[pygtk] gtk.DrawingArea

[Danny Milosavljevic]

Hi,

Am Freitag, den 10.02.2006, 10:44 +0100 schrieb Luigi Paioro:
> [...]

> While I can draw a line on a gtk.gdk.Drawable object, it looks that I 
> cannot delete it. For example I can draw a line using:
> 
> area = gtk.DrawingArea()
> area.window.draw_line(gc, x1, y1, x2, y2)
> 
> but I cannot delete such line... a line isn't identified by an object or 
> an ID and it doesn't exist a proper method to delete it!

What you describe is called a "Canvas". While there are canvas
implementations (DiaCanvas, for example), for this use case, a drawing
area is more than enough.

The way is that the system tells you to repaint a certain area of the
drawing area by emitting a signal ("expose-event"), and in there, you
(clear the area with draw_rectangle and) repaint whatever is "supposed"
to be shown.

If you want to force repaint, call widget.queue_draw().

So what you would do is:

in your button-motion-event:
  set self.x = x, self.y = y
  call widget.queue_draw()

in your expose-event:
  call widget.get_window().draw_rectangle(0, 0, widget.allocation.width,
widget.allocation.height) for clearing the background 
  call widget.get_window().draw_line(self.x, self.y, ...) for the line

cheers,
  Danny