Re: canvasmm

[Antonio Coralles <noche suapie reflex at>]

Yann Normand wrote:

> Antonio Coralles a écrit :
>
>>I'm really courious about the classes in Gnome::Canvasmm, but only with
>>the reference, i'm somekind of lost, as i dont't have any Gtk+
>>background ... So, what i want to know is, if there are some simple
>>examples, or a tutorial which illustrates the usage of this classes. At
>>the moment i don't even know how to create a gtkmm app which uses a
>>Canvas to display some text ...
>>
>>Thanks, Antonio
>>_______________________________________________
>>gtkmm-list mailing list
>>gtkmm-list gnome org <mailto:gtkmm-list gnome org>
>>http://mail.gnome.org/mailman/listinfo/gtkmm-list
>>
>>  
>>
> Unfortunately, there is no good tutorial the Gnome Canvas with Gtkmm.
> However, you will easily find tutorials on the Gnome Canvas in C. You
> should have no problem porting the examples with Gnomecanvasmm . But be
> careful because the tutorials I read on the web are quite old, and
> therefore were written for the first API version of Gnome Canvas (we are
> now at 2.10). Nevertheless, the differences aren't heavy.
>
> The Canvas object inherits from Gtk::Widget. Thus, you can add it to a
> container just like any widget. It is common to add the Canvas to a
> ScrolledWindow permitting to easily scroll through the Canvas.
>
> I agree that the Gnomecanvasmm reference is poor. You should have a look
> at the Gnome Canvas  API  Reference instead.
>
> -- 
> Yann Normand
> Sogeti-Transiciel
>
Thanks for your tipp ... maybe sombody knows why the follwoing code:

#include <gtkmm/window.h>
#include <gtkmm/main.h>
#include <libgnomecanvasmm/canvas.h>
#include <libgnomecanvasmm/text.h>
#include <libgnomecanvasmm/init.h>
using namespace Gtk;

class CanvasWindow : public Window
{
    public:
    CanvasWindow() : _text(*_canvas.root(), 0, 0, "Hey")
    {
        set_size_request(400, 400);
        add(_canvas);
        show_all_children();
    }
    virtual ~CanvasWindow() {}

    private:
    Gnome::Canvas::Canvas _canvas;
    Gnome::Canvas::Text _text;
   
};

int main(int argc, char **argv)
{
    Gnome::Canvas::init();
    Main kit(argc, argv);
    CanvasWindow win;
    Main::run(win);
}

leads directly to a segfault (i'm using canvasmm-2.6.1). gdb says

Program received signal SIGSEGV, Segmentation fault.
0xb7fb0fa2 in Gnome::Canvas::Item::item_construct () from
/usr/lib/libgnomecanvasmm-2.6.so.1
(gdb) back
#0  0xb7fb0fa2 in Gnome::Canvas::Item::item_construct () from
/usr/lib/libgnomecanvasmm-2.6.so.1
#1  0xb7fbacd3 in Gnome::Canvas::Text::Text () from
/usr/lib/libgnomecanvasmm-2.6.so.1
#2  0x0804beaf in CanvasWindow::CanvasWindow ()
#3  0x0804bd04 in main ()

Thanks,
Antonio