IMPLEMENTATION MODULE ScreenEditor;

	(********************************************************)
	(*							*)
	(*		Screen data capture			*)
	(*							*)
	(*  Programmer:		P. Moylan			*)
	(*  Last edited:	21 February 1995		*)
	(*  Status:						*)
	(*	Basic features working, but see faults in	*)
	(*	module RowEditor.				*)
	(*							*)
	(********************************************************)

FROM RowEditor IMPORT
    (* type *)	StructureRow,
    (* proc *)	WriteRow, EditRow, NewRow, CombineRows,
		CopyOfRow, AdjustRow, DeleteRow, NewList, NewMenu,
		DumpRow, StartColumn;

FROM SYSTEM IMPORT
    (* proc *)	ADR;

FROM Windows IMPORT
    (* proc *)	OpenSimpleWindow, CloseWindow, SetCursor,
    (* proc *)	WriteLn, WriteString, PressAnyKey;	(* for debugging *)

FROM NumericIO IMPORT				(* for debugging *)
    (* proc *)	WriteAddress, WriteCard;

FROM Menus IMPORT
    (* type *)	MenuOption, MO, OffEdgeOption,
    (* proc *)	SetOptions, OffEdge;

FROM Keyboard IMPORT
    (* proc *)	InKey, PutBack;

FROM FieldEditor IMPORT
    (* var  *)	Byte, Cardinal, Real,
    (* proc *)	DefineFieldType;

FROM Storage1 IMPORT
    (* proc *)	ALLOCATE, DEALLOCATE;

(************************************************************************)

CONST testing = FALSE;

CONST Esc = CHR(27);

TYPE

    Structure = POINTER TO RowHeader;

    (* The fields in a RowHeader record are:				*)
    (*		pointer:	the row structure for this row		*)
    (*		row:		screen position				*)
    (*		up, down:	pointers to adjacent rows		*)

    RowHeader = RECORD
		    pointer: StructureRow;
		    row: CARDINAL;
		    up, down: Structure;
		END (*RECORD*);

(************************************************************************)
(*			    SCREEN OUTPUT				*)
(************************************************************************)

PROCEDURE WriteStructure (w: Window;  S: Structure);

    BEGIN
	WHILE S <> NIL DO
	    WITH S^ DO
		WriteRow (w, pointer, row);
	    END (*WITH*);
	    S := S^.down;
	END (*WHILE*);
    END WriteStructure;

(************************************************************************)
(*		   INTRODUCING A NEW FIELD TO THE SYSTEM		*)
(************************************************************************)

PROCEDURE CreateField (VariableAddress: ADDRESS;  ftype: FieldType;
			screenrow, screencolumn, width: CARDINAL): Structure;

    (* Creates a new structure consisting of a single field.  Before	*)
    (* calling this procedure, the caller should make sure, by calling	*)
    (* FieldEditor.DefineFieldType if necessary, that ftype is a type	*)
    (* already known to module FieldEditor.				*)

    VAR result: Structure;

    BEGIN
	NEW (result);
	WITH result^ DO
	    pointer := NewRow (VariableAddress, ftype, screencolumn, width);
	    row := screenrow;
	    up := NIL;  down := NIL;
	END (*WITH*);
	RETURN result;
    END CreateField;

(************************************************************************)

PROCEDURE CardinalField (VAR (*IN*) variable: CARDINAL;
			screenrow, screencolumn, width: CARDINAL): Structure;

    (* Creates a one-field structure for editing the given CARDINAL	*)
    (* variable.							*)

    BEGIN
	RETURN CreateField (ADR(variable), Cardinal,
					screenrow, screencolumn, width);
    END CardinalField;

(************************************************************************)

PROCEDURE ByteField (VAR (*IN*) variable: BYTE;
			screenrow, screencolumn, width: CARDINAL): Structure;

    (* Creates a one-field structure for editing a BYTE variable.	*)

    BEGIN
	RETURN CreateField (ADR(variable), Byte,
					screenrow, screencolumn, width);
    END ByteField;

(************************************************************************)

PROCEDURE RealField (VAR (*IN*) variable: REAL;
			screenrow, screencolumn, width: CARDINAL): Structure;

    (* Creates a one-field structure for editing a REAL variable.	*)

    BEGIN
	RETURN CreateField (ADR(variable), Real,
					screenrow, screencolumn, width);
    END RealField;

(************************************************************************)

PROCEDURE MenuField (VAR (*IN*) variable: CARDINAL;
		screenrow, screencolumn, lines, width: CARDINAL;
						M: Menu): Structure;

    (* Creates a one-field structure for editing a cardinal variable	*)
    (* via menu selection.  The caller must ensure that M has already	*)
    (* been defined by a call to Menus.					*)

    VAR result: Structure;

    BEGIN
	SetOptions (M, MO{MNoClose,MKeyBack,MNoMouse,MNoTitle,MNoBorder});
	OffEdge (M, return, return, return, return);
	NEW (result);
	WITH result^ DO
	    pointer := NewMenu (variable, M, screencolumn, lines, width);
	    row := screenrow;
	    up := NIL;  down := NIL;
	END (*WITH*);
	RETURN result;
    END MenuField;

(************************************************************************)

PROCEDURE ListField (VAR (*IN*) variable: List;
				screenrow, screencolumn: CARDINAL;
					f: ListFormat): Structure;

    (* Creates a structure for editing a linear list.  The caller must	*)
    (* ensure that f has been defined by a call to module ListEditor.	*)

    VAR result: Structure;

    BEGIN
	NEW (result);
	WITH result^ DO
	    pointer := NewList (variable, f, screencolumn);
	    row := screenrow;
	    up := NIL;  down := NIL;
	END (*WITH*);
	RETURN result;
    END ListField;

(************************************************************************)
(*			    TEST PROCEDURE				*)
(************************************************************************)

PROCEDURE DumpStructure (S: Structure);

    (* For debugging: writes a representation of S to the screen.	*)

    VAR w: Window;

    BEGIN
	OpenSimpleWindow (w, 0, 10, 0, 79);
	WHILE S <> NIL DO
	    WriteLn (w);
	    WriteString (w, "Dumping row ");  WriteCard (w, S^.row);
	    WriteString (w, " @");  WriteAddress (w, S);
	    WriteString (w, ", up = ");  WriteAddress (w, S^.up);
	    WriteString (w, ", down = ");  WriteAddress (w, S^.down);
	    DumpRow (w, S^.pointer);  S := S^.down;
	END (*WHILE*);
	PressAnyKey(w);
	CloseWindow (w);
    END DumpStructure;

(************************************************************************)
(*			  DELETING A STRUCTURE				*)
(************************************************************************)

PROCEDURE DeleteStructure (VAR (*INOUT*) S: Structure);

    (* Deallocates the storage which was used in setting up structure	*)
    (* S.  Note that this has nothing to do with the space used by	*)
    (* variables to which S gives access; we delete only the overhead	*)
    (* space which was originally allocated by this module.		*)

    VAR temp: Structure;

    BEGIN
	WHILE S <> NIL DO
	    DeleteRow (S^.pointer);  temp := S^.down;
	    DISPOSE(S);  S := temp;
	END (*WHILE*);
    END DeleteStructure;

(************************************************************************)
(*		  CONSTRUCTING COMPLEX STRUCTURE TYPES			*)
(************************************************************************)

PROCEDURE Combine (VAR (*INOUT*) A: Structure;  B: Structure);

    (* Strips all of the fields from B and adds them to the existing	*)
    (* fields of A.  Note that B is destroyed in the process.		*)

    VAR previous, current, next, temp: Structure;

    BEGIN
	previous := NIL;  current := A;
	WHILE B <> NIL DO

	    (* Find a place to insert the first element on the B list. *)

	    LOOP
		IF current = NIL THEN EXIT (*LOOP*) END (*IF*);
		next := current^.down;
		IF B^.row <= current^.row THEN EXIT (*LOOP*) END (*IF*);
		previous := current;  current := next;
	    END (*LOOP*);

	    IF (current<>NIL) AND (B^.row = current^.row) THEN

		(* Special case: two rows must be merged. *)

		CombineRows (current^.pointer, B^.pointer);
		temp := B;  B := B^.down;  DISPOSE (temp);

	    ELSE

		(* Take the whole of the B list, insert it below	*)
		(* previous^, then take what remains of the original	*)
		(* destination list and call it the B list.  Swapping	*)
		(* lists like this is a little unconventional, but it	*)
		(* works, and in many cases it speeds up the merge.	*)

		IF previous = NIL THEN
		    A := B;
		ELSE
		    previous^.down := B;
		END (*IF*);
		B^.up := previous;  previous := B;  B := current;
		current := previous^.down;
	    END (*IF*);

	END (*WHILE*);
	(* DumpStructure (A); *)

    END Combine;

(************************************************************************)

PROCEDURE CopyOf (S: Structure): Structure;

    (* Makes a duplicate copy of S.  The variables to be edited are not	*)
    (* duplicated; we simply set up a duplicate set of pointers.	*)

    VAR result, newrow: Structure;

    BEGIN
	result := NIL;
	WHILE S <> NIL DO
	    NEW (newrow);
	    WITH newrow^ DO
		pointer := CopyOfRow (S^.pointer);
		row := S^.row;  up := NIL;  down := NIL;
	    END (*WITH*);
	    Combine (result, newrow);
	    S := S^.down;
	END (*WHILE*);
	RETURN result;
    END CopyOf;

(************************************************************************)

PROCEDURE AdjustAddresses (S: Structure;  addroffset, rowoffset,
						coloffset: CARDINAL);

    (* Adjusts the pointer, row, and column fields of all elements of S	*)
    (* by adding the specified offsets to those fields.			*)

    BEGIN
	WHILE S <> NIL DO
	    AdjustRow (S^.pointer, addroffset, coloffset);
	    INC (S^.row, rowoffset);  S := S^.down;
	END (*WHILE*);
    END AdjustAddresses;

(************************************************************************)

PROCEDURE MakeArray (VAR (*INOUT*) S: Structure;  count: CARDINAL;
		addroffset, rowoffset, coloffset: CARDINAL);

    (* Creates a structure for an array of count elements, where on	*)
    (* entry S is a structure already created for the first array	*)
    (* element.  Parameter addroffset is the difference between		*)
    (* adjacent array elements.  The remaining two parameters give the	*)
    (* offset on the screen between the starting positions of adjacent	*)
    (* array elements.							*)
    (* In this version, I simply replicate item the required number of	*)
    (* times, making appropriate adjustments to the replicated items.	*)
    (* There is probably a more elegant solution which involves the	*)
    (* invention of a new "replicating" type, but that will take more	*)
    (* thought than I have as yet given to the problem.			*)

    VAR current, copy: Structure;  j: CARDINAL;

    BEGIN
	copy := CopyOf(S);
	FOR j := 2 TO count DO

	    current := copy;
	    AdjustAddresses (current, addroffset, rowoffset, coloffset);

	    (* Save a copy for the next time around the loop, then	*)
	    (* incorporate current into the result.			*)

	    copy := CopyOf (current);
	    Combine (S, current);

	END (*FOR*);
	IF testing THEN
	    DumpStructure (S);
	END (*IF*);
	DeleteStructure (copy);
    END MakeArray;

(************************************************************************)
(*			   EDITING A STRUCTURE				*)
(************************************************************************)

PROCEDURE ScreenEdit (w: Window;  S: Structure;  VAR (*OUT*) abort: BOOLEAN);

    (* Displays structure S in window w, and allows the keyboard user	*)
    (* to edit the components of S.  It is assumed that w is already	*)
    (* open and that S has already been fully defined.  Returns		*)
    (* abort=TRUE if user aborted the editing with the Esc key.		*)

    VAR nextchar: CHAR;

    BEGIN
	abort := FALSE;
	IF S = NIL THEN
	    RETURN;
	END (*IF*);
	WriteStructure (w, S);  SetCursor (w, S^.row, StartColumn(S^.pointer));
	LOOP
	    EditRow (w, S^.pointer, S^.row);
	    nextchar := InKey();
	    IF nextchar = CHR(0) THEN
		nextchar := InKey();
		IF (nextchar = "H") AND (S^.up <> NIL) THEN
		    S := S^.up;
		ELSIF (nextchar = "P") AND (S^.down <> NIL) THEN
		    S := S^.down;
		ELSE
		    PutBack (nextchar);  PutBack (CHR(0));
		    EXIT (*LOOP*);
		END (*IF*);
	    ELSIF nextchar = CHR(13) THEN	(* <return> *)
		IF S^.down <> NIL THEN
		    S := S^.down;
		    SetCursor (w, S^.row, StartColumn(S^.pointer));
		ELSE
		    EXIT (*LOOP*);
		END (*IF*);
	    ELSIF nextchar = Esc THEN
		abort := TRUE;
		EXIT (*LOOP*);
	    ELSE
		PutBack (nextchar);
	    END (*IF*);

	END (*LOOP*);

    END ScreenEdit;

(************************************************************************)

END ScreenEditor.