signal-slot stuff,
    but there is a natural mapping for most of this.
    My own feeling is that the most elegant solution would be to wrap
the
    required parts of Motif (not all of it) in an object-oriented layer
like
    Gtkmm, with constructors/destructors and a signal-slot paradigm as
provided
    by libsigc++. The result would look a lot more like pure Gtkmm but
would
    still provide Motif as an alternative backend (Xmmm, perhaps?).

I'm still looking at this and hope to post some sample code in the next
few
months.

Regards,

Peter

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