Re: MFC SplashScreen Issue: Sleep in main application

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 29 Mar 2007 18:16:16 -0400

Message-ID:

<#DmoW$kcHHA.4624@TK2MSFTNGP03.phx.gbl>

giemer wrote:

Basically, I went to write up a general purpose splash screen class
for my company to be used on outgoing products that would require one.

I think I followed the main stream format, create a subclass of
CWinThread to run the Splash, and create subclasses of CWnd to display
the Splash. Additionally I created another subclass of CWnd to act as
object that can be manipulated for the splash screen (dynamic graphics
and what not), to be used in addition to just your straight throwing
bitmaps around.

Everything went as smooth as silk until I started throwing sleep
operations into the main program that would run the splash. It seems
all windows messaging seems to cease activation when that happens,
including messages in the Splash thread (and threads spawned by the
splash thread, these are your generic UINT Thread(LPVOID) worker
threads though).

In short, anytime I use one of those CWnd based components, their
function seems to go to sleep along with the main window. When they
reactivate they assume the position they would have had they never
gone to sleep to begin with, which leads me to believe that the
messages concerning the components are being sent, but not
being handled until the main program wakes up.

I'm certain that all of the elements of the splash screen are
independent of the main program, so I'm a bit blinded to the reason
that they would be stalled.

This is not an issue for any direct drawing functions that I do on the
main splash window (using CDC::Bitblts/AlphaBlands instead of having
CWnds with pretty pictures for backgrounds). Since both gfx and layer
window components are handled by the same message, it seems pretty
much the entirety of the problem lies with the calls to "SetWindowPos"
from the layered components themselves.

Is there something I am missing?

Well, there might be several things you are missing. Sleep freezes only
the thread it is executed in. The threads will run independently if
they are independent. But if you call any CWnd function from a thread
that did not create the CWnd then the calling thread stops and wait for
the owning thread to execute something: deadlock if the owning thread is
sleeping.

Don't sleep, and don't manipulate windows from a thread that did not
create them, and don't try to create child windows whose parent was
created in another thread. If your splash thread needs to do something
to a window created in the main thread use the PostMessage technique
shown here:

http://vcfaq.mvps.org/mfc/12.htm

--
Scott McPhillips [VC++ MVP]