Re: colormaps

[Olexiy Avramchenko <olexiy irtech cn ua>]

Russell Shaw wrote:

> Hi,
>
> In an expose-event callback of a gtk_drawing_area this always paints
> a black region even tho i have it set for white:
>
> gdk_draw_rectangle(widget->window,
>                    background_gc,
>                    TRUE,
>                    event->area.x,
>                    event->area.y,
>                    event->area.width,
>                    event->area.height);
>
>
> I set up the graphics context as:
>
>     background_gc=gdk_gc_new(drawing_area->window);
>     foreground.red=0;
>     foreground.green=0;
>     foreground.blue=0;
>     background.red=0xffff;
>     background.green=0xffff;
>     background.blue=0xffff;
>     gdk_gc_set_foreground(background_gc,&background);
>     gdk_gc_set_background(background_gc,&background);
>     gdk_gc_set_function(background_gc,GDK_COPY);
>
>
> Would i need to do something with creating a new GdkColormap to make 
> it work?

You should allocate colors before gdk_gc_set_*ground calls. You see the 
black color because of zero *pixel* field value in foreground/background 
structures. If you want to avoid color allocation - use 
gdk_gc_set_rgb_*_color functions:
http://developer.gnome.org/doc/API/2.0/gdk/gdk-Graphics-Contexts.html#gdk-gc-set-rgb-fg-color

   Olexiy