Prelucrarea Input tastatură

Următorul exemplu demonstrează cum se utilizează un semn de omisiune într-un editor de text simplu. Exemplu actualizează în caret poziția ca utilizator tipuri de caractere imprimabile și utilizează chei diferite pentru a vă deplasa prin zona de client.

#define TEXTMATRIX(x, y) *(pTextMatrix + (y * nWindowCharsX) + x) 

// Global variables.

HINSTANCE hinst;      // current instance 
HBITMAP hCaret;       // caret bitmap 
HDC hdc;              // device context  
PAINTSTRUCT ps;       // client area paint info 
static char *pTextMatrix = NULL; // points to text matrix 
static int  nCharX,   // width of char. in logical units 
            nCharY,   // height of char. in logical units 
            nWindowX, // width of client area 
            nWindowY, // height of client area 
            nWindowCharsX, // width of client area 
            nWindowCharsY, // height of client area 
            nCaretPosX,    // x-position of caret 
            nCaretPosY;    // y-position of caret 
static UINT uOldBlink;     // previous blink rate 
int x, y;    // x and y coordinates to use in text matrix 
TEXTMETRIC tm;             // font information 
 
LONG APIENTRY MainWndProc( 
    HWND hwnd,            // window handle 
    UINT message,         // type of message 
    UINT wParam,          // additional information 
    LONG lParam)          // additional information 
{ 
 
    switch (message) 
    { 
        case WM_CREATE: 
        // Select a fixed-width system font, and get its text metrics.
 
            hdc = GetDC(hwnd); 
            SelectObject(hdc, 
                GetStockObject(SYSTEM_FIXED_FONT)); 
            GetTextMetrics(hdc, &tm); 
            ReleaseDC(hwnd, hdc); 
 
        // Save the avg. width and height of characters. 
 
            nCharX = tm.tmAveCharWidth; 
            nCharY = tm.tmHeight; 
 
            return 0; 
 
        case WM_SIZE: 
        // Determine the width of the client area, in pixels 
        // and in number of characters. 
 
            nWindowX = LOWORD(lParam); 
            nWindowCharsX = max(1, nWindowX/nCharX); 
 
            // Determine the height of the client area, in 
            // pixels and in number of characters. 
 
            nWindowY = HIWORD(lParam); 
            nWindowCharsY = max(1, nWindowY/nCharY); 
 
            // Clear the buffer that holds the text input. 
 
            if (pTextMatrix != NULL) 
                free(pTextMatrix); 
 
            // If there is enough memory, allocate space for the 
            // text input buffer. 
 
            pTextMatrix = malloc(nWindowCharsX * nWindowCharsY); 
 
            if (pTextMatrix == NULL) 
                ErrorHandler("Not enough memory."); 
            else 
                for (y = 0; y < nWindowCharsY; y++) 
                    for (x = 0; x < nWindowCharsX; x++) 
                        TEXTMATRIX(x, y) = ' '; 
 
            // Move the caret to the origin. 
 
            SetCaretPos(0, 0); 
 
            return 0; 
 
        case WM_KEYDOWN: 
            switch (wParam) 
            { 
                case VK_HOME:       // Home 
                    nCaretPosX = 0; 
                    break; 
 
                case VK_END:        // End 
                    nCaretPosX = nWindowCharsX - 1; 
                    break; 
 
                case VK_PRIOR:      // Page Up 
                    nCaretPosY = 0; 
                    break; 
 
                case VK_NEXT:       // Page Down 
                    nCaretPosY = nWindowCharsY -1; 
                    break; 
 
                case VK_LEFT:       // Left arrow 
                    nCaretPosX = max(nCaretPosX - 1, 0); 
                    break; 
 
                case VK_RIGHT:      // Right arrow 
                    nCaretPosX = min(nCaretPosX + 1, 
                        nWindowCharsX - 1); 
                    break; 
 
                case VK_UP:         // Up arrow 
                    nCaretPosY = max(nCaretPosY - 1, 0); 
                    break; 
 
                case VK_DOWN:       // Down arrow 
                    nCaretPosY = min(nCaretPosY + 1, 
                        nWindowCharsY - 1); 
                    break; 
 
                case VK_DELETE:     // Delete 
 
                // Move all the characters that followed the 
                // deleted character (on the same line) one 
                // space back (to the left) in the matrix. 
 
                    for (x = nCaretPosX; x < nWindowCharsX; x++) 
                        TEXTMATRIX(x, nCaretPosY) = 
                            TEXTMATRIX(x + 1, nCaretPosY); 
 
                    // Replace the last character on the 
                    // line with a space. 
 
                    TEXTMATRIX(nWindowCharsX - 1, 
                        nCaretPosY) = ' '; 
 
                    // The application will draw outside the 
                    // WM_PAINT message processing, so hide the caret. 
 
                    HideCaret(hwnd); 
 
                    // Redraw the line, adjusted for the 
                    // deleted character. 
 
                    hdc = GetDC(hwnd); 
                    SelectObject(hdc, 
                        GetStockObject(SYSTEM_FIXED_FONT)); 
 
                    TextOut(hdc, nCaretPosX * nCharX, 
                        nCaretPosY * nCharY, 
                        &TEXTMATRIX(nCaretPosX, nCaretPosY), 
                        nWindowCharsX - nCaretPosX); 
 
                    ReleaseDC(hwnd, hdc); 
 
                    // Display the caret. 
 
                    ShowCaret(hwnd); 
 
                    break; 
            } 
 
            // Adjust the caret position based on the 
            // virtual-key processing. 
 
            SetCaretPos(nCaretPosX * nCharX, 
                nCaretPosY * nCharY); 
 
            return 0; 
 
        case WM_CHAR: 
            switch (wParam) 
            { 
                case 0x08:          // Backspace 
                // Move the caret back one space, and then 
                // process this like the DEL key. 
 
                    if (nCaretPosX > 0) 
                    { 
                        nCaretPosX--; 
                        SendMessage(hwnd, WM_KEYDOWN, 
                            VK_DELETE, 1L); 
                    } 
                    break; 
 
                case 0x09:          // Tab 
                // Tab stops exist every four spaces, so add 
                // spaces until the user hits the next tab. 
 
                    do 
                    { 
                        SendMessage(hwnd, WM_CHAR, ' ', 1L); 
                    } while (nCaretPosX % 4 != 0); 
                    break; 
 
                case 0x0D:          // Carriage return 
                // Go to the beginning of the next line. 
                // The bottom line wraps around to the top. 
 
                    nCaretPosX = 0; 
 
                    if (++nCaretPosY == nWindowCharsY) 
                        nCaretPosY = 0; 
                    break; 
 
                case 0x1B:        // Escape 
                case 0x0A:        // Linefeed 
                    MessageBeep((UINT) -1); 
                    break; 
 
                default: 
                // Add the character to the text buffer. 
 
                    TEXTMATRIX(nCaretPosX, nCaretPosY) = 
                        (char) wParam; 
 
                // The application will draw outside the 
                // WM_PAINT message processing, so hide the caret. 
 
                    HideCaret(hwnd); 
 
                // Draw the character on the screen. 
 
                    hdc = GetDC(hwnd); 
                    SelectObject(hdc, 
                        GetStockObject(SYSTEM_FIXED_FONT)); 
 
                    TextOut(hdc, nCaretPosX * nCharX, 
                        nCaretPosY * nCharY, 
                        &TEXTMATRIX(nCaretPosX, nCaretPosY), 1); 
 
                    ReleaseDC(hwnd, hdc); 
 
                    // Display the caret. 
 
                    ShowCaret(hwnd); 
 
                    // Prepare to wrap around if you reached the 
                    // end of the line. 
 
                    if (++nCaretPosX == nWindowCharsX) 
                    { 
                        nCaretPosX = 0; 
                        if (++nCaretPosY == nWindowCharsY) 
                            nCaretPosY = 0; 
                    } 
                    break; 
            } 
 
            // Adjust the caret position based on the 
            // character processing. 
 
            SetCaretPos(nCaretPosX * nCharX, 
                nCaretPosY * nCharY); 
 
            return 0; 
 
        case WM_PAINT: 
        // Draw all the characters in the buffer, line by line. 
 
            hdc = BeginPaint(hwnd, &ps); 
 
            SelectObject(hdc, 
                GetStockObject(SYSTEM_FIXED_FONT)); 
 
            for (y = 0; y < nWindowCharsY; y++) 
                TextOut(hdc, 0, y * nCharY, &TEXTMATRIX(0, y), 
                    nWindowCharsX); 
 
            EndPaint(hwnd, &ps); 
 
        case WM_SETFOCUS: 
        // The window has the input focus. Load the 
        // application-defined caret resource. 
 
            hCaret = LoadBitmap(hinst, MAKEINTRESOURCE(120)); 
 
            // Create the caret. 
 
            CreateCaret(hwnd, hCaret, 0, 0); 
 
            // Adjust the caret position. 
 
            SetCaretPos(nCaretPosX * nCharX, 
                nCaretPosY * nCharY); 
 
            // Display the caret. 
 
            ShowCaret(hwnd); 
 
            break; 
 
        case WM_KILLFOCUS: 
        // The window is losing the input focus, 
        // so destroy the caret. 
 
            DestroyCaret(); 
 
            break; 
 
        default: 
            return DefWindowProc(hwnd, message, wParam, lParam); 
 
    } 
 
    return NULL; 
} 
 

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