Help needed to understand point n print
Gerald (Jerry) Carter
jerry at samba.org
Tue Aug 22 15:32:29 GMT 2006
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Martin Zielinski wrote:
> Hello Gurus!
> When using a printer that is served by a (samba)server and I replace a
> driver file on this server, this file will become updated on the client
> I've two questions about this:
> 1st: What makes the client recognize, that a file has been updated? I
> know, that the client compares all the files but what lets him do so?
> Time schedule or this magic "ChangeID" printer data value on the server?
ChangeID. That is the sequence number on a printer.
When the changeID is different that what the client has cached,
it attempts to refresh its cached printer object.
> 2nd: The update seems to happen randomly. But when I open
> the property sheet, it's a good bet, that the file
> will become updated instandly. Does any one know
> how this is done by the client? The replaced file is
> definitly in use (e.g. by the property sheet
> itself). And this should prevent copying the file
> to the driver directory.
There's a race condition in that the client is attempting
to update its cache and display the properties. Sometimes
you have to close the properties and reopen them to get
the correct (current) view.
> Background: (why this questions aren't off topic)
> I work on a generic way to make local printers behave
> like PnP network printers. The goal is to enable the features
> that the drivers perform by using the print processor
> without loosing central security and driver management.
> These features (e.g. Watermarks) are currently not usable
> with network printers on samba servers.
Yup. You need a local proxy printer. Although if you
just implement an EMF rendering engine that Samba could
call out to, you don't need any client mods. I think
an Linux x86 using WINE would even be sufficient.
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