DX11: How do you draw a triangle?

//--------------------------------------------------------------------------------------// File: Tutorial01.cpp//// This application displays a triangle rendered using Direct3D 11.//// Concepts introduced in this tutorial://     Creating a device and swap chain//     Compiling and creating shaders//     Setting up the render target and viewport//     Setting up a simple vertex buffer and its input layout//     Clearing the render target//     Drawing a triangle//     Presenting the rendered frame to the display//// Copyright (c) Microsoft Corporation. All rights reserved.//--------------------------------------------------------------------------------------#include <windows.h>#include <d3d11.h>#include <d3dcompiler.h>//--------------------------------------------------------------------------------------// Structures//--------------------------------------------------------------------------------------struct SimpleVertex{    FLOAT Pos[3]; // (X, Y, Z) coordinates of each vertex};//--------------------------------------------------------------------------------------// Global Variables//--------------------------------------------------------------------------------------HINSTANCE                   g_hInst = NULL;HWND                        g_hWnd = NULL;IDXGISwapChain*             g_pSwapChain = NULL;ID3D11Device*               g_pDevice = NULL;ID3D11DeviceContext*        g_pContext = NULL;ID3D11RenderTargetView*     g_pRenderTargetView = NULL;ID3D11InputLayout*          g_pInputLayout = NULL;ID3D11Buffer*               g_pVertexBuffer = NULL;ID3D11VertexShader*         g_pVertexShader = NULL;ID3D11PixelShader*          g_pPixelShader = NULL;//--------------------------------------------------------------------------------------// Vertex shader and pixel shader source code//--------------------------------------------------------------------------------------CHAR* g_strVS =     "void VS( in float4 posIn : POSITION,\n"    "         out float4 posOut : SV_Position )\n"    "{\n"    "    // Output the vertex position, unchanged\n"    "    posOut = posIn;\n"    "}\n";CHAR* g_strPS =     "void PS( out float4 colorOut : SV_Target )\n"    "{\n"    "    // Make each pixel yellow, with alpha = 1\n"    "    colorOut = float4( 1.0f, 1.0f, 0.0f, 1.0f );\n"    "}\n";//--------------------------------------------------------------------------------------// Forward declarations//--------------------------------------------------------------------------------------HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow );HRESULT InitDeviceAndSwapChain();HRESULT InitDeviceObjects();void InitDeviceContext();LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam );void Render();void CleanupDevice();//--------------------------------------------------------------------------------------// Entry point to the program. Initializes everything and goes into a message processing // loop. Idle time is used to render the scene.//--------------------------------------------------------------------------------------int WINAPI wWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow ){    if( FAILED( InitWindow( hInstance, nCmdShow ) ) )        return 0;    if( FAILED( InitDeviceAndSwapChain() ) )        return 0;    if( FAILED( InitDeviceObjects() ) )    {        CleanupDevice();        return 0;    }    InitDeviceContext();    // Main message loop    MSG msg = { 0 };    while( WM_QUIT != msg.message )    {        if( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )        {            TranslateMessage( &msg );            DispatchMessage( &msg );        }        else        {            Render();        }    }    CleanupDevice();    return (int)msg.wParam;}//--------------------------------------------------------------------------------------// Register class and create window//--------------------------------------------------------------------------------------HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow ){    // Register class    WNDCLASSEX wcex;    wcex.cbSize = sizeof( WNDCLASSEX );    wcex.style = CS_HREDRAW | CS_VREDRAW;    wcex.lpfnWndProc = WndProc;    wcex.cbClsExtra = 0;    wcex.cbWndExtra = 0;    wcex.hInstance = hInstance;    wcex.hIcon = NULL;    wcex.hCursor = LoadCursor( NULL, IDC_ARROW );    wcex.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );    wcex.lpszMenuName = NULL;    wcex.lpszClassName = L"TutorialWindowClass";    wcex.hIconSm = NULL;    if( !RegisterClassEx( &wcex ) )        return E_FAIL;    // Create window    g_hInst = hInstance;    RECT rc = { 0, 0, 640, 480 };    AdjustWindowRect( &rc, WS_OVERLAPPEDWINDOW, FALSE );    g_hWnd = CreateWindow( L"TutorialWindowClass", L"Direct3D 11 Tutorial 1: Triangle",                           WS_OVERLAPPEDWINDOW | WS_VISIBLE,                           CW_USEDEFAULT, CW_USEDEFAULT, rc.right - rc.left, rc.bottom - rc.top,                            NULL, NULL, hInstance, NULL );    if( !g_hWnd )        return E_FAIL;    return S_OK;}//--------------------------------------------------------------------------------------// Create the Direct3D device and DXGI swap chain//--------------------------------------------------------------------------------------HRESULT InitDeviceAndSwapChain(){    HRESULT hr = S_OK;    RECT rc;    GetClientRect( g_hWnd, &rc );    UINT width = rc.right - rc.left;    UINT height = rc.bottom - rc.top;    UINT createDeviceFlags = 0;#ifdef _DEBUG    createDeviceFlags |= D3D11_CREATE_DEVICE_DEBUG;#endif    D3D_DRIVER_TYPE driverTypes[] =    {        D3D_DRIVER_TYPE_HARDWARE,        D3D_DRIVER_TYPE_REFERENCE,    };    UINT numDriverTypes = _countof( driverTypes );    D3D_FEATURE_LEVEL featureLevels[] =     {        D3D_FEATURE_LEVEL_11_0,        D3D_FEATURE_LEVEL_10_1,        D3D_FEATURE_LEVEL_10_0,    };    UINT numFeatureLevels = _countof(featureLevels);    D3D_FEATURE_LEVEL featureLevelOut;    DXGI_SWAP_CHAIN_DESC sd;    ZeroMemory( &sd, sizeof( sd ) );    sd.BufferCount = 1;    sd.BufferDesc.Width = width;    sd.BufferDesc.Height = height;    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;    sd.BufferDesc.RefreshRate.Numerator = 60;    sd.BufferDesc.RefreshRate.Denominator = 1;    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;    sd.OutputWindow = g_hWnd;    sd.SampleDesc.Count = 1;    sd.SampleDesc.Quality = 0;    sd.Windowed = TRUE;    D3D_DRIVER_TYPE driverType;    for( UINT driverTypeIndex = 0; driverTypeIndex < numDriverTypes; driverTypeIndex++ )    {        driverType = driverTypes[driverTypeIndex];        hr = D3D11CreateDeviceAndSwapChain( NULL, driverType, NULL, createDeviceFlags,                                            featureLevels, numFeatureLevels, D3D11_SDK_VERSION,                                             &sd, &g_pSwapChain, &g_pDevice, &featureLevelOut,                                             &g_pContext );        if( SUCCEEDED( hr ) )            break;    }    return hr;}//--------------------------------------------------------------------------------------// Use the Direct3D device to create additional objects needed for rendering//--------------------------------------------------------------------------------------HRESULT InitDeviceObjects(){    HRESULT hr = S_OK;        // Create the render target view    ID3D11Texture2D* pRenderTargetTexture;    hr = g_pSwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), (LPVOID*)&pRenderTargetTexture );    if( FAILED( hr ) )        return hr;    hr = g_pDevice->CreateRenderTargetView( pRenderTargetTexture, NULL, &g_pRenderTargetView );    pRenderTargetTexture->Release();    if( FAILED( hr ) )        return hr;    // Compile and create the vertex shader    DWORD dwShaderFlags = D3D10_SHADER_ENABLE_STRICTNESS;#ifdef _DEBUG    dwShaderFlags |= D3D10_SHADER_DEBUG;#endif    ID3D10Blob* pBlobVS = NULL;    ID3D10Blob* pBlobError = NULL;    hr = D3DCompile( g_strVS, lstrlenA( g_strVS ) + 1, "VS", NULL, NULL, "VS",                      "vs_4_0", dwShaderFlags, 0, &pBlobVS, &pBlobError );    if( FAILED( hr ) )    {        if( pBlobError != NULL )        {            OutputDebugStringA( (CHAR*)pBlobError->GetBufferPointer() );            pBlobError->Release();        }        return hr;    }    hr = g_pDevice->CreateVertexShader( pBlobVS->GetBufferPointer(), pBlobVS->GetBufferSize(),                                         NULL, &g_pVertexShader );    if( FAILED( hr ) )        return hr;    // Compile and create the pixel shader    ID3D10Blob* pBlobPS = NULL;    hr = D3DCompile( g_strPS, lstrlenA( g_strPS ) + 1, "PS", NULL, NULL, "PS",                      "ps_4_0", dwShaderFlags, 0, &pBlobPS, &pBlobError );    if( FAILED( hr ) )    {        if( pBlobError != NULL )        {            OutputDebugStringA( (CHAR*)pBlobError->GetBufferPointer() );            pBlobError->Release();        }        return hr;    }    hr = g_pDevice->CreatePixelShader( pBlobPS->GetBufferPointer(), pBlobPS->GetBufferSize(),                                        NULL, &g_pPixelShader );    if( FAILED( hr ) )        return hr;    pBlobPS->Release();    // Create the input layout    D3D11_INPUT_ELEMENT_DESC elements[] =    {        { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, D3D11_APPEND_ALIGNED_ELEMENT, D3D11_INPUT_PER_VERTEX_DATA, 0 },    };    UINT numElements = _countof( elements );    hr = g_pDevice->CreateInputLayout( elements, numElements, pBlobVS->GetBufferPointer(),                                       pBlobVS->GetBufferSize(), &g_pInputLayout );    if( FAILED( hr ) )        return hr;    pBlobVS->Release();    // Create the vertex buffer    SimpleVertex vertices[] =    {        0.0f, 0.5f, 0.5f,        0.5f, -0.5f, 0.5f,        -0.5f, -0.5f, 0.5f,    };    D3D11_BUFFER_DESC bd;    bd.Usage = D3D11_USAGE_DEFAULT;    bd.ByteWidth = sizeof( vertices );    bd.BindFlags = D3D11_BIND_VERTEX_BUFFER;    bd.CPUAccessFlags = 0;    bd.MiscFlags = 0;    bd.StructureByteStride = 0;    D3D11_SUBRESOURCE_DATA initData;    initData.pSysMem = vertices;    hr = g_pDevice->CreateBuffer( &bd, &initData, &g_pVertexBuffer );    if( FAILED( hr ) )        return hr;    return hr;}//--------------------------------------------------------------------------------------// Set up the device context//--------------------------------------------------------------------------------------void InitDeviceContext(){    g_pContext->IASetInputLayout( g_pInputLayout );    UINT stride = sizeof( SimpleVertex );    UINT offset = 0;    g_pContext->IASetVertexBuffers( 0, 1, &g_pVertexBuffer, &stride, &offset );    g_pContext->IASetPrimitiveTopology( D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST );    g_pContext->VSSetShader( g_pVertexShader, NULL, 0 );    g_pContext->PSSetShader( g_pPixelShader, NULL, 0 );    RECT rc;    GetClientRect( g_hWnd, &rc );    D3D11_VIEWPORT vp;    vp.Width = (FLOAT)(rc.right - rc.left);    vp.Height = (FLOAT)(rc.bottom - rc.top);    vp.MinDepth = 0.0f;    vp.MaxDepth = 1.0f;    vp.TopLeftX = 0;    vp.TopLeftY = 0;    g_pContext->RSSetViewports( 1, &vp );    g_pContext->OMSetRenderTargets( 1, &g_pRenderTargetView, NULL );}//--------------------------------------------------------------------------------------// Called every time the application receives a message//--------------------------------------------------------------------------------------LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam ){    PAINTSTRUCT ps;    HDC hdc;    switch( message )    {        case WM_PAINT:            hdc = BeginPaint( hWnd, &ps );            EndPaint( hWnd, &ps );            break;        case WM_CHAR:            if( wParam == VK_ESCAPE )                DestroyWindow( hWnd );            break;        case WM_DESTROY:            PostQuitMessage( 0 );            break;        default:            return DefWindowProc( hWnd, message, wParam, lParam );    }    return 0;}//--------------------------------------------------------------------------------------// Render a frame//--------------------------------------------------------------------------------------void Render(){    // Clear the render target to dark blue    float ClearColor[4] = { 0.0f, 0.125f, 0.3f, 1.0f }; // red, green, blue, alpha    g_pContext->ClearRenderTargetView( g_pRenderTargetView, ClearColor );    // Render a triangle    g_pContext->Draw( 3, 0 );    // Show the rendered frame on the screen    g_pSwapChain->Present( 0, 0 );}//--------------------------------------------------------------------------------------// Destroy the objects we've created//--------------------------------------------------------------------------------------void CleanupDevice(){    if( g_pVertexShader != NULL )        g_pVertexShader->Release();    if( g_pPixelShader != NULL )        g_pPixelShader->Release();    if( g_pVertexBuffer != NULL )        g_pVertexBuffer->Release();    if( g_pInputLayout != NULL )        g_pInputLayout->Release();    if( g_pRenderTargetView != NULL )        g_pRenderTargetView->Release();    if( g_pContext != NULL )        g_pContext->Release();    if( g_pSwapChain != NULL )        g_pSwapChain->Release();    if( g_pDevice != NULL )        g_pDevice->Release();}