Re: Delegate.BeginInvoke and EndInvoke.

Maybe you're calling SystemParametersInfo during a message that does block
the message pump?  I'd have to check, but I could see a windows message
pump not processing any messages while the application was processing
WM_CLOSE, for example.


On Thu, 17 Jan 2008 08:44:06 -0700, Bhatnagar, Amit
<[email protected]> wrote:

>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.
>
>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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