🚀 go-pugleaf

shiva@well.sf.ca.us (Kenneth Porter) writes:
: Just what are the relationship of the various window shutdown
: messages?
: 
: What should a window do to shut itself down without shutting down its
: parent?  WinDestroyWindow(hwndSelf)? Which message should handle saving
: the window's state, WM_CLOSE or WM_DESTROY?
: 
: My current understanding is that the client window proc should process
: WM_CLOSE by invoking WinDestroyWindow() on its frame, and then return 0.
: Any resource deallocation or state-saving is done while processing
: WM_DESTROY.
: 
: Ken

Do not rely on any but WM_DESTROY message. This message is guaranteed to
be received by your window BEFORE it is actually destroyed (or at the start
of the destruction process). This is where all of your saving and other
cleanup should be done. The window IS destroyed after the message is 
processed, and you cannot do anything about it.

WM_CLOSE is passed to the FRAME window if the user selects the Close
menu item from the system menu. What you do with the message is
your affair. If you do not process this message, the frame window will
get a WM_QUIT message and effectively end. You WILL get the WM_DESTROY
message before the window is destroyed.

You can stop the end of processing by intercepting the WM_CLOSE message
and not passing it onto the default window procedure.

WM_QUIT message should be sent to the window either in response to the
WM_CLOSE message or to shut down the message reading queue. The result
of this message is the termination of processing by the WinGetMsg()
function.

The usual scenario is:
	WM_DESTROY	you are being destroyed and there is nothing
			you can do about it any more
			this message is guaranteed
	WM_CLOSE	you have a choice of either refusing to
			shut your application down or of allowing
			the application to proceed (this message
			is not guaranteed before the window is gone)
	WM_QUIT		you are being notified that the application
			or the system is about to end. You can ether
			destroy the message queue yourself, let the
			system do it for you or refuse to quit or
			this message is not guaranteed
			to continue with the shutdown
-- 
Greg Altman grega@netcom.com