can someone tell me why this code doesn't work? it should prevent windows from shutdown and display a messagebox, but it doesn't work! i tried to return 0 (as you can see below) and i tried to return 1. nothing works. please help.
.386
.model flat, stdcall
option casemap: none
include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
includelib \masm32\lib\kernel32.lib
include \masm32\include\user32.inc
includelib \masm32\lib\user32.lib
.data
msgtext db "blabla",0
msgtitle db "",0
iswaiting db 1
.data?
hinstance HINSTANCE ?
aMsg MSG
.code
reminder:
invoke GetModuleHandle, NULL
mov hinstance, eax
.while iswaiting==1
invoke WaitMessage
invoke GetMessage, addr aMsg, NULL, 0, 0
.if aMsg.message==WM_QUERYENDSESSION
invoke MessageBox,NULL,addr msgtext,addr msgtitle,MB_OK or MB_ICONEXCLAMATION
mov iswaiting, 0
mov eax,0
ret
.endif
ret
.endw
invoke ExitProcess, NULL
end reminder
WM_QUERYENDMESSAGE must be handled in a window proc, because Windows is using some kind of SendMessage function to send out this message to every window in the system.
If a message handler needs to return a value to the sender via EAX, then a window proc is the only way to do it. The various SendMessage functions (which require a window destination) provide the only style of message passing that works like a subroutine call. GetMessage passes such messages directly to the window proc, bypassing all other message processing.
A dialog proc can also work because it is called by a window proc. However, you'll need to use the dialog box method of returning values.