Text Editor

#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 wc;

    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH) GetStockObject(WHITE_BRUSH);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = szAppName;

    if(!RegisterClass(&wc))
    {
        MessageBox(NULL, TEXT("Uh oh! Something went wrong! Our developers will fix it ASAP!"), 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;

        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);

        case WM_SIZE:
            if(message == WM_SIZE)
            {
                cxClient = LOWORD(lParam);
                cyClient = HIWORD(lParam);
            }

            cxBuffer = max(1, cxClient / cxChar);
            cyBuffer = max(1, cyClient / cyChar);

            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) = ' ';

            xCaret = 0;
            yCaret = 0;

            if(hwnd == GetFocus())
                SetCaretPos(xCaret * cxChar, yCaret * cyChar);

            InvalidateRect(hwnd, NULL, TRUE);
            return 0;

        case WM_SETFOCUS:
            CreateCaret(hwnd, NULL, cxChar, cyChar);
            SetCaretPos(xCaret * cxChar, yCaret * cyChar);
            ShowCaret(hwnd);
            return 0;

        case WM_KILLFOCUS:
            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);
                    HideCaret(hwnd);
                    hdc = GetDC(hwnd);
                    SelectObject(hdc, CreateFont(0, 0, 0, 0, 0, 0, 0, 0, 0, 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':
                        if(xCaret > 0)
                        {
                            xCaret--;
                            SendMessage(hwnd, WM_KEYDOWN, VK_DELETE, 1);
                        }
                        break;

                    case '\t':
                        do
                        {
                            SendMessage(hwnd, WM_CHAR, '    ', 1);
                        }
                        while(xCaret % 8 != 0);
                        break;

                    case '\r':
                        xCaret = 0;
                        if(++yCaret == cyBuffer)
                            yCaret = 0;
                        break;

                    case '\x1B':
                        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:
                        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);
}