Re: subclassing textitem

[Damon Chaplin <damon karuna eclipse co uk>]

On Thu, 2011-10-13 at 22:58 +0200, control H wrote:
> Dear Damon, dear list,
> 
> I try to create a new canvas item which is subclassed from
> goocanvastext. This new type implements amongst other things the paint
> and is_item_at methods. What I want to do is that I reuse the methods
> from the parent class. For example in the paint method, I want first
> to use the paint from goocanvastext, and then I use the cr to paint
> some extra things. But how can I access the parents methods? I have
> unsuccessfully tried things like this:
> 
> my_text_paint (GooCanvasItemSimple   *simple,
>                       cairo_t *cr,
>                       const GooCanvasBounds *bounds)
> {
> 
>   GooCanvasTextClass *text_class = GOO_CANVAS_TEXT_GET_CLASS(text);
>   //text_class->goo_canvas_text_paint(simple,cr,bounds); /* does not compile */
>   text_class->paint(simple,cr,bounds); /* does not compile either */
>   ...
>   paint_something_extra(cr);
> }

I think this should work:

  GOO_CANVAS_ITEM_SIMPLE_CLASS (my_text_parent_class)->simple_paint
    (simple, cr, bounds);

The my_text_parent_class variable is set up automatically by the
G_DEFINE_TYPE macros, and depends on the prefix you used there.

Damon