SD2-m2/showcases/showcase_clear.mod

MODULE showcase_clear ;

(*
   m2SDL showcase, ported from SDL-main
   examples/renderer/01-clear/clear.c (public domain).

   Clears the window to a smoothly fading color every frame; the
   sine-wave trick picks the color from the elapsed time.

   SDL3 -> SDL2 adaptations
   - SDL_CreateWindowAndRenderer keeps the SDL2 (w, h, flags,
     win^, ren^) form; SDL_WINDOW_RESIZABLE reused as-is.
   - SDL_SetRenderDrawColorFloat does not exist in SDL2, so the
     0.0..1.0 floats are scaled to Uint8 0..255 here.
   - Callback structure (SDL_AppInit/Iterate/...) is flattened
     into a plain main loop with DrainEvents; auto-quit after 8 s
     so the showcase also terminates unattended.
*)

FROM SYSTEM IMPORT CARDINAL8;
FROM SDL2 IMPORT SDL_Init, SDL_Quit, SDL_Delay,
   SDL_GetTicks, SDL_GetTicks64, SDLInitVideo;
FROM SDLVideo IMPORT WindowHandle, SDL_DestroyWindow, WindowResizable;
FROM SDLRender IMPORT RendererHandle,
   SDL_CreateWindowAndRenderer, SDL_DestroyRenderer,
   SDL_SetRenderDrawColor, SDL_RenderClear, SDL_RenderPresent,
   SDL_RenderSetLogicalSize;
FROM SDLUtils IMPORT DrainEvents;
FROM MathLib0 IMPORT sin, entier;
FROM libc IMPORT printf;

CONST FrameMs = 16; MaxMs = 8000;

VAR
   win: WindowHandle;
   ren: RendererHandle;
   quit: BOOLEAN;
   start: LONGCARD;
   t: REAL;
   r, g, b: INTEGER;

BEGIN
   IF SDL_Init(SDLInitVideo) # 0 THEN
      printf("showcase_clear: SDL_Init failed\n");
      HALT(1)
   END;
   IF SDL_CreateWindowAndRenderer(640, 480, WindowResizable,
                                  win, ren) # 0 THEN
      printf("showcase_clear: CreateWindowAndRenderer failed\n");
      SDL_Quit;
      HALT(1)
   END;
   SDL_RenderSetLogicalSize(ren, 640, 480);

   printf("showcase_clear: fading, close window or wait 8s\n");
   quit := FALSE;
   start := SDL_GetTicks64();
   WHILE NOT quit DO
      DrainEvents(quit);
      (* seconds since start, as REAL (double). *)
      t := VAL(REAL, SDL_GetTicks()) / 1000.0;
      r := entier(127.5 + 127.5 * sin(t));
      g := entier(127.5 + 127.5 * sin(t + 2.0944));
      b := entier(127.5 + 127.5 * sin(t + 4.1888));
      SDL_SetRenderDrawColor(ren, VAL(CARDINAL8, r),
                             VAL(CARDINAL8, g),
                             VAL(CARDINAL8, b),
                             VAL(CARDINAL8, 255));
      SDL_RenderClear(ren);
      SDL_RenderPresent(ren);
      IF SDL_GetTicks64() - start > MaxMs THEN quit := TRUE END;
      SDL_Delay(FrameMs)
   END;

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