Win32 API Window messages WM_CREATE
Example
A WM_CREATE message is sent to your window procedure during the window's CreateWindowEx call. The lp argument contains a pointer to a CREATESTRUCT which contains the arguments passed to CreateWindowEx. If an application returns 0 from WM_CREATE, the window is created. If an application returns -1, creation is canceled.
LRESULT CALLBACK winproc(HWND hwnd, UINT wm, WPARAM wp, LPARAM lp) { switch (wm) { case WM_CREATE: CREATESTRUCT *cs = (CREATESTRUCT *) lp; if (MessageBox(hwnd, "Do you want to continue creating the window?", "", MB_YESNO) == IDYES) { /* create window controls */ return 0; } /* cancel creation */ return -1; } return DefWindowProc(hwnd, wm, wp, lp); } 
