正弦函数

#include <windows.h>
#include <math.h>
#include <strsafe.h>

#define NUM 1000
#define TWOPI (2 * 3.14159)

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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) {
    static TCHAR szAppName[] = TEXT("MyWindows");
    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("这个程序需要在 Windows NT 才能执行！"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,
        TEXT("鱼C工作室"),
        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;
    RECT rect;
    POINT apt[NUM];

    int i;
    int iMapMode;
    static int cxClient, cyClient;
    
    switch (message) {
    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        return 0;
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        MoveToEx(hdc, 0, cyClient / 2, NULL);
        LineTo(hdc, cxClient, cyClient / 2);
        MoveToEx(hdc, cxClient/2, 0, NULL);
        LineTo(hdc, cxClient/2 , cyClient);
        
        iMapMode = GetMapMode(hdc);

        SetMapMode(hdc, MM_LOMETRIC);
        SetViewportOrgEx(hdc, 0, cyClient / 2, NULL);

        GetClientRect(hwnd, &rect);
        DPtoLP(hdc, (PPOINT)&rect, 2);

        for (i = 0; i < NUM; i++) {
            apt[i].x = i * (rect.right - rect.left) / NUM;
            apt[i].y = (int)(rect.top * sin(TWOPI * i / NUM));
        }

        MoveToEx(hdc, apt[0].x, apt[0].y, NULL);
        PolylineTo(hdc, apt, NUM);

        SetMapMode(hdc, iMapMode);
        EndPaint(hwnd, &ps);
        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

结果: