Create a Modeless Dialog Box as Sibling of the App's Main Window






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Nov 10, 2000

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Simple step by step article explaining how to create a modeless dialog box as sibling of the app's main window.
This article is part of the drag and drop interface samples.
- Serializing ASCII Data
- Modeless child dialog
- Modeless sibling dialog
- The drag source
- The MFC drop target
- The TBTextTarget class
It's nearly as short as the child version of modeless dialogs.
Follow these steps:
- Create a new dialog resource and use the Class Wizard for making a new
CDialog
based classCOtherDropDialog
. - In the class maintaining the modeless dialog (here it's
CInterfaceView
), add a member variable of type pointer toCWinThread
and make sure you have a destructor:class CInterfaceView : public CView { ... CWinThread *m_pDlgThread ~CInterfaceView(); ... }
- Use
ClassWizard
to create a newCWinThread
-based classCOtherDropDialogThread
. - Override
COtherRopDialogThread::InitInstance()
:
If you forget to change them_pMainWnd
variable, the dialog will stay modal!BOOL COtherDropDialogThread::InitInstance() { COtherDropDialog dlg; m_pMainWnd = &dlg; dlg.DoModal(); // returning false will make MFC doing the cleanup for us :) return FALSE; }
- In your appropriate message handler, do the following:
void CInterfaceView::OnFileOthermodeless() { // this block determines if we have our dialog already // displayed and not yet closed. You can't rely on // m_pDlgThread to be NULL, because if you already have displayed // and closed it, the pointer is not NULL but invalid if (AfxIsValidAddress(m_pDlgThread, sizeof(CWinThread)) && AfxIsValidAddress(m_pDlgThread->m_pMainWnd, sizeof(CWnd))) { if (::IsWindow(m_pDlgThread->m_pMainWnd->GetSafeHwnd())) { m_pDlgThread->GetMainWnd()->SetWindowPos( &wndTop, 0,0,0,0,SWP_NOMOVE|SWP_NOSIZE|SWP_SHOWWINDOW); return; } } // OK, we need to create a new thread m_pDlgThread=AfxBeginThread( RUNTIME_CLASS(COtherDropDialogThread) ); }
- If you like your top-level window to have an icon displayed in the taskbar, add the following to
COtherDropDialog:: OnInitDialog
(omitted in the sample):BOOL COtherDropDialog::OnInitDialog() { CDialog::OnInitDialog(); m_hIcon = AfxGetApp()->LoadIcon(IDI_MYICON); SetIcon(m_hIcon, TRUE); SetIcon(m_hIcon, FALSE); // and all the other stuff //... }
- Don't forget to do the clean-up in the destructor:
CInterfaceView::~CInterfaceView() { if (AfxIsValidAddress(m_pDlgThread, sizeof(CWinThread)) && AfxIsValidAddress(m_pDlgThread->m_pMainWnd, sizeof(CWnd))) { // retrieve the threads main window CDialog *pDlg = (CDialog *)m_pDlgThread->m_pMainWnd; if (::IsWindow(pDlg->GetSafeHwnd())) { // make sure we have a CDialog-derived main // thread window then terminate it ASSERT(pDlg->IsKindOf(RUNTIME_CLASS(CDialog))); pDlg->EndDialog(IDCANCEL); // now give the thread some time to end, // 2 second should be enough. You may // able to use INFINITE as wait value, if you dare... WaitForSingleObject(m_pDlgThread->m_hThread, 2000); m_pDlgThread=NULL; } } }
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