Re: Is there ways to make a atk factory only used for some instances

[Bill Haneman <bill haneman sun com>]

Hi Bolian:

In your example, I would recommend that you create a
GnomeCanvasActiveImage type, so you call
gnome_canvas_active_image_type() when you create your canvas item.  Then
you can register an AtkFactory for this type which will only be used for
GnomeCanvasActiveImage instances, not other GnomeCanvasPixmaps.

I believe that this would also be a nicer way, in general, of adding new
functionality or modifying the behavior of an existing class.  So when
you say that you "made it focusable", etc., I think that these new
properties of your new type of canvas-item deserve their own GType and
class.

Please let me know if I haven't been clear and I will try to explain
further.


best regards,

Bill

------
On Fri, 2003-09-05 at 03:36, Bolian Yin wrote: Hi Bill and Padraig,

Please see the attached picture. The "jump button" (the little yellow
rectangle) is the gnome-canvas-item in question, more accurately, it is
a gnome-canvas-item-pixbuf.  The "jump button" is used to indicate that
there are more events that are not displayed in the day.  Now I have
make it focusable, can jump to the day on receving a Enter Key, then all
the events of the day can be displayed.  This is the action that I want
to export through the atk action interface.

In the current implementation of the jump button in evolution, there are
no new subclass to GnomeCanvasPixbuf, see the code below:

-- code snip begins
-----------------------------------------------------------------------------------

    /* Create the buttons to jump to each days. */
    pixbuf = gdk_pixbuf_new_from_xpm_data ((const char**) jump_xpm);

    for (i = 0; i < E_WEEK_VIEW_MAX_WEEKS * 7; i++) {
        week_view->jump_buttons[i] = gnome_canvas_item_new
            (canvas_group,
             gnome_canvas_pixbuf_get_type (),
             "GnomeCanvasPixbuf::pixbuf", pixbuf,
             NULL);

        g_signal_connect (week_view->jump_buttons[i], "event",
                  G_CALLBACK (e_week_view_on_jump_button_event),
week_view);
    }

/* ... omitted */

e_week_view_on_jump_button_event (GnomeCanvasItem *item,
                  GdkEvent *event,
                  EWeekView *week_view)
{

    /* ... omitted */

    else if (event->type == GDK_KEY_PRESS) {
        /* return, if Tab, Control or Alt is pressed */
        if ((event->key.keyval == GDK_Tab) ||
            (event->key.state & (GDK_CONTROL_MASK | GDK_MOD1_MASK)))
            return FALSE;
        /* with a return key or a simple character, jump to the day */
        if ((event->key.keyval == GDK_Return) ||
            ((event->key.keyval >= 0x20) &&
             (event->key.keyval <= 0xFF))) {
            e_week_view_jump_to_button_item (week_view, item);
            return TRUE;
        }
    }

    /* ... omitted */
}
-- code snip end
-----------------------------------------------------------------------------------


So, the "action" is only supported through the signal handler to
GnomeCanvasPixbuf "event" signal, not in a new subclass. My aim is to
support this action only in the jumpbutton instances, not in any other
instances of GnomeCanvasPixbuf.

Thanks,
-Bolian


Bill Haneman wrote:

    Bolian:
    
    The best way to ensure that an AtkFactory is used only with certain
    instances of a GObject type is to create a new subtype.  In your case,
    this means that GnomeCanvasItem should be subclassed, and an appropriate
    AtkFactory registered for the new type or types.  
    
    GnomeCanvasItem is already an abstract class, so you must already be
    using subclasses.  If your GnomeCanvasItems are instances of existing
    GnomeCanvas subtypes, for instance GnomeCanvasWidget instances, you may
    need to create something like a GnomeCanvasActiveWidget type which is
    used for your 'actionable' canvas items.
    
    regards
    
    Bill
    
    On Thu, 2003-09-04 at 08:06, Bolian Yin wrote:
      
        Hi Padraig,
        
        I met the problem in gnome-canvas-item. Gail has impl for 
        gnome-canvas-item, but programmers can add many functions to a 
        gnome-canvas-item.
        
        For example, a gnome-canvas-item support an action in some context, and 
        want to add a action interface to the atkobject creates for it. In this 
        case, I cannot register a new factory to create the atk object, or all 
        the gnome-canvas-items will create their atk objects using the new factory.
        Is there ways to make a atk factory only used for some instances of 
        gnome-canvas-item, and in other case the default (gail) factory will be 
        used?
        
        Thanks,
        Bolian