In a previous article I showed how to make AfxMessageBox to display a message box with auto-close, by using a CBT hook.
One reader suggested that whould be nice if the message box displays also the time left until auto-closing. I thought that’s a very good idea and promissed an update. Here it is!

AfxMessageBox with Auto-close

Of course, may be more than one solution. I chose one which appends “Time left: xxx sec.” in the bottom of the built-in static text control. For this purpose, I added two private methods to CAutoMessageBox class:

CAutoMessageBox::_InitStaticTextCtrl – initializes the static contol: finds the static control, keeps in mind the initial text, makes space for an extra-line of text, and assigns an ID to be used later.

void CAutoMessageBox::_InitStaticTextCtrl()
{
   // search for static text control
   CWnd* pWndCtrl = GetWindow(GW_CHILD);
   while(NULL != pWndCtrl->GetSafeHwnd())
   {
      const int nMaxCount = 63;
      CString strClass;
      ::GetClassName(pWndCtrl->m_hWnd, 
         strClass.GetBufferSetLength(nMaxCount), nMaxCount);
      DWORD dwStyle = pWndCtrl->GetStyle();
      strClass.ReleaseBuffer();
      if(!strClass.CompareNoCase(_T("STATIC")) 
         && !(dwStyle & SS_ICON))
      {
         // set static control ID
         ::SetWindowLong(pWndCtrl->m_hWnd, GWL_ID, IDC_STATIC_TEXT);
         // keep in mind the initial text
         pWndCtrl->GetWindowText(m_strIntitalText);
         // calculate extra-line height and width
         CClientDC dc(this);
         CFont* pFont = pWndCtrl->GetFont();
         ASSERT(NULL != pFont);
         CFont* pOldFont = dc.SelectObject(pFont);
         CRect rcText(0, 0, 0, 0);
         dc.DrawText(CString(_T("Time left: 999 sec.")), rcText, 
            DT_SINGLELINE|DT_CALCRECT);
         dc.SelectObject(pOldFont);
         // add extra-line space
         CRect rcCtrl;
         pWndCtrl->GetWindowRect(rcCtrl);
         ScreenToClient(rcCtrl);
         rcCtrl.bottom += rcText.Height();
         const int nExtraWidth = rcText.Width() - rcCtrl.Width();
         if(nExtraWidth > 0)
            rcCtrl.right += nExtraWidth;
         pWndCtrl->MoveWindow(rcCtrl);
         break;
      }
      // get next child control
      pWndCtrl = pWndCtrl->GetWindow(GW_HWNDNEXT); 
   }
}

void CAutoMessageBox::_InitStaticTextCtrl()

{

// search for static text control

CWnd* pWndCtrl = GetWindow(GW_CHILD);

while(NULL != pWndCtrl->GetSafeHwnd())

{

const int nMaxCount = 63;

CString strClass;

::GetClassName(pWndCtrl->m_hWnd,

strClass.GetBufferSetLength(nMaxCount), nMaxCount);

DWORD dwStyle = pWndCtrl->GetStyle();

strClass.ReleaseBuffer();

if(!strClass.CompareNoCase(_T("STATIC"))

&& !(dwStyle & SS_ICON))

{

// set static control ID

::SetWindowLong(pWndCtrl->m_hWnd, GWL_ID, IDC_STATIC_TEXT);

// keep in mind the initial text

pWndCtrl->GetWindowText(m_strIntitalText);

// calculate extra-line height and width

CClientDC dc(this);

CFont* pFont = pWndCtrl->GetFont();

ASSERT(NULL != pFont);

CFont* pOldFont = dc.SelectObject(pFont);

CRect rcText(0, 0, 0, 0);

dc.DrawText(CString(_T("Time left: 999 sec.")), rcText,

DT_SINGLELINE|DT_CALCRECT);

dc.SelectObject(pOldFont);

// add extra-line space

CRect rcCtrl;

pWndCtrl->GetWindowRect(rcCtrl);

ScreenToClient(rcCtrl);

rcCtrl.bottom += rcText.Height();

const int nExtraWidth = rcText.Width() - rcCtrl.Width();

if(nExtraWidth > 0)

rcCtrl.right += nExtraWidth;

pWndCtrl->MoveWindow(rcCtrl);

break;

}

// get next child control

pWndCtrl = pWndCtrl->GetWindow(GW_HWNDNEXT);

}

CAutoMessageBox::_SetStaticTextCtrl – sets the text which contains time left.

void CAutoMessageBox::_SetStaticTextCtrl()
{
   UINT nRemained = (m_nTimeOut - m_nElapsed) / 1000 + 1;
   CWnd* pWndStatic = GetDlgItem(IDC_STATIC_TEXT);
   ASSERT(NULL != pWndStatic->GetSafeHwnd());

   CString strText;
   strText.Format(_T("%s\nTime left: %u sec."), 
      m_strIntitalText, nRemained);
   pWndStatic->SetWindowText(strText);
}

void CAutoMessageBox::_SetStaticTextCtrl()

{

UINT nRemained = (m_nTimeOut - m_nElapsed) / 1000 + 1;

CWnd* pWndStatic = GetDlgItem(IDC_STATIC_TEXT);

ASSERT(NULL != pWndStatic->GetSafeHwnd());

CString strText;

strText.Format(_T("%s\nTime left: %u sec."),

m_strIntitalText, nRemained);

pWndStatic->SetWindowText(strText);

}

For more implementation details of CAutoMessageBox class, download and have a look in the attached demo project.

Downloads

AfxMessageBox_with_auto_close (updated).zip (804)

Introduction

This article describes how to make the MFC function AfxMessageBox to dispay a message box that is automatically dismissed after a given time.

For that purpose we can do the following:

Override CWinApp::DoMessageBox virtual function for customzing the default AfxMessageBox.
Set a CBT hook to catch the message box creation.
In the CBT hook procedure, subclass the message box window procedure.
In the message box procedure, handle WM_INITDIALOG message and set a timer.
Handle WM_TIMER to automatically close the message box.

Next are simplified code snippets that show how to implement the steps described above. CAutoMessageBox is a class designed to implement the message box with auto-close (sets CBT hook, subclasses the message box and so on).
More detailed code can be found in the demo application attached at the end of the article.

1. Override CWinApp::DoMessageBox

int CDemoApp::DoMessageBox(LPCTSTR lpszPrompt, UINT nType, UINT nIDPrompt) 
{
   CAutoMessageBox msgBox;

   if(MB_TIMED & nType)
   {
      // ...
       VERIFY(msgBox.Hook(nTimeOut, bShowProgress));
      // ...
   }
   // call base class method for doing the default work.
   return CWinApp::DoMessageBox(lpszPrompt, nType, nIDPrompt);
}

int CDemoApp::DoMessageBox(LPCTSTR lpszPrompt, UINT nType, UINT nIDPrompt)

{

CAutoMessageBox msgBox;

if(MB_TIMED & nType)

{

// ...

VERIFY(msgBox.Hook(nTimeOut, bShowProgress));

// ...

}

// call base class method for doing the default work.

return CWinApp::DoMessageBox(lpszPrompt, nType, nIDPrompt);

}

2. Set the CBT hook

BOOL CAutoMessageBox::Hook(UINT nTimeOut, BOOL bShowProgress)
{
   // ...
   DWORD dwThreadID = ::GetCurrentThreadId();
   HINSTANCE hInstance = AfxGetInstanceHandle();

   m_hHook = ::SetWindowsHookEx(WH_CBT, &CAutoMessageBox::HookProc, hInstance, dwThreadID);

   return m_hHook != NULL;
}

BOOL CAutoMessageBox::Hook(UINT nTimeOut, BOOL bShowProgress)

{

// ...

DWORD dwThreadID = ::GetCurrentThreadId();

HINSTANCE hInstance = AfxGetInstanceHandle();

m_hHook = ::SetWindowsHookEx(WH_CBT, &CAutoMessageBox::HookProc, hInstance, dwThreadID);

return m_hHook != NULL;

}

3. Subclass the message box window procedure

LRESULT CALLBACK CAutoMessageBox::HookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
   switch(nCode)
   {
   case HCBT_CREATEWND: // a window is about to be created
      {
         LPCBT_CREATEWND lpCbtCreate = (LPCBT_CREATEWND)lParam;
         HWND hWnd = (HWND)wParam;

         if(WC_DIALOG == lpCbtCreate->lpcs->lpszClass && m_pWndThis->GetSafeHwnd() == NULL)
         {
            // Keep in mind the message box handle to subclass it later
            m_hWndThis = hWnd;
         }
         else if(NULL != m_hWndThis && NULL == m_pWndThis->GetSafeHwnd())
         {
            m_pWndThis->SubclassWindow(m_hWndThis);
         }
      }
      break;
   case HCBT_DESTROYWND: // a window is about to be destroyed
      {
         if(m_pWndThis->GetSafeHwnd() == (HWND)wParam) // it's our messge box
         {
            // so set back its default procedure
            m_pWndThis->UnsubclassWindow();
         }
      }
      break;
   }
   return ::CallNextHookEx(m_hHook, nCode, wParam, lParam);
}

LRESULT CALLBACK CAutoMessageBox::HookProc(int nCode, WPARAM wParam, LPARAM lParam)

{

switch(nCode)

{

case HCBT_CREATEWND: // a window is about to be created

{

LPCBT_CREATEWND lpCbtCreate = (LPCBT_CREATEWND)lParam;

HWND hWnd = (HWND)wParam;

if(WC_DIALOG == lpCbtCreate->lpcs->lpszClass && m_pWndThis->GetSafeHwnd() == NULL)

{

// Keep in mind the message box handle to subclass it later

m_hWndThis = hWnd;

}

else if(NULL != m_hWndThis && NULL == m_pWndThis->GetSafeHwnd())

{

m_pWndThis->SubclassWindow(m_hWndThis);

}

break;

case HCBT_DESTROYWND: // a window is about to be destroyed

{

if(m_pWndThis->GetSafeHwnd() == (HWND)wParam) // it's our messge box

{

// so set back its default procedure

m_pWndThis->UnsubclassWindow();

}

break;

}

return ::CallNextHookEx(m_hHook, nCode, wParam, lParam);

}

4. Handle WM_INITDIALOG and set a timer

LRESULT CAutoMessageBox::OnInitDialog(WPARAM wParam, LPARAM lParam)
{
   if(m_nTimeOut > 0)
   {
      SetTimer(0, m_nTimerStep, NULL);
   }
   // ...
   return TRUE;
}

LRESULT CAutoMessageBox::OnInitDialog(WPARAM wParam, LPARAM lParam)

{

if(m_nTimeOut > 0)

{

SetTimer(0, m_nTimerStep, NULL);

}

// ...

return TRUE;

}

5. Handle WM_TIMER and close the message box

void CAutoMessageBox::OnTimer(UINT nIDEvent) 
{
   m_nElapsed += m_nTimerStep;
   // ...
   if(m_nElapsed >= m_nTimeOut)
   {
      KillTimer(0);
      EndDialog(IDTIMEOUT);
   }
}

void CAutoMessageBox::OnTimer(UINT nIDEvent)

{

m_nElapsed += m_nTimerStep;

// ...

if(m_nElapsed >= m_nTimeOut)

{

KillTimer(0);

EndDialog(IDTIMEOUT);

}

Demo application

You can find attached here a simple dialog-based application for demo purpose.

Just choose the options (time out, message box style and so on) then click “Say Hello!” button. If “Auto close” is checked, a message box with time-out will be shown.

Resources

Downloads

AfxMessageBox_with__auto_close.zip (930)

codexpert blog

I see native code

Tag Archives: CBT Hook

AfxMessageBox with Auto-close – Part 2

See also

Downloads

Like this:

AfxMessageBox with Auto-close

Introduction

1. Override CWinApp::DoMessageBox

2. Set the CBT hook

3. Subclass the message box window procedure

4. Handle WM_INITDIALOG and set a timer

5. Handle WM_TIMER and close the message box

Demo application

Resources

See also

Downloads

Like this:

See also

Downloads

Share this:

Like this:

Introduction

1. Override CWinApp::DoMessageBox

2. Set the CBT hook

3. Subclass the message box window procedure

4. Handle WM_INITDIALOG and set a timer

5. Handle WM_TIMER and close the message box

Demo application

Resources

See also

Downloads

Share this:

Like this: