Symbol insertion function and typer Program

In Windows, there are five basic symbol insertion functions:

Createcaret	Create an insert symbol associated with the window
Setcaretpos	Set the position of the inserted symbol in the window
Showcaret	Show the inserted symbol
Hidecaret	Hide the inserted symbol
Destroycaret	Destroy the inserted symbol

Case wm_paint: HDC = beginpaint (hwnd, & PS); createcaret (hwnd, null,); setcaretpos (); showcaret (hwnd); endpaint (hwnd, & PS ); return 0; Case wm_char: HDC = beginpaint (hwnd, & PS); wsprintf (szbuffer, text ("% C"), tchar (wparam); MessageBox (null, szbuffer, text ("One prompt"), mb_iconerror); hidecaret (hwnd); endpaint (hwnd, & PS); Return 0;

Although the sparrow is small

Below is the typer program, from the fifth edition of Windows program design

#include <windows.h>#define BUFFER(x,y) *(pBuffer + y * cxBuffer + x)LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,                    PSTR szCmdLine, int iCmdShow){     static TCHAR szAppName[] = TEXT ("Typer") ;     HWND         hwnd ;     MSG          msg ;     WNDCLASS     wndclass ;          wndclass.style         = CS_HREDRAW | CS_VREDRAW ;     wndclass.lpfnWndProc   = WndProc ;     wndclass.cbClsExtra    = 0 ;     wndclass.cbWndExtra    = 0 ;     wndclass.hInstance     = hInstance ;     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;     wndclass.lpszMenuName  = NULL ;     wndclass.lpszClassName = szAppName ;          if (!RegisterClass (&wndclass))     {          MessageBox (NULL, TEXT ("This program requires Windows NT!"),                       szAppName, MB_ICONERROR) ;          return 0 ;     }          hwnd = CreateWindow (szAppName, TEXT ("Typing Program"),                          WS_OVERLAPPEDWINDOW,                          CW_USEDEFAULT, CW_USEDEFAULT,                          CW_USEDEFAULT, CW_USEDEFAULT,                          NULL, NULL, hInstance, NULL) ;          ShowWindow (hwnd, iCmdShow) ;     UpdateWindow (hwnd) ;          while (GetMessage (&msg, NULL, 0, 0))     {          TranslateMessage (&msg) ;          DispatchMessage (&msg) ;     }     return msg.wParam ;}LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){     static DWORD   dwCharSet = DEFAULT_CHARSET ;     static int     cxChar, cyChar, cxClient, cyClient, cxBuffer, cyBuffer,                    xCaret, yCaret ;     static TCHAR * pBuffer = NULL ;     HDC            hdc ;     int            x, y, i ;     PAINTSTRUCT    ps ;     TEXTMETRIC     tm ;          switch (message)     {     case WM_INPUTLANGCHANGE:          dwCharSet = wParam ;                                        // fall through     case WM_CREATE:          hdc = GetDC (hwnd) ;          SelectObject (hdc, CreateFont (0, 0, 0, 0, 0, 0, 0, 0,                                   dwCharSet, 0, 0, 0, FIXED_PITCH, NULL)) ;                    GetTextMetrics (hdc, &tm) ;          cxChar = tm.tmAveCharWidth ;          cyChar = tm.tmHeight ;                    DeleteObject (SelectObject (hdc, GetStockObject (SYSTEM_FONT))) ;          ReleaseDC (hwnd, hdc) ;                                        // fall through                     case WM_SIZE:               // obtain window size in pixels          if (message == WM_SIZE)          {               cxClient = LOWORD (lParam) ;               cyClient = HIWORD (lParam) ;          }               // calculate window size in characters                    cxBuffer = max (1, cxClient / cxChar) ;          cyBuffer = max (1, cyClient / cyChar) ;                         // allocate memory for buffer and clear it                    if (pBuffer != NULL)               free (pBuffer) ;          pBuffer = (TCHAR *) malloc (cxBuffer * cyBuffer * sizeof (TCHAR)) ;                    for (y = 0 ; y < cyBuffer ; y++)               for (x = 0 ; x < cxBuffer ; x++)                    BUFFER(x,y) = ' ' ;                                   // set caret to upper left corner          xCaret = 0 ;          yCaret = 0 ;                              if (hwnd == GetFocus ())               SetCaretPos (xCaret * cxChar, yCaret * cyChar) ;          InvalidateRect (hwnd, NULL, TRUE) ;          return 0 ;                         case WM_SETFOCUS:               // create and show the caret                    CreateCaret (hwnd, NULL, cxChar, cyChar) ;          SetCaretPos (xCaret * cxChar, yCaret * cyChar) ;          ShowCaret (hwnd) ;          return 0 ;               case WM_KILLFOCUS:               // hide and destroy the caret          HideCaret (hwnd) ;          DestroyCaret () ;          return 0 ;               case WM_KEYDOWN:          switch (wParam)          {          case VK_HOME:               xCaret = 0 ;               break ;                         case VK_END:               xCaret = cxBuffer - 1 ;               break ;                         case VK_PRIOR:               yCaret = 0 ;               break ;                         case VK_NEXT:               yCaret = cyBuffer - 1 ;               break ;                         case VK_LEFT:               xCaret = max (xCaret - 1, 0) ;               break ;                         case VK_RIGHT:               xCaret = min (xCaret + 1, cxBuffer - 1) ;               break ;                         case VK_UP:               yCaret = max (yCaret - 1, 0) ;               break ;                         case VK_DOWN:               yCaret = min (yCaret + 1, cyBuffer - 1) ;               break ;                         case VK_DELETE:               for (x = xCaret ; x < cxBuffer - 1 ; x++)                    BUFFER (x, yCaret) = BUFFER (x + 1, yCaret) ;                              BUFFER (cxBuffer - 1, yCaret) = ' ' ;                              HideCaret (hwnd) ;               hdc = GetDC (hwnd) ;                         SelectObject (hdc, CreateFont (0, 0, 0, 0, 0, 0, 0, 0,                                   dwCharSet, 0, 0, 0, FIXED_PITCH, NULL)) ;                                   TextOut (hdc, xCaret * cxChar, yCaret * cyChar,                        & BUFFER (xCaret, yCaret),                        cxBuffer - xCaret) ;               DeleteObject (SelectObject (hdc, GetStockObject (SYSTEM_FONT))) ;               ReleaseDC (hwnd, hdc) ;               ShowCaret (hwnd) ;               break ;          }          SetCaretPos (xCaret * cxChar, yCaret * cyChar) ;          return 0 ;               case WM_CHAR:          for (i = 0 ; i < (int) LOWORD (lParam) ; i++)          {               switch (wParam)               {               case '\b':                    // backspace                    if (xCaret > 0)                    {                         xCaret-- ;                         SendMessage (hwnd, WM_KEYDOWN, VK_DELETE, 1) ;                    }                    break ;                                   case '\t':                    // tab                    do                    {                         SendMessage (hwnd, WM_CHAR, ' ', 1) ;                    }                    while (xCaret % 8 != 0) ;                    break ;                                   case '\n':                    // line feed                    if (++yCaret == cyBuffer)                         yCaret = 0 ;                    break ;                                   case '\r':                    // carriage return                    xCaret = 0 ;                                        if (++yCaret == cyBuffer)                         yCaret = 0 ;                    break ;                                   case '\x1B':                  // escape                    for (y = 0 ; y < cyBuffer ; y++)                         for (x = 0 ; x < cxBuffer ; x++)                              BUFFER (x, y) = ' ' ;                                             xCaret = 0 ;                    yCaret = 0 ;                                             InvalidateRect (hwnd, NULL, FALSE) ;                    break ;                                        default:                      // character codes                    BUFFER (xCaret, yCaret) = (TCHAR) wParam ;                                        HideCaret (hwnd) ;                    hdc = GetDC (hwnd) ;                              SelectObject (hdc, CreateFont (0, 0, 0, 0, 0, 0, 0, 0,                                   dwCharSet, 0, 0, 0, FIXED_PITCH, NULL)) ;                    TextOut (hdc, xCaret * cxChar, yCaret * cyChar,                             & BUFFER (xCaret, yCaret), 1) ;                    DeleteObject (                         SelectObject (hdc, GetStockObject (SYSTEM_FONT))) ;                    ReleaseDC (hwnd, hdc) ;                    ShowCaret (hwnd) ;                    if (++xCaret == cxBuffer)                    {                         xCaret = 0 ;                                                  if (++yCaret == cyBuffer)                              yCaret = 0 ;                    }                    break ;               }          }                    SetCaretPos (xCaret * cxChar, yCaret * cyChar) ;          return 0 ;               case WM_PAINT:          hdc = BeginPaint (hwnd, &ps) ;                    SelectObject (hdc, CreateFont (0, 0, 0, 0, 0, 0, 0, 0,                                   dwCharSet, 0, 0, 0, FIXED_PITCH, NULL)) ;                                        for (y = 0 ; y < cyBuffer ; y++)               TextOut (hdc, 0, y * cyChar, & BUFFER(0,y), cxBuffer) ;          DeleteObject (SelectObject (hdc, GetStockObject (SYSTEM_FONT))) ;          EndPaint (hwnd, &ps) ;          return 0 ;               case WM_DESTROY:          PostQuitMessage (0) ;          return 0 ;     }     return DefWindowProc (hwnd, message, wParam, lParam) ;}

The result is as follows: