【Windows编程——API】左键连线

//windows.h文件中包含应用程序中所需的数据类型和数据结构的定义
#include <windows.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
#define PI acos(-1)
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);//窗口函数说明
//---------以下初始化窗口类--------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,LPSTR lpszCmdLine,int nCmdShow)
{
    HWND hwnd;
    MSG Msg;
    WNDCLASS wndclass;
    char lpszClassName[] = "窗口";     //窗口类名
    char lpszTitle[] = "My_Windows";    //窗口标题名

    //窗口类的定义
    wndclass.style = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS;                  //窗口类型为默认类型
    wndclass.lpfnWndProc = WndProc;      //窗口处理函数为WndProc
    wndclass.cbClsExtra = 0;             //窗口类无扩展
    wndclass.cbWndExtra = 0;             //窗口实例无扩展
    wndclass.hInstance = hInstance;     //当前实例句柄

    wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);//窗口的最小化图标为默认图标
    wndclass.hCursor = LoadCursor( NULL, IDC_ARROW); //窗口 采用箭头光标
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); //窗口 背景为 白色
    wndclass.lpszMenuName = NULL ; //窗口 中无菜单
    wndclass.lpszClassName = lpszClassName; //窗口类名为“窗口示例”
//-----------以下进行窗口类的注册
    if (!RegisterClass(&wndclass))//如果注册失败则发出警吿声音
    {
        MessageBeep (0);
        return FALSE;
    }

//创建窗口
    hwnd = CreateWindow(
                        lpszClassName, //窗口类名
                        lpszTitle,      //窗口实例的标题名
                        WS_OVERLAPPEDWINDOW, //窗口 的风格
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,  //窗口左上角坐标为默认值
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,  //窗口的髙和宽为默认值
                        NULL,           //此窗口无父窗口
                        NULL,           //此窗口无主菜单
                        hInstance,      //创建此窗口应用程序的当前句柄
                        NULL            //不使用该值
                        );

    ShowWindow( hwnd, nCmdShow);        //显示窗口
    UpdateWindow(hwnd);                 //绘制用户区
    while( GetMessage(&Msg, NULL, 0, 0)) //消息循环
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;                  //程序终止时将信息返回系统
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT message,WPARAM wParam,LPARAM lParam)
{
    HDC hDC, hdc_old;
    HBITMAP hBmp, hBkBmp;
    RECT rect;
    HBRUSH hBrush;
    PAINTSTRUCT Ps;
    TEXTMETRIC tm;
    HFONT hf;
    HPEN hPen;
    SIZE Sz;
    COLORREF color[7] = {RGB(255,0,0), RGB(255,165,0), RGB(255,255,0),
    RGB(0,255,0), RGB(0,255,255), RGB(0,0,255), RGB(139,0,255)};

    char str[150];
    static int x, y, ncount;
    static bool isCircle = false, isRectangle = false;
    static POINT p[1000];//能存的点最大为1000
    switch(message)
    {
    case WM_MOUSEMOVE:
        if (wParam & MK_LBUTTON && ncount < 1000)
        {
            p[ncount].x = MAKEPOINTS(lParam).x;
            p[ncount++].y = MAKEPOINTS(lParam).y;
            hDC = GetDC(hWnd);
            SetPixel(hDC, LOWORD(lParam), HIWORD(lParam), 0L);
            ReleaseDC(hWnd, hDC);
        }
        return 0;
    case WM_LBUTTONDOWN:
        ncount = 0;
        InvalidateRect(hWnd, NULL,1);
        return 0;
    case WM_LBUTTONUP:
        InvalidateRect(hWnd, NULL,1);
        return 0;

    case WM_PAINT:
        GetClientRect(hWnd,&rect);
        hDC = BeginPaint(hWnd, &Ps);

        hPen = CreatePen(PS_SOLID, 1, RGB(0,0,0));
        SelectObject(hDC, hPen);
        for (int i = 0; i < ncount-1; i++)
        {
            MoveToEx(hDC, p[0].x, p[0].y, NULL);
            LineTo(hDC, p[i].x, p[i].y);
        }
        DeleteObject(hPen);

        EndPaint(hWnd, &Ps); //结束缓制

        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    default:
        return  DefWindowProc(hWnd,message,wParam,lParam);
    }
        return 0;
}

原文地址：https://www.cnblogs.com/Vikyanite/p/12641081.html