DirectX7 SetPalette always failed

DirectX7 SetPalette always failed

I'm learning DirectX, I want to Bind a palette to the PrimarySurface, but
the process always failed. I give my code below:
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 32
#define MAX_COLORS_PALETTE 256
#define DDRAW_INIT_STRUCT(ddstruct) { memset(&ddstruct, 0,
sizeof(ddstruct)); ddstruct.dwSize = sizeof(ddstruct); }
LPDIRECTDRAW7 lpdd = NULL;
LPDIRECTDRAWSURFACE7 lpddPrimarySurface = NULL;
LPDIRECTDRAWPALETTE lpddPalette = NULL;
PALETTEENTRY palette[256];
// Omit the unneccessary content
int GameInit()
{
if (FAILED(DirectDrawCreateEx(NULL, (void**)&lpdd, IID_IDirectDraw7,
NULL)))
return 0;
if (FAILED(lpdd->SetCooperativeLevel(g_GameHwnd, DDSCL_FULLSCREEN |
DDSCL_ALLOWMODEX | DDSCL_EXCLUSIVE | DDSCL_ALLOWREBOOT)))
return 0;
if (FAILED(lpdd->SetDisplayMode(SCREEN_WIDTH, SCREEN_HEIGHT,
SCREEN_BPP, 0, 0)))
return 0;
DDRAW_INIT_STRUCT(ddsd);
ddsd.dwFlags = DDSD_CAPS | DDSD_BACKBUFFERCOUNT;
ddsd.dwBackBufferCount = 1;
ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE | DDSCAPS_COMPLEX |
DDSCAPS_FLIP;
if (FAILED(lpdd->CreateSurface(&ddsd, &lpddPrimarySurface, NULL)))
return 0;
ddsd.ddsCaps.dwCaps = DDSCAPS_BACKBUFFER;
if (FAILED(lpddPrimarySurface->GetAttachedSurface(&ddsd.ddsCaps,
&lpddBackSurface)))
return 0;
memset(palette, 0, MAX_COLORS_PALETTE * sizeof(PALETTEENTRY));
for (int index = 0; index < MAX_COLORS_PALETTE; index++)
{
if (index < 64)
palette[index].peRed = index * 4;
else if (index >= 64 && index < 128)
palette[index].peGreen = (index - 64) * 4;
else if (index >= 128 && index < 192)
palette[index].peBlue = (index - 128) * 4;
else if (index >= 192 && index < 256)
palette[index].peRed = palette[index].peGreen =
palette[index].peBlue = (index - 192) * 4;
palette[index].peFlags = PC_NOCOLLAPSE;
}
if (FAILED(lpdd->CreatePalette(DDPCAPS_8BIT | DDPCAPS_ALLOW256 |
DDPCAPS_INITIALIZE, palette, &lpddPalette, NULL)))
return 0;
**// I always failed to set palette to primary surface here....**
if (FAILED(lpddPrimarySurface->SetPalette(lpddPalette)))
{
MessageBox(NULL, "Failed", NULL, MB_OK);
return 0;
}
DDRAW_INIT_STRUCT(ddsd);
if (FAILED(lpddBackSurface->Lock(NULL, &ddsd, DDLOCK_SURFACEMEMORYPTR
| DDLOCK_WAIT, NULL)))
return 0;
UINT *videoBuffer = (UINT*)ddsd.lpSurface;
for (int y = 0; y < SCREEN_HEIGHT; y++)
{
memset((void*)videoBuffer, y % 256, SCREEN_WIDTH * sizeof(UINT));
videoBuffer += ddsd.lPitch >> 2;
}
if (FAILED(lpddBackSurface->Unlock(NULL)))
return 0;
return 1;
}
I don't know why I always failed to SetPalette to the primary surface. I
set the DisplayMode to 640*480*32, my palette is only 256-color, is this
the reason? But I consult the MSDN, CreatePalette can only create 2Bit,
4Bit, 8Bit palettes. Can a 32-bit display mode be compatible with 8Bit
palette? Where is the problem?
I will be grateful if someone could give me some advice. Thanks.