/* Screen Conversion, VDI Res to 4Colour */


static void ConvertVDIRes_4Colour(void)
{
  Uint32 *edi, *ebp;
  Uint32 *esi;
  Uint32 eax, ebx, ecx;
  int y, x, update;

  /* Get screen addresses, 'edi'-ST screen, 'ebp'-Previous ST screen, 'esi'-PC screen */
  edi = (Uint32 *)pSTScreen;          /* ST format screen 2-plane 4 colors */
  ebp = (Uint32 *)pSTScreenCopy;      /* Previous ST format screen */
  update = ScrUpdateFlag & PALETTEMASK_UPDATEMASK;

  for (y = 0; y < VDIHeight; y++) {

    esi = (Uint32 *)pPCScreenDest;    /* PC format screen, byte per pixel 256 colors */

    x = VDIWidth >> 4;             /* Amount to draw across - in 16-pixels (4 bytes) */

    do          /* x-loop */
    {
      /* Do 16 pixels at one time */
      ebx = *edi;

      if( update || ebx!=*ebp )  /* Update? */
	  {
	    bScreenContentsChanged = TRUE;

        /* Plot pixels */
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
        MED_BUILD_PIXELS_0 ;          /* Generate 'ecx' as pixels [4,5,6,7] */
        PLOT_MED_640_8BIT(3) ;
        MED_BUILD_PIXELS_1 ;          /* Generate 'ecx' as pixels [12,13,14,15] */
        PLOT_MED_640_8BIT(1) ;
        MED_BUILD_PIXELS_2 ;          /* Generate 'ecx' as pixels [0,1,2,3] */
        PLOT_MED_640_8BIT(2) ;
        MED_BUILD_PIXELS_3 ;          /* Generate 'ecx' as pixels [8,9,10,11] */
        PLOT_MED_640_8BIT(0) ;
#else
        MED_BUILD_PIXELS_0 ;          /* Generate 'ecx' as pixels [4,5,6,7] */
        PLOT_MED_640_8BIT(1) ;
        MED_BUILD_PIXELS_1 ;          /* Generate 'ecx' as pixels [12,13,14,15] */
        PLOT_MED_640_8BIT(3) ;
        MED_BUILD_PIXELS_2 ;          /* Generate 'ecx' as pixels [0,1,2,3] */
        PLOT_MED_640_8BIT(0) ;
        MED_BUILD_PIXELS_3 ;          /* Generate 'ecx' as pixels [8,9,10,11] */
        PLOT_MED_640_8BIT(2) ;
#endif
      }

      esi += 4;                       /* Next PC pixels */
      edi += 1;                       /* Next ST pixels */
      ebp += 1;                       /* Next ST copy pixels */
    }
    while( --x );                  /* Loop on X */

    /* Offset to next line */
    pPCScreenDest = (((Uint8 *)pPCScreenDest)+PCScreenBytesPerLine);
  }
}