A piece of code for a self-drawn button, why is there a memory leak?

qq3568i

Every time it runs, the memory will increase by 12 to 16 bytes. What's wrong?
Code:
void CShadowCtrl :: DrawItem (LPDRAWITEMSTRUCT lpDrawItemStruct)
{
CDC * dc = GetDC ();
dcMemory.CreateCompatibleDC (dc);
CRect rc;
GetClientRect (&rc);

CBitmap bmp;
bmp.CreateCompatibleBitmap (dc, rc.Width (), rc.Height ());
dcMemory.SelectObject (&bmp);
Ranch
CBrush brush, * oldBrush;
CPen pen, * oldPen;

// draw BK
brush.Detach ();
brush.CreateSolidBrush (m_bkColor);
pen.Detach ();
pen.CreatePen (PS_SOLID, 1, m_bkColor);
oldBrush = dcMemory.SelectObject (&brush);
oldPen = dcMemory.SelectObject (&pen);
dcMemory.Rectangle (&rc);

// Draw Text
dcMemory.SelectObject (&m_textFont);
CString strText;
GetWindowText (strText);
dcMemory.SetTextColor (m_textCurrColor);
dcMemory.SetBkMode (TRANSPARENT);
dcMemory.DrawText (strText,&rc, DT_CENTER | DT_VCENTER | DT_WORDBREAK);

dc-> BitBlt (0,0, rc.Width (), rc.Height (),&dcMemory, 0,0, SRCCOPY);
dcMemory.SelectObject (oldBrush);
dcMemory.SelectObject (oldPen);
brush.DeleteObject ();
pen.DeleteObject ();
bmp.DeleteTempMap ();
bmp.DeleteObject ();
dcMemory.DeleteDC ();
}

chris_zc

You used
CDC * dc = GetDC ();
You should add
ReleaseDC (dc);
You try again to see if it works.

afanti_007

I do n’t know what happened to the memory leak
But when I overload this function, rcItem, hwnd ... are all obtained through lpDrawItemStruct

chris_zc

A memory leak is when you apply to temporarily use the memory but not release it, especially in the ontimer event. Suppose you apply once a second so that your program should die soon.

chris_zc

E.g:
CPen * apen = new CPen; // Apply for temporary memory;
You should add
delete apen;
If not added, this is a memory leak.
I do n’t know if it ’s unreasonable to say that, I am also a rookie.

qq3568i

It ’s really a DC issue, thank you
DC with lpDrawItemStruct is fine

chris_zc

Just solve the problem, make progress slowly, we should become stronger after a long time.

深蓝旅者

you forget to restore old bmp and old font.
CDC * dc = GetDC ();
dcMemory.CreateCompatibleDC (dc);
CRect rc;
GetClientRect (&rc);
The
CBitmap bmp;
bmp.CreateCompatibleBitmap (dc, rc.Width (), rc.Height ());
CBitmap * oldBmp = dcMemory.SelectObject (&bmp);
The
CBrush brush, * oldBrush;
CPen pen, * oldPen;
The
// draw BK
// brush.Detach ();
brush.CreateSolidBrush (m_bkColor);
// pen.Detach ();
pen.CreatePen (PS_SOLID, 1, m_bkColor);
oldBrush = dcMemory.SelectObject (&brush);
oldPen = dcMemory.SelectObject (&pen);
dcMemory.Rectangle (&rc);
The
// Draw Text
CFont * oldFont = dcMemory.SelectObject (&m_textFont);
CString strText;
GetWindowText (strText);
dcMemory.SetTextColor (m_textCurrColor);
dcMemory.SetBkMode (TRANSPARENT);
dcMemory.DrawText (strText,&rc, DT_CENTER | DT_VCENTER | DT_WORDBREAK);
The
dc-> BitBlt (0,0, rc.Width (), rc.Height (),&dcMemory, 0,0, SRCCOPY);
dcMemory.SelectObject (oldBrush);
dcMemory.SelectObject (oldPen);
dcMemory.SelectObject (oldFont);
dcMemory.SelectObject (oldBmp);
brush.DeleteObject ();
pen.DeleteObject ();
// bmp.DeleteTempMap ();
bmp.DeleteObject ();
dcMemory.DeleteDC ();
ReleaseDC (dc);