draw_string/[4,5]     draw_string(+Drawable, +X, +Y, +String)
     draw_string(+Drawable, +Gc, +X, +Y, +String)
     
   Draw a text string in Drawable. String is drawn with the origin point of the first character at postion X, Y. String may be either a Prolog atom, or a list of character codes.
Note that this operation affects only pixels in Drawable where the
characters are; the background part of the characters
does not affect Drawable.  If you want the entire area of Drawable
occupied by string to be effected, use draw_image_string.