MFC MDI: How to change the background of the MDI main frame?

[ovidiucucu]

Q: How can I change the background of the MDI main frame?

A: In fact, on the main frame background lies another window of 'MDIClient' class. So do the following:

• Using ClassWizard, add a generic CWnd-derived class, let's say it CMDIClientWnd
  
  
  
• Add a member of type CMDIClientWnd to CMainFrame class
  
  

  class CMainFrame : public CMDIFrameWnd
  {
  // ...
  // Attributes
  protected:
     CMDIClientWnd m_wndMDIClient;
  // ...
  };

• In CMainFrame::OnCreate subclass the MDI client window
  
  

  int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
  {
     if (CMDIFrameWnd::OnCreate(lpCreateStruct) == -1)
        return -1;
     // NOTE: m_hWndMDIClient is a public member of CMDIFrameWnd
     m_wndMDIClient.SubclassWindow(m_hWndMDIClient);
  // ...
  }

• Add a member of type CBrush to class CMDIClientWnd
  
  

  class CMDIClientWnd : public CWnd
  {
  // Attributes
  protected:
     CBrush  m_brush; // will be used to fill the backgound
  };

• Create the brush in CMDIClientWnd constructor
  
  

  CMDIClientWnd::CMDIClientWnd()
  {
     // this example uses a pattern brush filled from a bitmap resource
     CBitmap bitmap;
     bitmap.LoadBitmap(IDB_FISHING);
     m_brush.CreatePatternBrush(&bitmap);
  }

• Finally, handle 'WM_ERASEBKGND'
  
  

  BOOL CMDIClientWnd::OnEraseBkgnd(CDC* pDC) 
  {
     CBrush* pbrushOld = pDC->SelectObject(&m_brush);
     CRect rect;
     pDC->GetClipBox(&rect);
     pDC->PatBlt(rect.left, rect.top, rect.Width(), rect.Height(), PATCOPY);
     pDC->SelectObject(pbrushOld);
  
     return TRUE;
  }