Re: GTK PROGRAM STRUCTURE

["Timothy M. Shead" <tshead k-3d com>]

Dave Reed wrote:

> My standard method (not necessarily the best, but it works nicely for
> me) is to create a class (call it AppGTK) that has all the widgets as
> private data members.  The callbacks are static member functions of
> the class (solves your problem below).  I then have one global
> variable app_gtk.  In each callback, I can then access any of the
> widgets using that global variable and since the callbacks are members
> of the class, they can legally access all the private data.
>
> HTH,
> Dave
>
>
>
> > Date: Fri, 09 Mar 2001 10:10:21 -0500
> > From: CyborgHead netscape net
> >
> > Hi.
> >     A quick question, which is more one of style and programming practice. What is the best way to structure a GTK Program. I have written a program which contains many dialog boxes, all which hold buttons, text boxes etc.. I felt that the best way to program this would be to use classes as I am used to object orientated programming however I found that it could not be effectively done.
> >
> > Having created an instance of a class , b I tried to call
> >
> > gtk_signal_connect_object( GTK_OBJECT( button_setup ), "clicked",
> >         GTK_SIGNAL_FUNC( b.setup ), NULL );
> >
> > This did not work, I then tried to pass the class as a parameter ie.
> >
> > gtk_signal_connect_object( GTK_OBJECT( button_setup ), "clicked",
> >         GTK_SIGNAL_FUNC( global_void_function ), b );
> >
> > and this did not work.
> > Since most of my functions need access to alot of the GtkWidgets I have made nearly all my variables global so they can be accessed by all the functions, but this is crap, and need to improve it cause it is an important project for college. How do you think I should structure the program to have good programming practive and have the variables available to numerous functions.
> >
> > Ciaran

As Dave mentioned, you can connect callbacks to static member functions. 
 As a further refinement, you can pass the "this" pointer to your class 
as the (void*) userdata member in gtk_signal_connect(), then cast it 
back to a class instance pointer in the static method, and use that to 
call the "real", non-static callback method.  Of course, this makes for 
a lot of typing, since each callback has to be written "twice".

Alternatively, you could use a C++ library such as SDPGTK 
(www.k-3d.com), which manages all of this for you by hiding the GTK+ 
callback mechanism behind named "events" - you derive your classes from 
sdpGtkObjectContainer, override the "OnEvent()" method, and dispatch 
events however you like, based on name.  Makes for a very clean, OO way 
of doing things, and sdpGtkObjectContainers can be combined at runtime 
allowing you to encapsulate portions of your UI as "components" at any 
desired level of granularity.  SDPGTK also relies on an XML markup, 
"GTKML" as a very compact, flexible, and end-user-modifiable way to 
specify the layout of your widgets.

Regards,
Timothy M. Shead