MODULE showcase_points ;

(*
   m2SDL3 showcase, ported from SDL upstream
   examples/renderer/04-points/points.c (public domain).

   500 white points drift down-right at 30..60 px/s; points that
   leave the screen respawn at the top or left edge.

   Porting notes
   - SDL_randf() becomes (rand() MOD 10000) / 10000.0 with libc rand.
   - Positions/speeds live in parallel arrays so the whole set goes
     to SDL_RenderPoints in one call, as in the C version.
   - Callback structure flattened into a main loop; auto-quit
     after 8 s so the showcase also terminates unattended.
*)

FROM SYSTEM IMPORT ADDRESS, ADR, CARDINAL8;
FROM SDL3 IMPORT SDL_Init, SDL_Quit, SDL_Delay,
   SDL_GetTicks, SDLInitVideo;
FROM SDL3Video IMPORT WindowHandle, SDL_DestroyWindow, WindowResizable;
FROM SDL3Render IMPORT RendererHandle,
   SDL_CreateWindowAndRenderer, SDL_DestroyRenderer,
   SDL_SetRenderDrawColor, SDL_RenderClear, SDL_RenderPresent,
   SDL_SetRenderLogicalPresentation, LogicalLetterbox,
   SDL_RenderPoints;
FROM SDL3Rect IMPORT SDLFPoint, MakeFPoint;
FROM SDL3Utils IMPORT DrainEvents;
FROM libc IMPORT printf, rand, srand;

CONST FrameMs = 16; MaxMs = 8000;
CONST WinW = 640; WinH = 480; NPoints = 500;
CONST MinSpeed = 30.0; MaxSpeed = 60.0;

VAR
   win: WindowHandle;
   ren: RendererHandle;
   points: ARRAY [0..NPoints-1] OF SDLFPoint;
   speeds: ARRAY [0..NPoints-1] OF REAL;
   quit: BOOLEAN;
   start, last, now: LONGCARD;
   elapsed: REAL;
   i: INTEGER;

(* Random REAL in [0.0, 1.0). *)
PROCEDURE RandF () : REAL;
BEGIN
   RETURN VAL(REAL, rand() MOD 10000) / 10000.0
END RandF;

PROCEDURE RandSpeed () : REAL;
BEGIN
   RETURN MinSpeed + RandF() * (MaxSpeed - MinSpeed)
END RandSpeed;

BEGIN
   IF NOT SDL_Init(SDLInitVideo) THEN
      printf("showcase_points: SDL_Init failed\n");
      HALT(1)
   END;
   IF NOT SDL_CreateWindowAndRenderer("m2SDL3 points",
                                      WinW, WinH,
                                      VAL(LONGCARD, WindowResizable),
                                      win, ren) THEN
      printf("showcase_points: CreateWindowAndRenderer failed\n");
      SDL_Quit;
      HALT(1)
   END;
   SDL_SetRenderLogicalPresentation(ren, WinW, WinH, LogicalLetterbox);

   srand(VAL(INTEGER, SDL_GetTicks()));
   FOR i := 0 TO NPoints - 1 DO
      points[i] := MakeFPoint(VAL(SHORTREAL, RandF() * VAL(REAL, WinW)),
                              VAL(SHORTREAL, RandF() * VAL(REAL, WinH)));
      speeds[i] := RandSpeed()
   END;

   printf("showcase_points: close window or wait 8s\n");
   quit := FALSE;
   start := SDL_GetTicks();
   last := start;
   WHILE NOT quit DO
      DrainEvents(quit);
      now := SDL_GetTicks();
      elapsed := VAL(REAL, now - last) / 1000.0;
      last := now;

      FOR i := 0 TO NPoints - 1 DO
         points[i].x := VAL(SHORTREAL,
                            VAL(REAL, points[i].x)
                            + elapsed * speeds[i]);
         points[i].y := VAL(SHORTREAL,
                            VAL(REAL, points[i].y)
                            + elapsed * speeds[i]);
         IF (VAL(REAL, points[i].x) >= VAL(REAL, WinW))
            OR (VAL(REAL, points[i].y) >= VAL(REAL, WinH)) THEN
            IF rand() MOD 2 = 0 THEN
               points[i].x := VAL(SHORTREAL, RandF() * VAL(REAL, WinW));
               points[i].y := VAL(SHORTREAL, 0.0)
            ELSE
               points[i].x := VAL(SHORTREAL, 0.0);
               points[i].y := VAL(SHORTREAL, RandF() * VAL(REAL, WinH))
            END;
            speeds[i] := RandSpeed()
         END
      END;

      SDL_SetRenderDrawColor(ren, VAL(CARDINAL8, 0), VAL(CARDINAL8, 0),
                             VAL(CARDINAL8, 0), VAL(CARDINAL8, 255));
      SDL_RenderClear(ren);
      SDL_SetRenderDrawColor(ren, VAL(CARDINAL8, 255), VAL(CARDINAL8, 255),
                             VAL(CARDINAL8, 255), VAL(CARDINAL8, 255));
      SDL_RenderPoints(ren, ADR(points), NPoints);
      SDL_RenderPresent(ren);

      IF now - start > MaxMs THEN quit := TRUE END;
      SDL_Delay(FrameMs)
   END;

   SDL_DestroyRenderer(ren);
   SDL_DestroyWindow(win);
   SDL_Quit;
   printf("showcase_points: bye\n")
END showcase_points.