一个关于MDIClient窗口的问题

[ronbado]

在主窗口内有一个窗口MDIClient，现在我要在该窗口下生成一个窗口，就叫MyMDIClient，父类是CWnd，目的是要在这个窗口内绘制一个图片作为我的应用程序的底纹。但是MyMDIClient的OnPaint却触发不了。

下边是我的实现
app::InitInstance()
{
//其他省略
pMainFrame->ShowWindow(m_nCmdShow);
pMainFrame->UpdateWindow();
}

CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
//其他省略
if (!MyMDIClient->SubclassWindow (m_hWndMDIClient))
return -1;
}

CMyMDIClient::OnPaint()
{
//可以不看，因为onpaint没有触发
CPaintDC dcPaint(this);

BITMAP bmpMainBack;
CBitmap * pbpMainBack,bpMem,*pbpMemOld;

//取得窗口客户区与刷新区大小
RECT rcClient,rcClip;
GetClientRect(&rcClient);
dcPaint.GetClipBox (&rcClip);

//创建内存设备文本
CDC dcMem,dcBmp;
BOOL bCreateDCSuccess=FALSE;
if ((dcPaint.GetDeviceCaps(RASTERCAPS) & RC_BITBLT)!= 0)
{
if( dcMem.CreateCompatibleDC(&dcPaint) && dcBmp.CreateCompatibleDC(&dcMem))
{
if (bpMem.CreateCompatibleBitmap (&dcPaint,rcClip.right -rcClip.left ,rcClip.bottom -rcClip.top ))
{
dcMem.OffsetViewportOrg (-rcClip.left ,-rcClip.top );
pbpMemOld=dcMem.SelectObject (&bpMem);
bCreateDCSuccess=TRUE;
}
}
}

//创建内存设备文本失败，则退出
if (!bCreateDCSuccess)
{
if (dcMem.m_hDC )
dcMem.DeleteDC ();
if (dcBmp.m_hDC )
dcBmp.DeleteDC ();
return;
}

pbpMainBack=new CBitmap;
pbpMainBack->LoadBitmap (IDB_MAINBACK);
pbpMainBack->GetBitmap (&bmpMainBack);

/* //固定需要刷新的区域
m_rcClip.left =bmpMainMenu.bmWidth ;
m_rcClip.top =0;
m_rcClip.right =m_rcClip.left +bmpSubMenu.bmWidth+10 ;
m_rcClip.bottom =bmpSubMenu.bmHeight ;*/

CBitmap* pbpBmpOld=NULL;

//记录主背景起始行列坐标
int iMainBackX=0;
int iMainBackY=0;

//绘制主背景
if (pbpBmpOld)
dcBmp.SelectObject (pbpMainBack);
else
pbpBmpOld=dcBmp.SelectObject(pbpMainBack);

if (iMainBackX+bmpMainBack.bmWidth <rcClient.right -rcClient.left )
dcMem.StretchBlt (iMainBackX-5,iMainBackY,rcClient.right -iMainBackX+15 ,rcClient.bottom -rcClient.top-iMainBackY ,&dcBmp,0,0,bmpMainBack.bmWidth ,bmpMainBack.bmHeight,SRCCOPY);
else
dcMem.BitBlt (iMainBackX-5,iMainBackY,bmpMainBack.bmWidth,bmpMainBack.bmHeight ,&dcBmp,0,0,SRCCOPY);

dcBmp.SelectObject (pbpBmpOld);
dcBmp.DeleteDC ();

pbpMainBack->DeleteObject ();
delete pbpMainBack;
}

[Wargod2002]

OnEraseBkgnd呢