replace* = Pictures.replace; (* The new graphical object completely replaces whatever was before in the destination area. *)
paint* = Pictures.paint; (* The new graphical object is added to whatever was before in the dertination area. *)
invert* = Pictures.invert; (* The new graphical object inverts whatever was before in the dertination area. The color specifies, which planes are affected (inverted) and which aren't *)
TYPE
Type Frame is declared in this module, but not used, except for defining the clipping areas in
the ...C procedures. It's module Viewer, which actually uses the dsc, next and handle fields.