MODULE animation;               (* moving turtle example *)
(* demonstrates use of timeout and select() to display a moving turtle in an X11 window *)
IMPORT SYSTEM, gr;

CONST
        Side = 8;       (* nr of pixels of a square side *)

VAR base, stride, screenBufSize :INTEGER;
        currentX :INTEGER;


PROCEDURE drawSquare (x, y, color :INTEGER);
VAR p, i, j :INTEGER;
BEGIN
        p := (y*stride + x*4)*Side;
        ASSERT (p + (Side-1)*stride + (Side-1)*4 <= screenBufSize);
        p := base + p;
        FOR j := 0 TO Side-1 DO
                FOR i := 0 TO Side-1 DO SYSTEM.PUT32 (p, color); INC(p, 4) END;
                p := p + stride - Side*4;
        END;
END drawSquare;


PROCEDURE putLine (x : INTEGER; y: INTEGER;str : ARRAY OF CHAR);
VAR z, x1: INTEGER;
BEGIN
  FOR z := 0 TO LEN(str) - 1 DO
        x1 := (x + z) MOD 100;
    IF str[z] = "b" THEN drawSquare(x1, y, 0600000H); END;  (* brown *)
    IF str[z] = "g" THEN drawSquare(x1, y, 000C000H); END;  (* green *)
  END;
END putLine;


PROCEDURE turtlePicture (x , y : INTEGER);
BEGIN
  putLine(x, y + 0 , "....bb........");
  putLine(x, y + 1 , "....bbb.......");
  putLine(x, y + 2 , "....bbbb......");
  putLine(x, y + 3 , ".bb..bbb......");
  putLine(x, y + 4 , ".bgggbbbgbbgb.");
  putLine(x, y + 5 , ".ggggggggbbbb.");
  putLine(x, y + 6 , "bggggggggbbbb.");
  putLine(x, y + 7 , ".ggggggg......");
  putLine(x, y + 8 , ".bb..bbb......");
  putLine(x, y + 9 , "....bbbb......");
  putLine(x, y + 10, ".....bbb......");
  putLine(x, y + 11, ".....bb.......")
END turtlePicture;


PROCEDURE drawAll;
BEGIN
        gr.screenBegin;
        gr.clear (0C0F0FFH);  (* light blue *)
        turtlePicture (currentX, 15);
        gr.screenEnd;
END drawAll;


PROCEDURE run*;
VAR stop :BOOLEAN;
        ev :gr.EventPars;
        ch :CHAR;
BEGIN
        base := gr.base; stride := gr.stride;
        gr.createWindow (800, 480);
        screenBufSize := gr.winHeight * stride;
        stop := FALSE; currentX := 15;
        drawAll;
        REPEAT
                gr.nextEvent (400, ev);
                IF ev[0] = gr.EventTimeOut THEN
                        drawAll;
                        INC (currentX, 4);
                ELSIF ev[0] = gr.EventKeyPressed THEN
                        ch := CHR(ev[4]);
                        IF (ch = "q") OR (ch = 0AX) OR (ch = " ") THEN stop := TRUE END;
                        IF ev[2] = 9 (* ESC *) THEN stop := TRUE END;
                END;
        UNTIL stop;
        gr.finish;
END run;

BEGIN
        run;
END animation.