Re: Notebooks in Gtk+ v1.2.x

[Carlos Pereira <carlos pehoe civil ist utl pt>]

Jim,
Perhaps I got something wrong, otherwise, pleaaase...

To start with, when you have a problem is a good
ideia to prepare a test program showing the issue,
but this program should be as small as possible,
say 50-80 lines. Your test program had 1060 lines, 
including copyright notices (do you expect them to 
help find the problem?)

Anyway, I compiled and run your test program.
When I change to view1, and then press Zoom in
I get this message:

Gtk-CRITICAL **: file gtkwidget.c: line 1833 (gtk_widget_queue_draw): assertion `widget != NULL' failed.

This usually would mean that your glarea widget is pointing to NULL.
A quick text search in vi showed that you have only two lines
gtk_widget_queue_draw(current->glarea) in the whole file, in
the Zoom In and Zoom Out callbacks. I added a printf and run
again your code: definitely you were passing a NULL argument
for gtk_widget_queue_draw, no wonder your app is crashing!

After that I did another text search in vi, looking for
current->glarea: only the two lines above were found.
(a third one, unrelated, is commented) then I confirmed 
that indeed current is a global variable. The conclusion is, 
current->glarea is never initialized or updated directly. 
Then I found that in fact you use the function:

create_glarea_page ( drawing_area.notebook_page,
                           drawing_area.glarea );

to save the glarea address. The problem here is that, 
in C, arguments are passed by value, so you need to 
pass &drawing_area.glarea, not drawing_area.glarea,
as two printfs one before and other after can
prove, both glareas will point to NULL, you are
just updating drawing_area.glarea inside the function,
outside, drawing_area.glarea still points to NULL!
(automatic refreshs work because the glarea address
is automatically saved when the connect_signal function
is executed).

Then I tried to understand why everytime I ran your
test, I received this message: Page 0 not found!,
apparently you had some problem with your notebook.
I did another text search in vi, this time looking
for "not found" and I came across the code below:
No wonder your test program was printing "Page number 0 not found",
you have this fprintf outside the if, actually
even outside the for! of course it runs always!

typDrawingArea *
find_notebook_page(GSList *list, gint page_number)
{
  int i;
  GSList  *node;
  typDrawingArea *item;

  for (i = 0; (node = g_slist_nth (list, i)); i++)
  {
    item = node->data;

    if (item->page_number == page_number)
    {
      fprintf(stderr,"Page number %d found!\n", item->page_number);
      return (item);
    }
  }
  fprintf(stderr,"Page number %d not found !\n", page_number);
  return (NULL);
}

Carlos