rndrctmt.c

Multi session 多任务编程的例子

/*------------------------------------------
   RNDRCTMT.C -- Displays Random Rectangles
                 (c) Charles Petzold, 1996
  ------------------------------------------*/

#include <windows.h>
#include <process.h>
#include <stdlib.h>

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

HWND hwnd ;
int  cxClient, cyClient ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
     {
     static char szAppName[] = "RndRctMT" ;
     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, "Random Rectangles",
                          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 Thread (PVOID pvoid)
     {
     HBRUSH hBrush ;
     HDC    hdc ;
     int    xLeft, xRight, yTop, yBottom, iRed, iGreen, iBlue ;

     while (TRUE)
          {
          if (cxClient != 0 || cyClient != 0)
               {
               xLeft   = rand () % cxClient ;
               xRight  = rand () % cxClient ;
               yTop    = rand () % cyClient ;
               yBottom = rand () % cyClient ;
               iRed    = rand () & 255 ;
               iGreen  = rand () & 255 ;
               iBlue   = rand () & 255 ;

               hdc = GetDC (hwnd) ;
               hBrush = CreateSolidBrush (RGB (iRed, iGreen, iBlue)) ;
               SelectObject (hdc, hBrush) ;

               Rectangle (hdc, min (xLeft, xRight), min (yTop, yBottom),
                               max (xLeft, xRight), max (yTop, yBottom)) ;

               ReleaseDC (hwnd, hdc) ;
               DeleteObject (hBrush) ;
               }
          }
     }

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
     {
     switch (iMsg)
          {
          case WM_CREATE :
               _beginthread (Thread, 0, NULL) ;
               return 0 ;

          case WM_SIZE :
               cxClient = LOWORD (lParam) ;
               cyClient = HIWORD (lParam) ;
               return 0 ;

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