[MFC] Cum punem o imagine in zona MDI client?

[Ovidiu Cucu]

Intrebare
Cum punem o imagine in zona client a unui frame MDI?

Image in MDI client.jpg (19.16 KiB) Viewed 8694 times

Rezolvare
Pe fundalul (zona client) unui frame MDI se afla o fereastra al carui handle este pastrat intr-un membru public al clasei CMDIFrameWnd, m_hWndMDIClient. Daca subclasam aceasta fereastra intr-o clasa pe care o definim noi, atunci putem customiza zona MDI client, inclusiv sa pictam o imagine.

Pasii de urmat ar fi urmatorii:

1. Definim o clasa derivata din CWnd, si-i zicem CMDIClientWnd.
2. In CMainFrame adaugam un membru de tip CMDIClientWnd, m_wndMDIClient.

   Code: Select all

   #include "MDIClientWnd.h"
   
   class CMainFrame : public CMDIFrameWnd
   {
      CMDIClientWnd m_wndMDIClient;
   // ...
   };

3. In CMainFrame::OnCreate subclasam ferastra MDI client lui CMDIClientWnd.

   Code: Select all

   int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
   {
      // ...
      // NOTE: m_hWndMDIClient is a public member of CMDIFrameWnd
      m_wndMDIClient.SubclassWindow(m_hWndMDIClient);
      // ...
      return 0;
   }

4. In hadlerul din CMDIClientWnd al mesajului WM_PAINT, desenam imaginea dorita.
   Exemplu

   Code: Select all

   void CMDIClientWnd::OnPaint() 
   {
      CPaintDC dc(this);
      CRect rcClient;
      GetClientRect(rcClient);
   
      CDC dcMem1; // memory DC for double buffering
      dcMem1.CreateCompatibleDC(&dc);
      CBitmap bitmap1;
      bitmap1.CreateCompatibleBitmap(&dc, rcClient.Width(), rcClient.Height());
      CBitmap* pOldBitmap1 = dcMem1.SelectObject(&bitmap1);
      // fill memory device context with the desired brush
      // COLOR_APPWORKSPACE is for default MDI client color
      CBrush backBrush;
      backBrush.CreateSolidBrush(::GetSysColor(COLOR_APPWORKSPACE));
      dcMem1.FillRect(rcClient, &backBrush);
   
      CDC dcMem2; // memory DC for the bitmap to draw
      dcMem2.CreateCompatibleDC(&dc);
      CBitmap bitmap2;
      bitmap2.LoadBitmap(IDB_LOGO);
      CBitmap* pOldBitmap2 = dcMem2.SelectObject(&bitmap2);
   
      BITMAP bmp;
      bitmap2.GetBitmap(&bmp);
      int nWidth  = bmp.bmWidth;
      int nHeight = bmp.bmHeight;
      // NOTE: place the picture in bootom-left side;
      //       you may place the picture in any other place.
      int x       = rcClient.left + 10;
      int y       = rcClient.bottom - bmp.bmHeight - 10;
      // copy the bitmap in memory device context 
      dcMem1.BitBlt(x, y, nWidth, nHeight, &dcMem2, 0, 0, SRCCOPY);
   
      CRect rcClip;
      dc.GetClipBox(rcClip);
   
      nWidth  = rcClip.Width();
      nHeight = rcClip.Height();
      x       = rcClip.left;
      y       = rcClip.top;
      // copy memory device context in client device context
      dc.BitBlt(x, y, nWidth, nHeight, &dcMem1, x, y, SRCCOPY); 
   
      dcMem1.SelectObject(pOldBitmap1);
      dcMem2.SelectObject(pOldBitmap2);
   }

5. Pe WM_SIZE, invalidam zona client pentru a forta redesenarea.

   Code: Select all

   void CMDIClientWnd::OnSize(UINT nType, int cx, int cy) 
   {
      CWnd::OnSize(nType, cx, cy);
      Invalidate();
   }

6. In fine, pentru a evita flicker-ul atunci cand se face resize, tratam WM_ERASEBKGND si intoarcem FALSE.

   Code: Select all

   BOOL CMDIClientWnd::OnEraseBkgnd(CDC* pDC) 
   {	
      return FALSE;
   }

Vezi si

• [MFC] Cum punem o imagine in toolbar?
• [MFC] Cum punem o imagine in statusbar?

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[Ovidiu Cucu]

In cazul cand clasa frame-ului este derivata din CMDIFrameWndEx, simplu si eficient este sa se suprascrie functia virtuala CMDIFrameWndEx::OnEraseMDIClientBackground.

Exemplu

Code: Select all

// MainFrm.h

class CMainFrame : public CMDIFrameWndEx
{
   // ...
   // Overrides
public:
   virtual BOOL OnEraseMDIClientBackground(CDC* pDC);
   // ...
};

Code: Select all

// MainFrm.cpp

BOOL CMainFrame::OnEraseMDIClientBackground(CDC* pDC)
{
   CRect rcClient;
   GetClientRect(rcClient);

   // draw background 
   CBrush* pOldBrush = pDC->SelectObject(&m_brushMDIBack);
   pDC->PatBlt(0, 0, rcClient.right, rcClient.bottom, PATCOPY);

   // draw logo
   CDC dcMem;
   dcMem.CreateCompatibleDC(pDC);
   BITMAP bmp;
   m_bmpSiteLogo.GetBitmap(&bmp);
   CBitmap* pOldBitmap = dcMem.SelectObject(&m_bmpSiteLogo);
   pDC->BitBlt(5, 5, bmp.bmWidth, bmp.bmHeight, &dcMem, 0, 0, SRCCOPY);

   // free GDI objects
   pDC->SelectObject(pOldBrush);
   pDC->SelectObject(pOldBitmap);

   // let CMFCVisualManager doing its job
   CMFCVisualManager::GetInstance()->OnEraseMDIClientArea(pDC, rcClient);

   return TRUE; // no further default processing
}

Alte amanunte cat si un proiect demo, gasiti pe codexpert blog: Custom Paint in MDI Client