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Bounds

The bounds method computes the approximate bounding box of a canvas item. In Gnome 1.0, this method is only used in gnome_canvas_item_get_bounds(), a user-visible function to return the bounds of a canvas item. The canvas does not use it at all internally, and most likely you could get away without implementing it, though all the stock items do.

The function should return an item's bounding box in item coordinates; here is the GnomeCanvasRE version:

static void
gnome_canvas_re_bounds (GnomeCanvasItem *item, 
                        double *x1, double *y1, 
                        double *x2, double *y2)
{
  GnomeCanvasRE *re;
  double hwidth;

  re = GNOME_CANVAS_RE (item);

  if (re->width_pixels)
    hwidth = (re->width / item->canvas->pixels_per_unit) / 2.0;
  else
    hwidth = re->width / 2.0;

  *x1 = re->x1 - hwidth;
  *y1 = re->y1 - hwidth;
  *x2 = re->x2 + hwidth;
  *y2 = re->y2 + hwidth;
}