title: Strange font effect after when appending text to CEdit control
body: <p>After noticing the slowness of the interface updating, I followed the advice on <a href="https://microsoft.public.vc.mfc.narkive.com/nRKzzCIG/cedit-setwindowtext-rediculously-slow" rel="nofollow noreferrer">CEdit SetWindowText rediculously slow</a> for appending text to a CEdit control.</p>
  
  <p>Then I replaced</p>
  
  <pre><code>void CMyPropertyPage::Log(const CString&amp; sLog)
  {
      CString str;
      m_cLogEdit.GetWindowText(str);
  
      if (!str.IsEmpty())
          str += _T("\r\n");
  
      str += sLog;
  
      m_cLogEdit.SetWindowText(str);
      m_cLogEdit.LineScroll(m_cLogEdit.GetLineCount());
  }
  </code></pre>
  
  <p>by </p>
  
  <pre><code>void CMyPropertyPage::Log(const CString&amp; sLog)
  {
      m_cLogEdit.SetSel(-1,-1);
      m_cLogEdit.ReplaceSel(sLog + L"\r\n");
  
      //m_cLogEdit.LineScroll(m_cLogEdit.GetLineCount());
  
      UpdateData(FALSE);
      UpdateWindow();
  }
  </code></pre>
  
  <p>Now, when I run it, I notice a strange font blurring, as it is visible in the first two lines of the Log text box in the image. </p>
  
  <p>What is the cause and how can I fix it?</p>
  
  <p><a href="https://i.stack.imgur.com/y9atU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/y9atU.png" alt="enter image description here"></a></p>