Re: [gtkmm] Gdk::Colormap and Gdk::Color

[MHL Schulze t-online de (Martin Schulze)]

Am 08.08.2002 06:42 schrieb(en) Michael A. Koziarski:
> Hey guys,  I've been asking on IRC for a while, but as I'm ~12hrs from 
> everyone else I should probably use the list.
>
> The application I'm writing needs to do a fair amount of drawing onto 
> pixmaps etc. so I've been tinkering with Gdk::Drawables lately and I'm 
> wondering whether I've understood the Gdk::Color situation wrt 
> Gdk::Colormaps.  Please point out any errors in the following:
>
> In order to draw a line in a specified color, say red, I need to.
>
> {
> Glib::RefPtr<Gdk::Pixmap> pm = Gdk::Pixmap::create(x,y,d);
> Glib::RefPrt<Gdk::GC> gc = Gdk::GC::create(gc);
> Glib::RefPtr<Gdk::Colormap> cm = gc->get_colorap()
> Gdk::Color red("red");
>
> cm->alloc_color(red);
> pm->draw_line(gc, 0, 0, 100, 100);
> }

I've never used colormaps but from what I see I think that the following
solution should do the same:

{
Glib::RefPtr<Gdk::Pixmap> pm = Gdk::Pixmap::create(x,y,d);
Glib::RefPrt<Gdk::GC> gc = Gdk::GC::create(pm);
Gdk::Color red("red");

gc->set_foreground(red);
pm->draw_line(gc, 0, 0, 100, 100);
}

The foreground color of the GC is used to draw things, the background color
to fill geometric figures.

There is also a convinience function Gdk::GC::set_rgb_fg_color() that hides
some stuff necessary to map an rgb value to a color.

Regards,

  Martin