Date: Thu, 23 Mar 2006 20:54:10 +1100
From: Erik de Castro Lopo <ocaml-erikd at mega-nerd.com>
To: lablgtk at math.nagoya-u.ac.jp
Subject: Request for advice (long)
Message-Id: <20060323205410.5bb789f8.ocaml-erikd at mega-nerd.com>
Organization: Erik Conspiracy Secret Labs
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Hi all,

Yesterday, I posted a very much cut down version of what I was
trying to achieve and Olivier Andrieu was kind enough to help
me over a couple of hurdles.

Unfortunately, it turns out that the cut down version of my 
problem actually didn't represent the problem very well, so
I'm back to ask for some further advice :-).

The project I'm working on is a graphical diff program. The
idea is to load up two sightly different versions of the same
source code file and have them displayed side by side with the
differences highlighted.

The main requirements for this are two panes of text, separated
by a narrow drawing_area widget that has a representation of
the full file. There also needs to be a single horizontal and
single vertical scroll bar which will act simultaneously on
both text widgets.

After giving it a brief try, I don't think the scrolled_window
container typesuggested by Olivier will work. The problem is 
that while it is possible to have the two text areas and the 
drawing area inside a scrolled_window I cannot figure out how 
to make the two text widgets appear stay at the same size 
regardless of the size of the parent window.

While thinking about solutions, I have come up with a number
of possibilities:

  - Use two scrolled_window widgets side by side, with the 
    un-needed scrollbars hidden or disabled (not even sure if 
    this is possible). If its not possible to hide the unused
    scrollbars, then they will need to be hooked up so that
    they act in unison (is this possible).

  - Write an Ocaml class that basically emulates a scrolled 
    window with the two text areas and the drawing_area as 
    child widgets. Hopefully this can be done in Ocaml without 
    resorting to C.

  - Put the two text areas, the drawing area and the two 
    scrollbars in a GPack.table and manually connect up the
    signals from the scrollbars to the two text areas as well
    as catch the parent window resize events so the size of
    two text areas can be kept roughly equal.
 
  - Writing a widget in C (hacked from gtk_scrolling_window)
    and then wrapping it in Ocaml. This is probably a poor
    choice because I'd prefer to code in Ocaml and I'd like
    to be able to recompile the program for all three major
    platforms.

There are probably other options that I haven't thought of
yet. So the questions I would like to ask the more experienced
Ocaml/lablgtk2 hackers are:

  0) Is there another possibl better option that I haven't 
     thought of?
  1) Which of the above possibilities is likely to give the 
     results I'm after with the least amount of headaches? 

Thanks in advance.

Cheers,
Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo
+-----------------------------------------------------------+
The idea that Bill Gates has appeared like a knight in shining armour to
lead all customers out of a mire of technological chaos neatly ignores
the fact that it was he who, by peddling second-rate technology, led them
into it in the first place. - Douglas Adams in Guardian, 25-Aug-95