bounce.c

定时器实例

/*---------------------------------------
   BOUNCE.C -- Bouncing Ball Program
               (c) Charles Petzold, 1996
  ---------------------------------------*/

#include <windows.h>

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

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
     {
     static char szAppName[] = "Bounce" ;
     HWND        hwnd ;
     MSG         msg ;
     WNDCLASSEX  wndclass ;

     wndclass.cbSize        = sizeof (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 ;
     wndclass.hIconSm       = LoadIcon (NULL, IDI_APPLICATION) ;

     RegisterClassEx (&wndclass) ;

     hwnd = CreateWindow (szAppName, "Bouncing Ball",
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

     if (!SetTimer (hwnd, 1, 50, NULL))
          {
          MessageBox (hwnd, "Too many clocks or timers!",
                      szAppName, MB_ICONEXCLAMATION | MB_OK) ;
          return FALSE ;
          }

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))
          {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
          }
     return msg.wParam ;
     }

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
     {
     static HBITMAP hBitmap ;
     static int     cxClient, cyClient, xCenter, yCenter, cxTotal, cyTotal,
                    cxRadius, cyRadius, cxMove, cyMove, xPixel, yPixel ;
     HBRUSH         hBrush ;
     HDC            hdc, hdcMem ;
     int            iScale ;

     switch (iMsg)
          {
          case WM_CREATE :
               hdc = GetDC (hwnd) ;
               xPixel = GetDeviceCaps (hdc, ASPECTX) ;
               yPixel = GetDeviceCaps (hdc, ASPECTY) ;
               ReleaseDC (hwnd, hdc) ;
               return 0 ;

          case WM_SIZE :
               xCenter = (cxClient = LOWORD (lParam)) / 2 ;
               yCenter = (cyClient = HIWORD (lParam)) / 2 ;

               iScale = min (cxClient * xPixel, cyClient * yPixel) / 16 ;

               cxRadius = iScale / xPixel ;
               cyRadius = iScale / yPixel ;

               cxMove = max (1, cxRadius / 2) ;
               cyMove = max (1, cyRadius / 2) ;

               cxTotal = 2 * (cxRadius + cxMove) ;
               cyTotal = 2 * (cyRadius + cyMove) ;

               if (hBitmap)
                    DeleteObject (hBitmap) ;

               hdc = GetDC (hwnd) ;
               hdcMem = CreateCompatibleDC (hdc) ;
               hBitmap = CreateCompatibleBitmap (hdc, cxTotal, cyTotal) ;
               ReleaseDC (hwnd, hdc) ;

               SelectObject (hdcMem, hBitmap) ;
               Rectangle (hdcMem, -1, -1, cxTotal + 1, cyTotal + 1) ;

               hBrush = CreateHatchBrush (HS_DIAGCROSS, 0L) ;
               SelectObject (hdcMem, hBrush) ;
               SetBkColor (hdcMem, RGB (255, 0, 255)) ;
               Ellipse (hdcMem, cxMove, cyMove, cxTotal - cxMove,
                                                cyTotal - cyMove) ;
               DeleteDC (hdcMem) ;
               DeleteObject (hBrush) ;
               return 0 ;

          case WM_TIMER :
               if (!hBitmap)
                    break ;

               hdc = GetDC (hwnd) ;
               hdcMem = CreateCompatibleDC (hdc) ;
               SelectObject (hdcMem, hBitmap) ;

               BitBlt (hdc, xCenter - cxTotal / 2,
                            yCenter - cyTotal / 2, cxTotal, cyTotal,
                       hdcMem, 0, 0, SRCCOPY) ;

               ReleaseDC (hwnd, hdc) ;
               DeleteDC (hdcMem) ;

               xCenter += cxMove ;
               yCenter += cyMove ;

               if ((xCenter + cxRadius >= cxClient) ||
                   (xCenter - cxRadius <= 0))
                         cxMove = -cxMove ;

               if ((yCenter + cyRadius >= cyClient) ||
                   (yCenter - cyRadius <= 0))
                         cyMove = -cyMove ;
               return 0 ;

          case WM_DESTROY :
               if (hBitmap)
                    DeleteObject (hBitmap) ;

               KillTimer (hwnd, 1) ;
               PostQuitMessage (0) ;
               return 0 ;
          }
     return DefWindowProc (hwnd, iMsg, wParam, lParam) ;
     }