win32编程wm_paint处下断的问题，急急急急急急！！！！！！

Question

代码如下：
#include <windows.h>
#include <stdio.h>LRESULT CALLBACK WinSunProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);int WINAPI WinMain(
  HINSTANCE hInstance,      // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,          // command line
  int nCmdShow              // show state
)
{
WNDCLASS wndcls;
wndcls.cbClsExtra=0;
wndcls.cbWndExtra=0;
wndcls.hbrBackground=(HBRUSH)GetStockObject(BLACK_BRUSH);
wndcls.hCursor=LoadCursor(NULL,IDC_CROSS);
wndcls.hIcon=LoadIcon(NULL,IDI_ERROR);
wndcls.hInstance=hInstance;
wndcls.lpfnWndProc=WinSunProc;
wndcls.lpszClassName="Weixin2003";
wndcls.lpszMenuName=NULL;
wndcls.style=CS_HREDRAW | CS_VREDRAW;
RegisterClass(&wndcls); HWND hwnd;
hwnd=CreateWindow("Weixin2003","±±¾©Î¬Ð¿Æѧ¼¼ÊõÅàѵÖÐÐÄ",WS_OVERLAPPEDWINDOW,
0,0,600,400,NULL,NULL,hInstance,NULL); ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd); MSG msg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}LRESULT CALLBACK WinSunProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
)
{
switch(uMsg)
{
case WM_CHAR:
char szChar[20];
sprintf(szChar,"char is %d",wParam);
MessageBox(hwnd,szChar,"weixin",0);
break;
case WM_LBUTTONDOWN:
MessageBox(hwnd,"mouse clicked","weixin",0);
HDC hdc;
hdc=GetDC(hwnd);
TextOut(hdc,0,50,"¼ÆËã»ú±à³ÌÓïÑÔÅàѵ",strlen("¼ÆËã»ú±à³ÌÓïÑÔÅàѵ"));
ReleaseDC(hwnd,hdc);
break;
case WM_PAINT:
HDC hDC;
PAINTSTRUCT ps;
hDC=BeginPaint(hwnd,&ps);
TextOut(hDC,0,0,"άÐÂÅàѵ",strlen("άÐÂÅàѵ"));
EndPaint(hwnd,&ps);
break;
case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"ÊÇ·ñÕæµÄ½áÊø£¿","weixin",MB_YESNO))
{
DestroyWindow(hwnd);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;
}
问题1：在hDC=BeginPaint(hwnd,&ps)处下断，为何窗口无法正常显示？按理说在UpdateWindow(hwnd)后发出一个wm_paint消息，转入case：wm_paint处理过程，窗口重绘，下断后，窗口却显示一下就消失了。往下执行又是如此。窗口为何会显示？又为何会消失？请详加解释此过程。如果说showindow函数是显示窗口，而updatewindows是重绘窗口，那么应该是窗口显示而不重绘而不是消失。这又是为何？
问题2：showwindow与updatewindow到底有何不同？书上说updatewindow发出wm_paint消息，那为何删除updatewindow函数还能发出wm_paint消息，是showwindow发出的吗？为何showwindow也会发出wm_paint消息？没有updatewindow程序照样执行，窗口照样重绘，那么它到底有何作用？

Answer 1

补充：不仅是在hDC=BeginPaint(hwnd,&ps)处下断，在case：wm_paint分支内任何一处下断都会出现所描述的情况。