Re: Locking Desktop and Threading Issue

Thanks for the advice, basically my forms cover the full desktop, they
are survey forms that the user takes an action against, HR related
stuff. I can get the forms to cover the full desktop in normal
processing, I have a class that does this ok, but if for example the
user locks the desktop and the application creates a form when the
user unlocks the desktop the form does not show on the full desktop
and the windows taskbar is shown, I realise this is probably normal
behaviour for windows, this is why I wanted to sleep the application,
so it can no process the form and then when it wakes up again the
application can create the normal form covering all the windows
desktop. So if I sleep the thread I can then wake it and process as
normal when the session event is unlock. So maybe I need to let it
process as normal and go back to my windows handler for the covering
of the desktop and check that piece,

Thanks
Eamonn

On 1 May, 18:41, "Peter Duniho" <NpOeStPe...@xxxxxxxxxxxxxxxx> wrote:
On Tue, 01 May 2007 09:35:44 -0700, Jenbo <eamonnjenni...@xxxxxxxxxxx>
wrote:

Hi, I have an application that displays forms on the users desktop,
what I am doing with it is having a SystemEvents
SessionSwitchEventHandler to capture the lock of the desktop, I would
like to kill the forms when this event is captured, that piece is
fine, but I would like to sleep the app until the
SessionSwitchReason.SessionUnlock happens then I can wake it again and
go the correct part of the code? Can I wake a sleeping thread, or
should I not sleep the thread at all, is there another way to get the
thread to sleep or hibernate and then wake u

It's not clear to me that there's really any need to do any of the things
you want to do. What are your forms doing that you can't just leave them
open when the desktop is locked? Windows will take care of hiding them
from the user and preventing user input, and when the desktop is unlocked
then they will still be there, ready to go. Windows is also smart enough
to not dedicate any attention to the user interface of the application
while it's essentially inactivated by the desktop being locked (not that
the UI component of an application is generally a significant load on the
computer in the first place).

That said, it is possible to explicitly get a thread to simply stop doing
anything. Under Windows, a thread cannot "sleep" or "hibernate" per se
(not in the sense that the computer can do those things), but you can
create a waitable event and call the WaitOne() method on that. The thread
that calls that method will stop and wait at that call until some other
thread sets the event, releasing the thread for further execution.

If you use a ManualResetEvent, and you insert a call to the event's
WaitOne() method at some appropriate spot (generally a point in some
code's processing loop that is executed often enough that latency for any
pausing of the thread will be low, but not so often that calling WaitOne()
causes a significant performance problem), then when you want the thread
to pause you reset the event and when you want the thread to continue to
set the event.

Of course, you still need at least one thread around to process the
SessionSwitchEvent and manage any other threads that are blocked. But I
suppose if you have a thread that is doing something particularly i/o or
CPU intensive and you want it to stop taking system resources when the
desktop is locked, you could build in this sort of pausing mechanism
without affecting the main GUI thread.

If the above doesn't help you, perhaps you could be more explicit about
why it is you believe you need to "put your application to sleep" when the
desktop is locked. This isn't something that normally needs to be done,
so you should probably be more clear about what abnormal situation exists
in your scenario that justifies or demands that sort of behavior.

Pete


.

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