Re: I receive a null Gdk::Window with get_window()

[Jonathon Jongsma <jonathon jongsma gmail com>]

On 7/21/05, Eduardo Paz <edupaz2 gmail com> wrote:
> Hi everyone! I'm new in using gtkmm, and I have a lot of questions. I
> know it would be easy but I couldn find the solution looking at the
> API.
> Well, the first one is how i can color the background of a box (for
> example). Here is the code I've written :
> // Constructor of Gtk::Window
> ....
> add(box);
> box.get_window()->set_bakground(..color..);
> ...
> I got a Sig-sev because the Gdk::Window that get_window returns is NULL.
> Is another way to make this or I'm making something wrong??
> _______________________________________________
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> gtkmm-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtkmm-list
> 

Where is 'box' defined?  what is its type? Gtk::Box?

According to the gtkmm tutorial[1], a Gtk::Box does not have a
corresponding window, so calling get_window() won't return anything. 
Read [1] for more information.    Note that even if you surround your
box with an EventBox as mentioned in that chapter, your color will
probably still need to be allocated (a concept that I don't completely
understand yet -- if anybody has a clear description of what
'allocating a color in a colormap' actually means, i'd love to hear
it.), but nevertheless, there's a chapter in the tutorial [2] on
DrawingAreas that provides some examples of setting backgrounds and
using colors.

Hope that helps
jonathon

[1] http://www.gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/ch12.html
[2] http://gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/ch14.html