Re: Program Structure

[george young <gry ll mit edu>]

I would suggest that writing object-oriented code in C is hard, especially
to get a clear, clean result. (I know people do it, that's not the point).
This situation calls out for an object oriented language like C++ in which
the widget IS the structure.  There's a perfectly reasonable C++ interface for
gtk called gtk--.  I really think it worth some initial effort to try C++.
You don't have to learn the whole complex powerful flexible blahblahblah
content of the language to use it's basic OO capabilities.

I'm not currently a big gtk-- user ( I've passed beyond the earthly state of
C++ to the splendid world of Python! ), but your discussion seems to cry out
for C++.  Again, C++ is essentially a clean superset of C, so the transition
can be completely gradual.  Just learn how to create a class with constructors
and methods; I think you'll find it makes the problems discussed here melt
away.


On Sun, 8 Apr 2001 02:47:07 -0700 (PDT)
<learfox furry ao net> wrote:

> > I was under the impression that this destroys the widget OOP concept.
> > I was not wanting to make a global variable of any sort, even a structure.
> > I have gone ahead and passed structures or pointers by callback to each
> > part in my program:
>
> Well it orients a part of yer program as one object, say one `window'
> as one object. Because yer trying to make something *useful* from
> something that is OOP, not make an OOP out of something already OOP
> (that's often used in wrappers and portability libraries).
>
>
> > /* I have to put a widget I will modify */
> > menu_selection_ callback (ctree_ptr)
> > {
> >     create_dialog
> > }
> >
> > /* I have to create a structure to pass more  args */
> > file_selection_ok_button_callback(struct(ctree_ptr, selection_dialog_ptr))
> > {
> >     ...
> > }
> >
> > (Note: this is not actual code)
> >
> > This passing of pointers is not too bad, but creating structures just to pass
> >
> > information seems a little tedious.  Can the callbacks employ more than one
> > generic pointer arg?
>
> Oh, I use a global `core structure', ie:
>
> typedef struct {
>
>       inventory_struct **inventory_window;
>       int total_inventory_window;
>
> } core_struct;
>
> This one is allocated in main(), then passed to each widget as the signal
> callback data.  There's no global variables involved as this one is
> declared locally in main().
>
>
> > I guess I could make one big structure as you said and pass it through  the
> > chain.
> > That way I can reduce confusion as to what I am passsing and keep the data
> > from
> > being global.  It will have to be static though.
>
> static can mean a lot of things in C>
>
> But I think I know what yer trying to say, I've been writing GTK+ apps for
> two years now using various styles and I've found this to be the most
> practical.
>
> Sometimes I would dereferance if the signal handler is for a widget
> gauranteed to be within a structure like inventory_window.
>
>
> > Am I making this thing to hard?  Should I just make a bunch of globals?
> > Are globals really that bad?
>
> Yes they are if you go into C++, best advice is to make one local variable
> in main() called the core_struct, and dynamically allocate it.
>
> That struct will hold pointers to all substructures, each substructure
> is like a window with a bunch of GtkWidgets in there.
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