Re: new object, with variables

[James Scott Jr <skoona verizon net>]

On Thu, 2008-06-12 at 11:12 +0200, Kees Scherpenhuijzen wrote:
> 2008/6/12, James Scott Jr <skoona verizon net>:
> > Kees,
> >
> > I cannot seem figure out what your trying to do.  The code I see in the
> > notes is not something I understand; and I am an experienced gtk
> > developer.
> >
> > Please back away from the code for a minute and try to describe what it
> > is your trying to achieve with this interface or application that
> > spawned this series of notes.  I'm hoping you just started off
> > completely wrong with the wrong assumptions about how to achieve your
> > goal.  In which case I/we can put you back on track.  But for now I
> > cannot keep up.
> >
> > Why do I say this?
> > 1. "i trying to make an object inherited from GTK_ACTION, this all is
> > managed."
> > Response:
> > * If you want to inherit from GTK_ACTION you make a completely new
> > widget.  Look for info on writing widgets from scratch.
> >
> > * Wrapping a function around a g_object_new as you have done in both
> > examples is miss-leading at best.  You cannot make an existing
> > gtk_object do something it was not designed to; i.e. add a struct in its
> > object_new() parms.  You can g_object_set|get_data() on an existing
> > object; register a function for signal from an object so you can modify
> > its external behaviour, on and on...
> >
> > Ok.  Back to "tell me what your trying to do?"
> >
> > James,
> >
> >
> >
> >
> > On Wed, 2008-06-11 at 23:54 +0200, Kees Scherpenhuijzen wrote:
> > > 2008/5/14 Kees Scherpenhuijzen <noik00 gmail com>:
> > > > heyy,
> > > >
> > > > @ the moment i trying to make an object inherited from GTK_ACTION,
> > > > this all is managed.
> > > > Only now i'm trying to initialize the object with an variable,  a
> > > > struct. Ie read the manual about the wrapper that is used, only i
> > > > can't seem
> > > > to find a way in which i can add the struct to g_object_new or otherwise.
> > > >
> > > > to be clear, in this function:
> > > > GtkAction*
> > > > menu_action_new (const gchar *name,
> > > >                 const gchar *label)
> > > > {
> > > >        GtkAction* action;
> > > >        _thunar_return_val_if_fail (name != NULL, NULL);
> > > >        _thunar_return_val_if_fail (label != NULL, NULL);
> > > >
> > > >        action = g_object_new (MENU_TYPE_ACTION,
> > > >                                           "hide-if-empty", FALSE,
> > > >                                           "label", label,
> > > >                                           "name", name,
> > > >                                           NULL);
> > > >        return action;
> > > > }
> > > >
> > > > i want to add the struct so i don't need any get of set functions, is
> > > > this possible?
> > > >
> > > > the thing i want to do is to init :
> > > >  menu_thing    *item;
> > > > in:
> > > > struct _MenuTemplatesAction
> > > > {
> > > >  GtkAction             __parent__;
> > > >  menu_thing    *item;
> > > > };
> > > >
> > > > I hope this enough info to get me close to an answer
> > > >
> > > >
> > > > --
> > > > Kees
> > > >
> > >
> > > Hi,
> > >
> > > I've saw some examples about this problem and tried it with no luck. i
> > > saw that the object was cast and just added.
> > > i've tried:
> > > GtkAction*
> > > menu_action_new (const gchar *name,
> > >                 const gchar *label,
> > >                 Model *model)
> > > {
> > >        GtkAction* action;
> > >        _thunar_return_val_if_fail (name != NULL, NULL);
> > >        _thunar_return_val_if_fail (label != NULL, NULL);
> > >
> > >        action = g_object_new (MENU_TYPE_ACTION,
> > >                                           "hide-if-empty", FALSE,
> > >                                           "label", label,
> > >                                           "name", name,
> > >                                           NULL);
> > >
> > >        MENU_ACTION(action)->items = model;
> > >
> > >        if(G_TYPE_FUNDAMENTAL (action) == G_TYPE_OBJECT)
> > >        {
> > >                g_message(model->menu->name);
> > >                g_message(action->items);
> > >                g_message("test");
> > >        }
> > >        return action;
> > > }
> > > but it seems the second g_message won't print, it gives an segmentation fault.
> > >
> > > extra info: #define MENU_ACTION(obj)
> > > (G_TYPE_CHECK_INSTANCE_CAST ((obj), MENU_TYPE_ACTION,
> > > MenuTemplatesAction))
> > >
> > > What am i missing here?
> > >
> > > Thanks in advance
> > >
> >
> >
> Hey,
> 
> I'm sorry if i'm not clear enough. maybe it's my english :P.
> 
> But to make everything clear:
> I'm  trying to make a widget which can make menuitems out of a struct.
> The struct isn't thought out so i'm not getting to deep in that.
> The template i'm rewriting is found @
> http://svn.xfce.org/svn/xfce/thunar/trunk/thunar/thunar-templates-action.c
> 
> What i'm trying to is when the action is created, I wan't to
> initialize the object with a variable, so when the object is
> shown(thunar_templates_action_menu_shown is used) the variable(struct)
> is initialized.
> 
> I hope this clears the situation a bit.
> 
> And thanks for the help

Kees,

Your English is fine.  It was really the code throwing me off.

I will try to answer some of the memory related questions first.
Assuming you want to add a pointer, to a gtk_action object, of an
allocated memory structure containing instance data; there are two ways
I can thing of getting that done before writing my own widget -- which
makes all things possible.

1. Create the gtk_action first then append a user-data pointer to the
object with g_object_set_data() or g_object_set_data_full().  The full
varient frees the allocated memory when the object is destroyed.

2. Most certainly we will connect a routine to the "activate" signal of
the gtk_action object.  When we connect the signal attach a pointer to
our user-data to the signal using g_object_connect();


typedef struct _your_struct {
gchar   my_string[50];
GtkWidget *my_widget;
gpointer  reserved;
} your_struct;

typedef your_struct *ptr_your_struct;

object = gtk_action_new();
gpointer gptr_your_struct = g_new0(your_struct,1);


Item 1.
g_object_set_data(object,"any-but-same-label", gptr_your_struct)
...
gptr_your_struct = g_object_get_data(object,"any-but-same-label")

Item 2.
g_object_connect(object, "activate",fn_handler, gptr_your_struct, NULL);
...
void fn_handler(GtkAction *action, gpointer user_data)
{
 gptr_your_struct  pData = NULL;

 pData = (gptr_your_struct)user_data;
...
 g_message ("My data is %s", pData->my_string);
...
}

These methods work.  Now if the above is not enough functionality then
you will be creating your own true Widget.  For that all I can say is
"Creating a GTK widget from scratch" is already will documented.
However, look over the tools gtk-demo (its likely already installed),
and devhelp (local api documentation).

Why the segfault? I need to see more code before I can say definitively
- but it seems your approach to menu_action_new() is incorrect, as is
your attempt at creating a widget.  There is more code and structure to
creating a widget.  The one or two routines you posted is not enough for
me (maybe someone else).  I think the whole (widget) thing with the
header will be needed, please post more code so I can see the structure
of the whole widget.

Here is a hint: menu_action_new(0 should create a menu_action object
first! then inside the class init routine create any supporting objects,
like the gtk_action.

James,