Controllers.TraceMsg* = RECORD (Controllers.CursorMessage)
         (* (.x, .y) is the obsolete mouse point; it may coincide with actual, i.e (x,y) ≍ (gx,gy), when mouse has just 'moved inside'. Mind that x.y is frame coordinates, while gx,gy is global *)
         modifiers*: SET;   (*** IN *)
         cursor*: INTEGER;   (** OUT; Iff pointer position defined (.gx # MAX(INTEGER)), .cursor is preset to -1; it may be assigned a desired cursor index. Doing so enables (but does not bind) the framework to *not* send another PollCursorMsg *)
         gx*, gy*: INTEGER;   (** IN; global actual mouse coordinates (as opposed to .x, .y, the obsolete mouse coordinates). .gx = MAX(INTEGER) => new mouse point is undefined (i.e. mouse has moved out of host window) *)
      END;
      (** Sent along the point path (i.e. the path in frame forest of all frames that encompass a point) when mouse movement occurs. (x,y) is the obsolete mouse point in frame coords, while (gx,gy) is the actual mouse point in global coords, or MAX(INTEGER), if the latter is undefined *)