On Wednesday 11 September 2002 10:07 am, Andreas Raab wrote:
> Ned,
>
> > What about the WM_POWERBROADCAST message (at least for non-WinCE
> > apps)?
>
> You missed my point entirely or perhaps I didn't make it clear
> enough. Of course there are ways of getting notified (there always
> are) in the VM about a startup but what should the VM do?! It
> doesn't know enough about the resources associated (like, for
> example, what files are open and where the files come from) nor
> does it know about how to handle this situation in the context of
> some application or other. E.g., even assuming that we'd be
> enumerating the entire object memory to find all the file handles,
> do we actually know which ones to reopen?! Do we know how to handle
> failure situations?! Do we know if it's appropriate to reopen a
> network connection or not?! At the VM level, we just don't. And
> that's the problem. So the best I could eventually do is to pass
> some notification up to the Squeak level. But even then it's not
> always clear how to handle the situation. It would be much simpler
> if you could rely on the OS to handle these things for you if it
> pulls away the carpet under your feets ;-)

I agree that the OS shouldn't change the state of the system when the 
power comes back up, if it can manage not to. But Squeak _could_ be 
more power-aware, especially for PDAs.

We're in a position in the VM to actually remember sockets and file 
handles.

We can hear that the power's going down from the OS and refuse to 
power down if we have a network file share open that isn't cached 
locally.

We can hear that the power came back up and we need to repaint the 
window.

We can notify the OS that we're actually busy when we are doing 
something so it doesn't power us down.

We could close sockets and remote file handles on power-down. We're 
already detecting attempted operations on closed handles and raising 
exceptions. We could if we wanted, remember that we closed the files 
because of power-down.

As you point out, handling such errors is the concern of the 
application, but we could at least raise a recognizable exception to 
let the application know what happened: i.e. the difference between 
"tried to read from a file that was already intentionally closed 
(software error)" and "tried to read from a file that was closed on 
power down (not a software error)".

There are guidelines here for dealing with power management in Win2K:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnhdware/html/powermgt_tips.asp

-- 
Ned Konz
http://bike-nomad.com
GPG key ID: BEEA7EFE