Can't Remove WM_TIMER message - c++

Question

I have a problem with my code, and after several hours, I can't seem to figure it out...
Problem: I'm trying to attempt to connect to a server every ten seconds. When the timer first elapses, the callback function is called just fine, but then it is called again immediately (without waiting ten seconds), and it keeps being called again and again and again repeatedly, as if the timer message is not getting removed from the queue. Can anyone help?
The timer is set here:
SConnect::SConnect()
{
hSimConnect = NULL;
Attempt();
SetTimer(hMainWindow, reinterpret_cast<UINT_PTR>(this), 10000, (TIMERPROC)TimerProc);
}
The (only) application message loop is here:
while (true)
{
PeekMessage(&msg, NULL, 0, 0, PM_REMOVE);
if (msg.message == WM_QUIT)
break;
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
//UPDATES
pSCObj->Update();
manager.Update();
Sleep(50);
}
And the timer callback function is here:
void CALLBACK SConnect::TimerProc(HWND hWnd, UINT uMsg, UINT_PTR idEvent, DWORD dwTime){
SConnect *pSC = reinterpret_cast<SConnect *>(idEvent);
MSG wMsg;
if (!pSC->connected)
pSC->Attempt();
else{
pSC->connected = false;
}
}
I really appreciate any help... Please let me know if you need more info...
Sincerely,
Farley

Answer 1

I think this is happening because you are calling PeekMessage() in your message loop instead of GetMessage().
PeekMessage() will return FALSE if there are no messages in the queue. I don't know what the implementation of PeekMessage() is, but I could see it leaving the contents of the msg parameter alone if there are no messages in the queue. This means that when PeekMessage() returns FALSE, msg will contain the previous message in the queue. msg is then blindly passed to DispatchMessage(), which then dutifully will pass that to your window's window procedure. So as long as the WM_TIMER message is the last processed message, your timer callback will be called until another message is added to the queue.
You can fix this by using a more traditional message loop:
BOOL bRet;
while( (bRet = GetMessage( &msg, nullptr, 0, 0 )) != 0)
{
if (bRet == -1)
{
// handle the error and possibly exit
}
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
pSCObj->Update();
manager.Update();
}
(Message loop adapted from the sample in the GetMessage() documentation.)
Since GetMessage() will block until there is a message in the queue, you don't need to call Sleep(), and your process will not use any CPU when there is nothing for it to do.

Answer 2

Problem is that the return value of PeekMessage() is not checked. On each loop, if there is no new message, PeekMessage leaves the contents of msg unchanged, and it is simply dispatched again.
Dispatching the messages only when PeekMessage() returns true fixes the problem:
while (true)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)){
if (msg.message == WM_QUIT)
break;
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
//UPDATES
pSCObj->Update();
manager.Update();
Sleep(50);
}