<Swing Dev>  JDK-8153732: Windows remote printer changes do not reflect in lookupPrintServices()
shashidhara.veerabhadraiah at oracle.com
Wed Jun 20 10:12:03 UTC 2018
Hi All, Please review this code changes for the below enhancement.
Details of the changes: Windows provides *PrinterChangeNotification* functions that provides information about printer status changes of the local printers(subset) but not network printers.
Alternatively, Windows provides a way thro' which one can get the network printer status changes by using WMI, RegistryKeyChange combination, which is a slightly complex mechanism.
The Windows WMI offers an async and sync method to read thro' registry via the WQL query. The async method is considered dangerous as it leaves open a channel until we close it. But the async method has the advantage of being notified of a change in registry by calling callback without polling for it. The sync method uses the polling mechanism to notify.
RegistryValueChange cannot be used in combination with WMI to get registry value change notification because of an error that may be generated because the scope of the query would be too big to handle(at times).
Hence an alternative mechanism is choosen via the EnumPrinters by polling for the count of printer status changes(add\remove) and based on it update the printers list(both local and remote printers - superset).
Thanks and regards,
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