TimerProc in c isn't working? - c

Question

I'm trying to write a callback for my timer. I defined the TimerProc like this:
void CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT idEvent, DWORD dwTime)
{
//body of callback
}
and then the SetTimer defined like this:
myTimer = SetTimer(NULL,Timer_ID,30000,TimerProc);
my problem is that the callback never being called once the time elpassed (30 sec).
thank's for help.

Answer 1

SetTimer works by sending a WM_TIMER message to the default window procedure. Hence, as the MSDN states:
When you specify a TimerProc callback function, the default window procedure calls the callback function when it processes WM_TIMER. Therefore, you need to dispatch messages in the calling thread, even when you use TimerProc instead of processing WM_TIMER.
So make sure that you have a Message Loop running.

Answer 2

Quick test code. Works fine for me.
#include <windows.h>
static const TCHAR gc_szClassName[] = TEXT("Test");
static const TCHAR gc_szWindowTitle[] = TEXT("Test");
#define IDT_TIMER 0x100
VOID CALLBACK TimerProc(HWND hWnd, UINT uMessage, UINT_PTR uEventId, DWORD dwTime)
{
// display a message box to see the results of our beautiful program
MessageBox(hWnd, TEXT("This should pop up every 10 seconds.."), TEXT("Yay!"), MB_OK | MB_ICONINFORMATION);
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMessage, WPARAM wParam, LPARAM lParam)
{
switch (uMessage)
{
case WM_CREATE:
// run every 10 seconds
SetTimer(hWnd, IDT_TIMER, 10000, TimerPRoc);
break;
case WM_CLOSE:
DestroyWindow(hWnd);
break;
case WM_DESTROY:
KillTimer(hWnd, IDT_TIMER);
PostQuitMessage(EXIT_SUCCESS);
break;
}
return DefWindowProc(hWnd, uMessage, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpszCommandLine, int nShowCommand)
{
// define variables
HWND hWnd;
WNDCLASS wc;
MSG msg;
// unused parameters
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpszCommandLine);
UNREFERENCED_PARAMETER(nShowCommand);
// initialize WNDCLASS structure
ZeroMemory(&wc, sizeof(wc));
wc.lpfnWndProc = WndProc;
wc.hInstance = hInstance;
wc.lpszClassName = gc_szClassName;
// attempt to register the class
if (RegisterClass(&wc) != 0)
{
// attempt to create the window
hWnd = CreateWindow(gc_szClassName, gc_szWindowTitle, 0, 0, 0, 0, 0, HWND_MESSAGE, NULL, hInstance, NULL);
if (hWnd != NULL)
{
// retrieve messages
while (GetMessage(&msg, NULL, 0, 0) > 0)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
// use the return-code from the window
return (int)msg.wParam;
}
}
return EXIT_FAILURE;
}