On Thu, 5 Jul 2007 16:43:26 -0700 "David Ching"
<dc@remove-this.dcsoft.com> wrote:
"Frank Cusack" <fcusack@fcusack.com> wrote in message
news:m2abuaig6h.fsf@sucksless.local...
CTrayApp::CTrayApp()
: CSingleInstanceApp(TEXT("{...}"))
{
// if this is the 2nd instance, allow the 1st instance to come to fg
if (!AllowSetForegroundWindow(ASFW_ANY))
throw 1;
}
CTrayApp theApp;
BOOL
CTrayApp::InitInstance()
{
if (!AmITheFirst()) {
// wait just a bit so ASFW() in 2nd instance works
// (don't exit before 2nd instance calls SFW())
Sleep(500);
return FALSE;
}
CMainFrame *pMainFrame = new CMainFrame;
m_pMainWnd = pMainFrame;
if (!pMainFrame->Create(NULL, "foo"))
return FALSE;
m_pMainWnd->ShowWindow(SW_HIDE);
m_pMainWnd->UpdateWindow();
return TRUE;
}
void CTrayApp::OnSecondInstance(UINT, LPARAM)
{
m_pMainWnd->SetForegroundWindow(); // no effect (but main wnd was
hidden)
AfxMessageBox("hello world!", MB_OK|MB_SETFOREGROUND); // not in fg
}
====
OK, let's start from scratch:
//////////////////////////////////////////////////////////////////////////
// Shared global variables - visible to all instances of this .exe
#pragma data_seg(".sdata")
HWND sh_hwndMainFrame = NULL;
#pragma data_seg()
// This comment makes the above data segment shareable
// It replaces having to add a linker option to the project
#pragma comment(linker, "/SECTION:.sdata,rws")
CTrayApp::CTrayApp()
: CSingleInstanceApp(TEXT("{...}"))
{
}
CTrayApp theApp;
BOOL
CTrayApp::InitInstance()
{
if (!AmITheFirst()) {
// this instance (the second instance) has the focus and must
explicity
give it away
AllowSetForegroundWindow(ASFW_ANY);
// Request the first instance to bring its window to foreground
// Post message to CMainFrame of first instance
// Assume CMainFrame::OnSecondInstance() is called when it receives a
UWM_SECOND_INSTANCE message
ASSERT (sh_hwndMainFrame != NULL);
::PostMessage ( sh_hwndMainFrame, UWM_SECOND_INSTANCE, 0, 0);
return FALSE;
}
// First instance - create mainframe window that is hidden
CMainFrame *pMainFrame = new CMainFrame;
m_pMainWnd = pMainFrame;
if (!pMainFrame->Create(NULL, "foo"))
return FALSE;
// No need to show or update the window, as it is hidden --- comment
out
//m_pMainWnd->ShowWindow(SW_HIDE);
//m_pMainWnd->UpdateWindow();
// Save main window handle for use in second instance
sh_hwndMainFrame = m_pMainWnd->GetSafeHwnd();
return TRUE;
}
Does this make sense?
It makes sense, but seems to be the same as what I'm doing.
Using the CSingleInstanceApp class I found, AmITheFirst() sends the
notification to the 1st instance. Therefore, I call ASFW() in my
constructor, so that I know it is called before the 1st instance tries
to call SFW(). In your example, AmITheFirst() would (apparently) just
return the value of (sh_hwndMainFrame == NULL).
CSingleInstanceApp creates a shared file mapping for the purpose of
sharing data between the 2 (or more?) instances. The constructor
saves the thread id into the shared space if the shared mapping
doesn't already exist; if it did already exist, it posts a message to
the thread whose id was saved. This seems to be a common technique.
It does work, as far as only allowing a single instance goes.
Why did you move ASFW() from the constructor to InitInstance()? I
guess it's better that away since only the 2nd instance will allow
focus to be taken from it, but does it make any other difference?
-frank
I didn't know CSingleInstanceApp did all that. So you're right, your code
and mine do similar. I am still confused about your call to Sleep() and why
you think you need to wait for the second instance there. In any case,
of it, since you just don't know how long to sleep for. Whatever time
correct window. There's a KnowledgeBase article on that.