How do i free memory for a HFONT object

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I have a small matter of GDI leak and i wanted to know someone's opinion on how to solve this.Say i have a class that enfolds data specific to creating and handling a window ex:

class Wnd  {
   HWND hWnd;
   HFONT hFont;
   LOGFONT LogFont;
   //etc
public:
   //constructors and member functions
   //The following function atempts to change the font of the window
   //pointed to by the hWnd parameter
   void ChangeFont (const LOGFONT& lf)  {
      std::memcpy (&LogFont,&lf,sizeof(LOGFONT));
      hFont=CreateFontIndirect (&LogFont);
      SendMessage (hWnd,WM_SETFONT,(WPARAM) hFont,(LPARAM) 1);
    }
   ~Wnd ()  {
      //i don't think this would work since i haven't used the SelectObject function
      DeleteObject ((HGDIOBJ) hFont);
    }
 };

So the main question is , at destruction time how do i release the memory allocated to the hFont parameter?Should i get a device context of the window and use the SelectObject () function so that after that i could release it calling the function for the old font and use DeleteObject () to free the memory?Thanks a lot.

Posted 26-Jul-11 9:32am

caut_baia

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3 solutions

Solution 1

The hFont memory is owned by the system and will be freed when you call DeleteObject() (or DeleteFont()). Why do you need to make a copy of the LOGFONT structure in order to create the hFont object, just use the original.

Posted 26-Jul-11 9:48am

Richard MacCutchan

Solution 2

I inherit from it and i need a member LOGFONT variable.So can i delete it in the body of the destructor ?Because i tried and the actual cleanup isn't performed properly.And thanks for the answer.

Posted 26-Jul-11 9:56am

caut_baia

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mbue · Accepted Answer · 2011-07-26T16:22:00

class Wnd
{
  HWND     hWnd;
  HFONT    hFont;
  LOGFONT  LogFont;
    //etc
public:
    //constructors and member functions
    //The following function atempts to change the font of the window
    //pointed to by the hWnd parameter
  void ChangeFont(const LOGFONT& lf)
  {
    memcpy(&LogFont,&lf,sizeof(LOGFONT));
    if(hFont) DeleteObject(hFont);
    hFont = CreateFontIndirect (&LogFont);
    SendMessage(hWnd,WM_SETFONT,(WPARAM)(hFont?hFont:GetStockObject(ANSI_VAR_FONT),(LPARAM)1);
  }
  Wnd()
  {
    hWnd  = 0;
    hFont = 0;
    // ...
  }
  ~Wnd()
  {
    //i don't think this would work since i haven't used the SelectObject function
    if(hFont) DeleteObject(hFont);
  }
};

That looks better, Regards.