directx的简单例子（打开一个d3d窗口）注意的地方

#include <d3d9.h>
#include <Windows.h>

#pragma comment(lib, "d3d9.lib")
#pragma comment(lib, "d3dx9.lib")

#define WINDOW_CLASS "UGPDX"
#define WINDOW_NAME  "Blank D3D Window"

// Function Prototypes...
bool InitializeD3D(HWND hWnd, bool fullscreen);
void RenderScene();
void Shutdown();

// Direct3D object and device.
LPDIRECT3D9 g_D3D = NULL;
LPDIRECT3DDEVICE9 g_D3DDevice = NULL;

LRESULT WINAPI MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_DESTROY:
PostQuitMessage(0);
return 0;
break;

case WM_KEYUP:
if(wParam == VK_ESCAPE) PostQuitMessage(0);
break;
}

return DefWindowProc(hWnd, msg, wParam, lParam);
}

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE prevhInst, LPSTR cmdLine, int show)
{
// Register the window class
WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
WINDOW_CLASS, NULL };
RegisterClassEx(&wc);

// Create the application's window
HWND hWnd = CreateWindow(WINDOW_CLASS, WINDOW_NAME, WS_OVERLAPPEDWINDOW,
100, 100, 640, 480, GetDesktopWindow(), NULL,
wc.hInstance, NULL);
g_D3D= Direct3DCreate9(D3D_SDK_VERSION);

//Initialize Direct3D
if(InitializeD3D(hWnd, false))
{
// Show the window
ShowWindow(hWnd, SW_SHOWDEFAULT);
UpdateWindow(hWnd);

// Enter the message loop
MSG msg;
ZeroMemory(&msg, sizeof(msg));

while(msg.message != WM_QUIT)
{
if(PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else
RenderScene();
}
}

// Release any and all resources.
Shutdown();

// Unregister our window.
UnregisterClass(WINDOW_CLASS, wc.hInstance);
return 0;
}

bool InitializeD3D(HWND hWnd, bool fullscreen)
{
D3DDISPLAYMODE displayMode;

//Create the D3D object.
g_D3D = Direct3DCreate9(D3D_SDK_VERSION);
if(g_D3D == NULL) return false;

// Get the desktop display mode.
if(FAILED(g_D3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &displayMode)))
return false;

// Set up the structure used to create the D3DDevice
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));

if(fullscreen)
{
d3dpp.Windowed = FALSE;
d3dpp.BackBufferWidth = 640;
d3dpp.BackBufferHeight = 480;
}
else
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = displayMode.Format;

// Create the D3DDevice
if(FAILED(g_D3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, &d3dpp, &g_D3DDevice)))
{
return false;
}

return true;
}

void RenderScene()
{
// Clear the backbuffer.
g_D3DDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0,0,0), 1.0f, 0);

// Begin the scene.  Start rendering.
g_D3DDevice->BeginScene();

// End the scene.  Stop rendering.
g_D3DDevice->EndScene();

// Display the scene.
g_D3DDevice->Present(NULL, NULL, NULL, NULL);
}

void Shutdown()
{
if(g_D3DDevice != NULL) g_D3DDevice->Release();
if(g_D3D != NULL) g_D3D->Release();
}