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Need some info and help with ReleaseDC(pDC)

Posted on 2007-11-21
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Last Modified: 2013-11-20
Please take a look at my code below.
It works just fine to change the font of a column in a ListView.
I allways learned that you have to release the DC when your are done.

             HDC hdc = pLVCD->nmcd.hdc;
             CDC* pDC=NULL;

When I add the ReleaseDC(pDC) in OnCustomdrawList, the programm will not show the new font.
Should I be concerned about the Release??? Or where can I add the Release???
Please let me know.

Thank You.

Best regards,
Thomas... a beginner with MFC

             

//----------------------------------------------------------------------------
 void CThyssenSchulteDialog::OnCustomdrawList(NMHDR* pNMHDR, LRESULT* pResult)
 {
       NMLVCUSTOMDRAW* pLVCD = reinterpret_cast<NMLVCUSTOMDRAW*>( pNMHDR );

       // Take the default processing unless we set this to something else below.
    *pResult = 0;
      
    // First thing - check the draw stage. If it's the control's prepaint
    // stage, then tell Windows we want messages for every item.

    if ( CDDS_PREPAINT == pLVCD->nmcd.dwDrawStage )
        {
          *pResult = CDRF_NOTIFYITEMDRAW;
            }
    else if ( CDDS_ITEMPREPAINT == pLVCD->nmcd.dwDrawStage )
        {
        // This is the notification message for an item.  We'll request
        // notifications before each subitem's prepaint stage.

        *pResult = CDRF_NOTIFYSUBITEMDRAW;
        }
    else if ( (CDDS_ITEMPREPAINT | CDDS_SUBITEM) == pLVCD->nmcd.dwDrawStage )
        {
        // This is the prepaint stage for a subitem. Here's where we set the
        // item's text and background colors. Our return value will tell
        // Windows to draw the subitem itself, but it will use the new colors
        // we set here.
           
            COLORREF crText, crBkgnd;
            int iCol = pLVCD->iSubItem;
            int iRow = pLVCD->nmcd.dwItemSpec;

            CString str=m_List.GetItemText(iRow,4);
                  
            
            //------------ Sichere vorherige Schrift -----------
              CFont *oldfont = GetFont();
            //--------------- Erstelle neue Schrift ------------
             CString my_new_font="Bradley Hand ITC";

              CFont *fontPtr = new CFont();
              fontPtr->CreateFont(
              12,
               0,
               0,
               0,
               FW_SEMIBOLD,
               0,
               0,
               0,
               DEFAULT_CHARSET,
               OUT_CHARACTER_PRECIS,
               CLIP_CHARACTER_PRECIS,
               DEFAULT_QUALITY,
               DEFAULT_PITCH|FF_DONTCARE,my_new_font);
             //------------------------------------------------
      
                 //========================
                   HDC hdc = pLVCD->nmcd.hdc;
                   CDC* pDC=NULL;
                  //CDC* pDC =CDC::FromHandle(pLVCD->nmcd.hdc);
                 //========================

               if (3== pLVCD->iSubItem )
           {
                   crText = RGB(255,165,0);   //orange
                   crBkgnd = RGB(255,255,224); //beige
            //------------ Neue Schrift -----------
                   if(!pDC) pDC = CDC::FromHandle(hdc);
                   pDC->SelectObject(fontPtr);
            //-------------------------------------

               }
           else
               {
                    
                      crText = RGB(0,0,255);      //blau
                      crBkgnd = RGB(255,255,224); //beige
                     //---------- Alte Schrift -------------
                      if(!pDC) pDC = CDC::FromHandle(hdc);
                      pDC->SelectObject(oldfont);
                     //-------------------------------------
                         
                  }
               
             
               
            
       

        // Store the colors back in the NMLVCUSTOMDRAW struct.
        pLVCD->clrText = crText;
        pLVCD->clrTextBk = crBkgnd;

        // Tell Windows to paint the control itself.
           *pResult = CDRF_DODEFAULT;
               
             
        }
}
0
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Question by:tsp2002
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4 Comments
 
LVL 19

Expert Comment

by:alb66
ID: 20333970
In the code you posted there is no call to ReleaseDC(); where do you call it?
0
 

Author Comment

by:tsp2002
ID: 20334029
I tried it here....

 // Store the colors back in the NMLVCUSTOMDRAW struct.
        pLVCD->clrText = crText;
        pLVCD->clrTextBk = crBkgnd;

        // Tell Windows to paint the control itself.
           *pResult = CDRF_DODEFAULT;
            ReleaseDC();
        }
}
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LVL 19

Accepted Solution

by:
alb66 earned 500 total points
ID: 20334223
An application must call ReleaseDC() only if it has called GetWindowDC() or GetDC() in order to retrieve the DC.
See http://msdn2.microsoft.com/en-us/library/ms533251.aspx
0
 

Author Comment

by:tsp2002
ID: 20334349
....An application must call ReleaseDC() only if it has called GetWindowDC() or GetDC() in order to retrieve the DC.

Thanks...that was the information I need. I thought I have to use ReleaseDC for any DC
Thanks for your help.
Best regards,
Thomas

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