_Ramblings in Real-Time_
by Michael Abrash

Listing One
// try to create a primary buffer and set its format, to configure hardware
#include <windows.h>
#include <dsound.h>

LPDIRECTSOUNDBUFFER SetSoundHWFormat (LPDIRECTSOUND pDS,
   int channels, int bits_per_sample, int samples_per_sec)
{
   DSBUFFERDESC         dsbuf;
   WAVEFORMATEX         format;
   LPDIRECTSOUNDBUFFER  pDSPBuf;

   memset (&format, 0, sizeof(format));
   format.wFormatTag = WAVE_FORMAT_PCM;
   format.nChannels = channels;
   format.wBitsPerSample = bits_per_sample;
   format.nSamplesPerSec = samples_per_sec;
   format.nBlockAlign = format.nChannels*format.wBitsPerSample / 8;
   format.cbSize = 0;
   format.nAvgBytesPerSec = format.nSamplesPerSec*format.nBlockAlign;

   memset (&dsbuf, 0, sizeof(dsbuf));
   dsbuf.dwSize = sizeof(DSBUFFERDESC);
   dsbuf.dwFlags = DSBCAPS_PRIMARYBUFFER;
   dsbuf.dwBufferBytes = 0;
   dsbuf.lpwfxFormat = NULL;

   if (pDS->lpVtbl->CreateSoundBuffer(pDS, &dsbuf, &pDSPBuf, NULL) ==
       DS_OK)
   {
      if (pDSPBuf->lpVtbl->SetFormat (pDSPBuf, &format) == DS_OK)
         return pDSPBuf; // succeeded in configuring hardware
      else
         return NULL;    // didn't succeed in configuring hardware
   }
   else
   {
      return NULL;   // couldn't create a primary buffer
   }
}

Listing Two
// determines whether there's real DirectSound support in the sound
// driver, or just wave-based emulation
#include <windows.h>
#include <dsound.h>

int RealDirectSoundDriver (LPDIRECTSOUND pDS)
{
   DSCAPS   dscaps;

   dscaps.dwSize = sizeof(dscaps);

   if (pDS->lpVtbl->GetCaps (pDS, &dscaps) != DS_OK)
      return 0;   // couldn't get capabilities
   if (dscaps.dwFlags & DSCAPS_EMULDRIVER)
      return 0;   // no real DirectSound driver support, just waves
   else
      return 1;   // real DirectSound driver support
}


Listing Three
// functions to manipulate the desktop video mode
#include <windows.h>

// attempts to set the desktop video mode to the specified
// resolution and bits per pixel
int SetVideoMode (int bpp, int width, int height)
{
   DEVMODE  gdevmode;

   gdevmode.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;
   gdevmode.dmBitsPerPel = bpp;
   gdevmode.dmPelsWidth = width;
   gdevmode.dmPelsHeight = height;

   // CDS_FULLSCREEN keeps icons and windows from being moved to
   // fit within the new dimensions of the desktop
   if (ChangeDisplaySettings (&gdevmode, CDS_FULLSCREEN) !=
          DISP_CHANGE_SUCCESSFUL)
   {
      return 0;
   }
   return 1;
}
// puts back the default desktop video mode
void RestoreDefaultVideoMode (void)
{
   ChangeDisplaySettings (NULL, 0);
}

Listing Four
// functions to start up and shutdown the game configuration for
// the mouse, and to accumulate mouse moves over multiple calls
// during a frame and to calculate the total move for the frame
#include <windows.h>

extern int window_center_x, window_center_y;

// the two 0 values disable the two acceleration thresholds, and the
// 1 value specifies medium mouse speed
static int     originalmouseparms[3], newmouseparms[3] = {0, 0, 1};
static int     mouse_x_accum, mouse_y_accum;
static POINT   current_pos;

int StartGameMouse (void)
{
   if (!SystemParametersInfo (SPI_GETMOUSE, 0, originalmouseparms, 0))
      return 0;
   if (!SystemParametersInfo (SPI_SETMOUSE, 0, newmouseparms, 0))
      return 0;
   ShowCursor (FALSE);
   SetCursorPos (window_center_x, window_center_y);
   return 1;
}
void StopGameMouse (void)
{
   SystemParametersInfo (SPI_SETMOUSE, 0, originalmouseparms, 0);
   ShowCursor (TRUE);
}
void AccumulateGameMouseMove (void)
{
   GetCursorPos (&current_pos);

   mouse_x_accum += current_pos.x - window_center_x;
   mouse_y_accum += current_pos.y - window_center_y;

   // force the mouse to the center, so there's room to move
   SetCursorPos (window_center_x, window_center_y);
}
void GetGameMouseMoveForFrame (int * mouse_x_move, int * mouse_y_move)
{
   GetCursorPos (&current_pos);
   *mouse_x_move = current_pos.x - window_center_x + mouse_x_accum;
   *mouse_y_move = current_pos.y - window_center_y + mouse_y_accum;
   mouse_x_accum = 0;
   mouse_y_accum = 0;

   // force the mouse to the center, so there's room to move
   SetCursorPos (window_center_x, window_center_y);
}