windows桌面应用程序 直线

您需要一个绘图库来创建直线。在Windows桌面应用程序中，您可以使用GDI（图形设备接口）或Direct2D库来绘制图形。以下是使用GDI库绘制直线的示例代码：

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Line");
    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("Line"),
                        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)
{
    HDC hdc;
    PAINTSTRUCT ps;
    POINT ptStart, ptEnd;

    switch (message)
    {
    case WM_LBUTTONDOWN:
        ptStart.x = LOWORD(lParam);
        ptStart.y = HIWORD(lParam);
        return 0;

    case WM_LBUTTONUP:
        ptEnd.x = LOWORD(lParam);
        ptEnd.y = HIWORD(lParam);
        hdc = GetDC(hwnd);
        MoveToEx(hdc, ptStart.x, ptStart.y, NULL);
        LineTo(hdc, ptEnd.x, ptEnd.y);
        ReleaseDC(hwnd, hdc);
        return 0;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        EndPaint(hwnd, &ps);
        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

这个程序创建了一个窗口，并且在窗口上绘制直线。当用户按下鼠标左键时，程序记录起始点。当用户释放鼠标左键时，程序记录结束点，并且使用GDI库绘制直线。程序使用了Windows消息机制来处理用户事件和绘图操作。