From: brabuhr@...
Date: 2009-12-05T02:22:00+09:00
Subject: Re: Graphics mode again

On Fri, Dec 4, 2009 at 12:11 PM, Teodor Carstea <teodorcarstea@yahoo.com> wrote:
> to unknown (Guest)
>
> yeah! THANKS! By the way, I've made several tests, you don't need x2 and
> y2 at all to draw a single ball.
>
> And... err.. I think there IS something like "repaint", because the
> clock moves its pointers, example:they dissappear at 12:00 mark and
> appear at 12:01. I'll find it. I'll be looking for more documentation
> upon this.
>
> thanks again!

Sure.  Here's a bit better example, I think:

gnome_canvas_ball.rb
require 'gnomecanvas2'

class GnomeCanvasBall
  def initialize(canvas, x, y, radius)
    @canvas, @x, @y, @radius =
     canvas,  x,  y,  radius

    @ellipse = Gnome::CanvasEllipse.new(
      @canvas.root,
      {
        :x1 => @x - @radius, :y1 => @y - @radius,
        :x2 => @x + @radius, :y2 => @y + @radius,
        :fill_color => "white",
        :outline_color => "steelblue",
        :width_pixels => 1
      }
    )
  end

  def show; @ellipse.show; end
  def hide; @ellipse.hide; end

  def x=(val)
    @x = val
    @ellipse.x1 = @x - @radius
    @ellipse.x2 = @x + @radius
  end
  def y=(val)
    @y = val
    @ellipse.y1 = @y - @radius
    @ellipse.y2 = @y + @radius
  end
end

foozle.rb
require 'gnome_canvas_ball'

class Foozle < Gtk::Window
  def initialize
    super

    @canvas = Gnome::Canvas.new(true)

    @foozle = GnomeCanvasBall.new(
      @canvas, 50, 50, 10
    )

    @canvas.show
    add(@canvas)

    signal_connect_after('show') { start }
    signal_connect_after('hide') { stop }
    signal_connect("delete_event") { Gtk::main_quit }
  end

  def start
    @tid= Gtk::timeout_add(1000) {
      @foozle.x = rand(100)
      @foozle.y = rand(100)
      true
    }
  end
  def stop
    Gtk::timeout_remove(@tid) if @tid; @tid = nil
  end
end

Gtk.init(); Foozle.new.show; Gtk.main()