PostQuitMessage function

?? what happend to the "add community" editor?? All linefeeds are removed and the markup functions are gone to indicate code...

If the WM_CREATE of your window fails with -1 and then does a PostQuitMessage from its WM_DESTROY then it is impossible anymore to create any other window like for instance a MessageBox. This has been tested on W2K, XP and Win7 Why? dunno. You need to keep an indicator not to call PostQuitMessage if your WM_CREATE fails. Example to demostrate this. Like this code is the messagebox does not get displayed and returns immediately with IDOK. If you remove the PostQuitMessage the messagebox gets displayed --- LRESULT CALLBACK TestWndProc ( HWND in_hWnd, UINT in_uMsg, WPARAM in_wParam, LPARAM in_lParam ) { // which message? switch (in_uMsg) { // the test case: let it fail case WM_CREATE: return -1; // then post quit message case WM_DESTROY: PostQuitMessage(0); break; } // default processing return DefWindowProc(in_hWnd, in_uMsg, in_wParam, in_lParam); } VOID TestFailWnd(VOID) { /* locals */ HWND lv_hWnd; WNDCLASS lv_WndClass; // register the class memset(&lv_WndClass, 0, sizeof(WNDCLASS)); lv_WndClass.style = CS_DBLCLKS; lv_WndClass.lpfnWndProc = TestWndProc; lv_WndClass.hInstance = GetModuleHandle(0); lv_WndClass.hIcon = LoadIcon(0, IDI_APPLICATION); lv_WndClass.hCursor = LoadCursor(NULL, IDC_ARROW); lv_WndClass.lpszClassName = TEXT("CLASSXX"); RegisterClass(&lv_WndClass); // create window lv_hWnd = CreateWindowEx( 0, TEXT("CLASSXX"), "ABC", WS_MINIMIZEBOX | WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_CAPTION, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, 0, 0, GetModuleHandle(0), NULL); // result is NULL printf("lv_hWnd=%08X\n", lv_hWnd); // this is the problem: the messagebox will not get displayed because of the // WM_CREATE failed with -1 and the PostQuitMessage in WM_DESTROY MessageBox(0,"ABC","ABC",0); // halt the app printf("DONE\n"); getchar(); } void main(void) { TestFailWnd(); }

Sorry, EVHClarity, but setting the local variable hwnd in the WndProc to NULL will change nothing to the message loop's variables and structures, unless you make it a global variable (which it is not, in the code you posted). There must be more to it in your code. Or does it effect the DefWndProc call parameter after your WM_CLOSE processing?

PostQuitMessage is used after the window has been destroyed (case WM_DESTROY) making the handle invalid for GetMessage. You can see this by catching the last error after running GetMessage:

MSG msgs = { };
int catcherror;
while((catcherror = GetMessageW(&msgs, swhandle, 0, 0)) != 0)
{
  if(catcherror == -1)
    return msgs.message;
  TranslateMessage(&msgs);
  DispatchMessage(&msgs);
} // Take a look at the exit value output at the end of execution.

You can avoid the stall by assigning a null value to the variable storing the destroyed windows handle:


LRESULT CALLBACK WinProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam)
{
switch(message)
{
  case(WM_DESTROY):
  hwnd = NULL;
  PostQuitMessage(0);
  ...

GetMessage will then pick up any messages in the thread. :-)