Re: Custom widget headache

[David Nečas (Yeti) <yeti physics muni cz>]

On Wed, May 31, 2006 at 05:06:50PM +0200, Daniel Haude wrote:
> I changed over to the g_type system. Actually there wasn't much to change  
> except in the
> cw_area_get_type() function.
>
> Alas, I still get exactly the same output.

Note I only read your code until I find a problem, so this
time it is:

static void cw_area_init(CwArea *area)
{
        static CwArea area_null;
ENTER
        *area = area_null;
        area->policy = GTK_UPDATE_CONTINUOUS;
EXIT
}

What the assignment *area = area_null is supposed to do?

What it does is overwriting class information, reference
count and object data (stuff set with
g_object_set_[q]data()) in area with zeroes, obviously
breaking its GObjectness.  And this was just for GObject
itself, GtkWidget (the direct parent) carefully initialized
its fields too, just to see them wiped out with
*area = area_null.

When you deal with GObjects you have to keep in mind there
is some data in the parent too.   You can define a method for
`assign by value' if your objects are capable of that, but
you cannot just memcopy the content of one object to
another.

> and in the struct definitions (BTW I don't like to use leading underscores  
> for the struct tags because they invade implementation namespace).

Well, prepare for more work with gtk-doc (for instance).
There are tools which understand the standard naming
convetion and do not understand yours.

> The  
> only important thing appears to me that the first member of the struct is  
> the appropriate parent; in this case GtkWidget.

And that's the core of the problem.  GtkWidget is a *part*
of CwArea.

Yeti


--
Anonyms eat their boogers.