#!perl

use strict;
use Gtk2 -init;

my $window = Gtk2::Window->new ();
$window->signal_connect (delete_event => sub { Gtk2->main_quit } );

my $vbox = Gtk2::VBox->new;
$window->add ($vbox);

my $check = Gtk2::CheckButton->new ("paint on configure in idle?");
$check->set_active (0);
$vbox->pack_start ($check, 0, 0, 0);

my $but = Gtk2::Button->new ("paint red, now");
$but->signal_connect (clicked => sub {set_to_color ([255*257,0,0])});
$vbox->pack_start ($but, 0, 0, 0);

my $draw = Gtk2::DrawingArea->new ();
$draw->set_size_request (200, 200);
$draw->signal_connect (configure_event => sub {
			 if ($check->get_active ()) {
			   Glib::Idle->add (\&set_to_color, [0, 255*257, 0]);
			 } else {
			   set_to_color ([0, 255*257, 0]);
			 }
		       });
$vbox->pack_start ($draw, 1, 1, 0);

$window->show_all;
Gtk2->main;

sub set_to_color {

  (my ($r, $g, $b)) = @{$_[0]};

  my $cr = Gtk2::Gdk::Cairo::Context->create ($draw->window);
  $cr->set_source_color (Gtk2::Gdk::Color->new ($r, $g, $b));
  $cr->rectangle (0, 0, $draw->allocation->width,
                        $draw->allocation->height);
  $cr->fill ();
  $cr = undef;

  return 0;

}