Re: Delegate.BeginInvoke and EndInvoke.

Thanks Peter for looking into this.

Well what I don't get is that it never hangs during my app's
initialization (where we get the current NC metrics), nor does it hang
when I minimize the app (where I restore the NC metrics). The only call
that causes it to hang is during shutdown. I have tried moving this from
my MainWindow's FormClosing event out into a call just after
RunApplication() returns, but that also sometimes hangs (process still
lives, main window is gone.) Isn't that odd? Shouldn't the window be
destroyed by the time we return from RunApplication() and thus no
messages should cause a hang?

Either way, running the call on a async delegate at least lets my
application to close, and I am not too worried that the delegate may not
return and cause a thread from the pool to hang because the application
is closing anyhow.

Not the best way to do things, but it'll do for now.=20

Do you know if .NET 3.5 has a better way of doing things? Is there
finally a .NET API to access these system settings?

-----Original Message-----
From: Discussion forum for developers using Windows Forms to build apps
and controls [mailto:[email protected]] On Behalf Of
Peter Ritchie
Sent: Wednesday, January 16, 2008 7:19 PM
To: [email protected]
Subject: Re: [DOTNET-WINFORMS] Delegate.BeginInvoke and EndInvoke.

The documentation for SystemParametersInfo details sending the cbSize
value for SPI_{G|S}ETCLIENTMETRICS; but I tried with 0 and it seems to
work too (the same value is in NONCLIENTMETRICS, so it doesn't *need*
it).

Okay, a little bit of testing shows that SystemParametersInfo (at least
with SPI_SETCLIENTMETRICS) is blocking, but it doesn't block the GUI
thread and it continues to pump messages.  In my test, while blocked on
the SystemParametersInfo(SPI_SETCLIENTMETRICS) the thread received the
following messages:
WM_WINDOWPOSCHANGING
WM_GETMINMAXINFO
WM_NCCALCSIZE
WM_WINDOPOSCHANGED

You can certainly get in a situation--since a function call is blocked
and messages can come in on the same thread while that's blocked--where
you can cause a hang.

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