Render DirectX within a window (plus my introduction)

#include <windows.h>
#include <d3d9.h>
#include <d3dx9.h>

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

HWND g_hWnd = NULL; //Window Handle
LPDIRECT3D9 g_pD3D = NULL;
LPDIRECT3DDEVICE9 g_pDevice = NULL; //D3D Device
int xRes = GetSystemMetrics(SM_CXSCREEN); //Screen Resolution Width
int yRes = GetSystemMetrics(SM_CYSCREEN); //Screen Resolution Height

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow);
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
void init(void);
void shutDown(void);
void render(void);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
	WNDCLASSEX winClass; //Window Class Name
	MSG uMsg; //Message Handler

	memset(&uMsg, 0, sizeof(uMsg));

	winClass.lpszClassName = TEXT("MY_WINDOWS_CLASS");
	winClass.cbSize = sizeof(WNDCLASSEX);
	winClass.style = CS_HREDRAW | CS_VREDRAW;
	winClass.lpfnWndProc = WindowProc;
	winClass.hInstance = hInstance;
	winClass.hIcon = NULL;
	winClass.hIconSm = NULL;
	winClass.hCursor = LoadCursor(NULL, IDC_ARROW);
	winClass.hbrBackground = NULL;
	winClass.lpszMenuName = NULL;
	winClass.cbClsExtra = 0;
	winClass.cbWndExtra = 0;

	if(RegisterClassEx(&winClass) == 0)
	{
		return E_FAIL;
	}

	g_hWnd = CreateWindowEx(NULL, TEXT("MY_WINDOWS_CLASS"), TEXT("Direct3D (DX9) - Full Screen"), WS_POPUP | WS_SYSMENU | WS_VISIBLE, 0, 0, xRes, yRes, NULL, NULL, hInstance, NULL);

	if(g_hWnd == NULL)
	{
		return E_FAIL;
	}

	ShowWindow(g_hWnd, nCmdShow);
	UpdateWindow(g_hWnd);

	init();

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

	shutDown();

	UnregisterClass(TEXT("MY_WINDOWS_CLASS"), winClass.hInstance);

	return uMsg.wParam;
}

LRESULT CALLBACK WindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	switch(msg)
	{
	case WM_KEYDOWN:
		{
			switch(wParam)
			{
			case VK_ESCAPE:
				PostQuitMessage(0);
				break;
			case VK_F1:
				//Show info
				break;
			}
		}
		break;

	case WM_CLOSE:
		{
			PostQuitMessage(0);
		}
		break;

	case WM_DESTROY:
		{
			PostQuitMessage(0);
		}
		break;

	default:
		{
			return DefWindowProc(hWnd, msg, wParam, lParam);
		}
		break;
	}

	return 0;
}

void init(void)
{
	g_pD3D = Direct3DCreate9(D3D_SDK_VERSION);

	if(g_pD3D == NULL)
	{
		return;
	}


	int nMode = 0;
	D3DDISPLAYMODE d3ddm;
	bool bDesiredAdapterModeFound = false;

	int nMaxAdapterModes = g_pD3D->GetAdapterModeCount(D3DADAPTER_DEFAULT, D3DFMT_X8R8G8B8);

	for(nMode = 0; nMode < nMaxAdapterModes; ++nMode)
	{
		if(FAILED(g_pD3D->EnumAdapterModes(D3DADAPTER_DEFAULT, D3DFMT_X8R8G8B8, nMode, &d3ddm)))
		{
			return;
		}

		//Does this adapter mode support a mode of xRes x yRes?
		if(d3ddm.Width != xRes || d3ddm.Height != yRes)
		{
			continue;
		}

		//Does this adapter mode support a 32-bit RGB pixel format?
		if(d3ddm.Format != D3DFMT_X8R8G8B8)
		{
			continue;
		}

		//Does this adapter mode support a refresh rate of 85 MHz? - Change this to your maximum refresh rate
		if(d3ddm.RefreshRate != 85)
		{
			continue;
		}

		//We found a match!
		bDesiredAdapterModeFound = true;
		break;
	}

	if(bDesiredAdapterModeFound == false)
	{
		return;
	}


	//Can we get a 32-bit back buffer?
	if(FAILED(g_pD3D->CheckDeviceType(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, D3DFMT_X8R8G8B8, D3DFMT_X8R8G8B8, FALSE)))
	{
		return;
	}

	//Can we get a z-buffer that's at least 16 bits?
	if(FAILED(g_pD3D->CheckDeviceFormat(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, D3DFMT_X8R8G8B8, D3DUSAGE_DEPTHSTENCIL, D3DRTYPE_SURFACE, D3DFMT_D16)))
	{
		return;
	}


	D3DCAPS9 d3dCaps;

	if(FAILED(g_pD3D->GetDeviceCaps(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, &d3dCaps)))
	{
		return;
	}

	DWORD flags = 0;

	if(d3dCaps.VertexProcessingCaps != 0)
	{
		flags = D3DCREATE_HARDWARE_VERTEXPROCESSING;
	} else {
		flags = D3DCREATE_SOFTWARE_VERTEXPROCESSING;
	}


	D3DPRESENT_PARAMETERS d3dpp;
	memset(&d3dpp, 0, sizeof(d3dpp));

	d3dpp.Windowed = false;
	d3dpp.EnableAutoDepthStencil = true;
	d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
	d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
	d3dpp.BackBufferWidth = xRes;
	d3dpp.BackBufferHeight = yRes;
	d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
	d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;

	if(FAILED(g_pD3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, g_hWnd, flags, &d3dpp, &g_pDevice)))
	{
		return;
	}
}

void shutDown(void)
{
	if(g_pDevice != NULL)
	{
		g_pDevice->Release();
	}

	if(g_pD3D != NULL)
	{
		g_pD3D->Release();
	}
}

void render(void)
{
	g_pDevice->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);

	g_pDevice->BeginScene();
	
	//PUT ALL OF YOUR CRAP HERE!
	
	g_pDevice->EndScene();

	g_pDevice->Present(NULL, NULL, NULL, NULL);
}