PeekMessage与GetMessage

BOOL PeekMessage(
  LPMSG lpMsg, 
  HWND hWnd, 
  UINT wMsgFilterMin, 
  UINT wMsgFilterMax, 
  UINT wRemoveMsg 
); 


BOOL GetMessage(
  LPMSG lpMsg, 
  HWND hWnd, 
  UINT wMsgFilterMin, 
  UINT wMsgFilterMax 
); 

参考msdn:

• PeekMessage: This function checks a thread message queue for a message and places the message (if any) in the specified structure.
• GetMessage: This function retrieves a message from the calling thread's message queue and places it in the specified structure. 

解释:

• 函数名:peek---偷看(没消息?我闪!),get---获取(没消息?我等!)
• 参数:PeekMessage比GetMessage多一个wRemoveMsg 参数(用于设置处理完后,是否从队列中移除消息).除了WM_PAINT消息外,GetMessage获取并移除所处理消息,而PeekMessage则可以通过参数设置是否移除所处理消息.
• 返回值:GetMessage---对WM_QUIT消息返回zero,其他消息返回nonzero.PeekMessage---有消息返回nonzero,无消息返回zero.

PeekMessage应用举例(见<Windows程序设计>):

/*----------------------------------------------------------------------
        
  RANDRECT.C --   Displays Random Rectangles
        
                (c) Charles Petzold, 1998
        
-----------------------------------------------------------------------*/
        
#include <windows.h>
        
#include <stdlib.h>// for the rand function
        

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

int cxClient, cyClient ;
        
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
        
                   PSTR szCmdLine, int iCmdShow)
        
{
        
    static TCHAR szAppName[] = TEXT ("RandRect") ;
        
    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 ("This program requires Windows NT!"),
        
                                    szAppName, MB_ICONERROR) ;
        
            return 0 ;
        
    }
        
   
        
    hwnd = CreateWindow (szAppName, TEXT ("Random Rectangles"),
        
                           WS_OVERLAPPEDWINDOW,
        
                           CW_USEDEFAULT, CW_USEDEFAULT,
        
                           CW_USEDEFAULT, CW_USEDEFAULT,
        
                           NULL, NULL, hInstance, NULL) ;
        
   
        
    ShowWindow (hwnd, iCmdShow) ;
        
    UpdateWindow (hwnd) ;
        
   
        
    while (TRUE)
        
    {
        
            if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))//有消息,处理消息,无消息,画随机矩形
        
            {
        
                   if (msg.message == WM_QUIT)//退出
        
                     break ;
        
                   TranslateMessage (&msg) ;
        
                   DispatchMessage (&msg) ;
        
        }
        
            else
        
                   DrawRectangle (hwnd) ;
        
    }
        
    return msg.wParam ;
        
}
        

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
        
{
        
    switch (iMsg)
        
    {
        
    case   WM_SIZE:
        
            cxClient = LOWORD (lParam) ;
        
            cyClient = HIWORD (lParam) ;
        
            return 0 ;
        
        
        
    case   WM_DESTROY:
        
            PostQuitMessage (0) ;
        
            return 0 ;
        
    }
        
    return DefWindowProc (hwnd, iMsg, wParam, lParam) ;
        
}
        
void DrawRectangle (HWND hwnd)
        
{
        
    HBRUSHhBrush ;
        
    HDC           hdc ;
        
    RECT          rect ;
        
   
        
    if (cxClient == 0 || cyClient == 0)
        
            return ;
        
    SetRect (&rect, rand () % cxClient, rand () % cyClient,
        
                          rand () % cxClient, rand () % cyClient) ;
        
    hBrush = CreateSolidBrush (
        
                   RGB (rand () % 256, rand () % 256, rand () % 256)) ;
        
    hdc = GetDC (hwnd) ;
        
    FillRect (hdc, &rect, hBrush) ;
        
    ReleaseDC (hwnd, hdc) ;
        
    DeleteObject (hBrush) ;
        
}