vc学习历程（5）--经典的时钟代码

来源：互联网发布：大国外交知乎编辑：程序博客网时间：2024/05/21 10:27

这次对这个经典的代码做个分析：

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

#define ID_TIMER 1 ///定时器表识；
#define TWOPI (2 * 3.14159) //2PI

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

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("Clock") ;
     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         = NULL ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH)GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName = NULL ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("Program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

     hwnd = CreateWindow (szAppName, TEXT ("Analog Clock"),
                          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 ;
}

void SetIsotropic (HDC hdc, int cxClient, int cyClient)
{
     SetMapMode (hdc, MM_ISOTROPIC) ;//GetMapMode函数用于从设备环境得到当前的映射模式，SetMapMode函数用于设置设备环境的映射模式。

     SetWindowExtEx (hdc, 1000, 1000, NULL) ;//将一个逻辑单位映射为多少
     SetViewportExtEx (hdc, cxClient / 2, -cyClient / 2, NULL) ;
     SetViewportOrgEx (hdc, cxClient / 2, cyClient / 2, NULL) ;//设置视口原点；
}

void RotatePoint (POINT pt[], int iNum, int iAngle)
{
     int   i ;
     POINT ptTemp ;

     for (i = 0 ; i < iNum ; i++)
     {
          ptTemp.x = (int) (pt[i].x * cos (TWOPI * iAngle / 360) +
               pt[i].y * sin (TWOPI * iAngle / 360)) ;

          ptTemp.y = (int) (pt[i].y * cos (TWOPI * iAngle / 360) -
               pt[i].x * sin (TWOPI * iAngle / 360)) ;

          pt[i] = ptTemp ;
     }
}

void DrawClock (HDC hdc)
{
     int   iAngle ;
     POINT pt[3] ;

     for (iAngle = 0 ; iAngle < 360 ; iAngle += 6)
     {
          pt[0].x =   0 ;
          pt[0].y = 900 ;

          RotatePoint (pt, 1, iAngle) ;

          pt[2].x = pt[2].y = iAngle % 5 ? 33 : 100 ;

          pt[0].x -= pt[2].x /2;
          pt[0].y -= pt[2].y /2;

          pt[1].x = pt[0].x + pt[2].x;
          pt[1].y = pt[0].y + pt[2].y ;

          SelectObject (hdc, CreateSolidBrush(RGB(0,0,255)));//);GetStockObject (BLACK_BRUSH)) ;

          Ellipse (hdc, pt[0].x, pt[0].y, pt[1].x, pt[1].y) ;//画个椭圆，并用画刷进行填充；
     }
}

void DrawHands (HDC hdc, SYSTEMTIME * pst, BOOL fChange)
{
     static POINT pt[3][5] = { 0, -150, 100, 0, 0, 600, -100, 0, 0, -150,
                               0, -200, 50, 0, 0, 800, -50, 0, 0, -200,
                               0,    0,   0, 0, 0,   0,    0, 0, 0, 800 } ;
     int          i, iAngle[3] ;
     POINT        ptTemp[3][5] ;

     iAngle[0] = (pst->wHour * 30) % 360 + pst->wMinute / 2 ;
     iAngle[1] = pst->wMinute * 6+ pst->wSecond /10 ;
     iAngle[2] = pst->wSecond * 6 ;

     memcpy (ptTemp, pt, sizeof (pt)) ;   //是什么意思？由pt所指内存区域复制ptTemp个字节到dest所指内存区域。

     for (i = fChange ? 0 : 2 ; i < 3 ; i++)
     {
          RotatePoint (ptTemp[i], 5, iAngle[i]) ;

          Polyline (hdc, ptTemp[i], 5) ;
     }
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static int        cxClient, cyClient ;
     static SYSTEMTIME stPrevious ;
     BOOL              fChange ;
     HDC               hdc ;
     PAINTSTRUCT       ps ;
     SYSTEMTIME        st ;

     switch (message)
     {
     case WM_CREATE :
          SetTimer (hwnd, ID_TIMER, 1000, NULL) ;
          GetLocalTime (&st) ;
          stPrevious = st ;
          return 0 ;

     case WM_SIZE :                           //这是干吗用的？
         cxClient = LOWORD (lParam) ;        //获取客户区的高度和宽度
          cyClient = HIWORD (lParam) ;
          return 0 ;

     case WM_TIMER :
          GetLocalTime (&st) ;

          fChange = st.wHour   != stPrevious.wHour ||   //判断是否重画表针
                    st.wMinute != stPrevious.wMinute||
     st.wSecond != stPrevious.wSecond;

          hdc = GetDC (hwnd) ;

          SetIsotropic (hdc, cxClient, cyClient) ;//原点移动

          SelectObject (hdc, GetStockObject (WHITE_PEN)) ;//利用白色来覆盖原来的
          DrawHands (hdc, &stPrevious, fChange) ;

          SelectObject (hdc, CreatePen(PS_SOLID,1,RGB(0,0,255)));//GetStockObject (//BLACK_PEN)) ;
          DrawHands (hdc, &st, TRUE) ;

          ReleaseDC (hwnd, hdc) ;

          stPrevious = st ;
          return 0 ;

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

          SetIsotropic (hdc, cxClient, cyClient) ;
          DrawClock    (hdc) ;
          DrawHands    (hdc, &stPrevious, TRUE) ;

          EndPaint (hwnd, &ps) ;
          return 0 ;

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