DEFINITION Views; (* portable *)

(*Implementation of camera-views with adjustable viewpoints.
  Objects, Gadgets, Display, Display3;

  View = POINTER TO ViewDesc;
  ViewDesc = RECORD ( Gadgets.ViewDesc ) 
  (* Relative viewpoint of viewer object. Vector from top-left camera-view corner
to top-left of contents. *)
   vx, vy: INTEGER;
   time: LONGINT; (* Selection time of viewed gadget. *)

 (* Structure to "store" an area on the display *)
  Block = RECORD
   mask: Display3.Mask; (* Mask bounding the area to be drawn in. *)

  background: INTEGER; (* Background color of camera-views *)
 PROCEDURE CopyView (VAR M: Objects.CopyMsg; from, to: View);
 PROCEDURE ViewHandler (F: Objects.Object; VAR M: Objects.ObjMsg);
 PROCEDURE InitView (F: View);

(* Create a camera-view of F. *)
 PROCEDURE ViewOf (F: Display.Frame): View;

(* Save a description of a rectangular area on the display. RestoreBlock will
issue a DisplayMsg to redraw this part of the display. Note that the mask of
the Block must be used to draw in the area X, Y, W, H as the camera-view might
be clipping parts away. These two procedures provide a portable, safe and memory
efficient way of "storing" parts of the display while drawing temporarily. A
low level way of saving and restoring areas on the display is provided by Effects,
or by module Bitmaps. *)
 PROCEDURE GetBlock (X, Y, W, H: INTEGER; dlink: Objects.Object; VAR b: Block);

(* Restore previously "saved" display area. *)
 PROCEDURE RestoreBlock (b: Block);

END Views.