src/java.desktop/windows/classes/sun/print/PrintServiceLookupProvider.java

*** 315,351 ****
              defaultPrintService = new Win32PrintService(defaultPrinter);
          }
          return defaultPrintService;
      }
  
      class PrinterChangeListener implements Runnable {
!         long chgObj;
          PrinterChangeListener() {
!             chgObj = notifyFirstPrinterChange(null);
          }
  
          @Override
          public void run() {
!             if (chgObj != -1) {
!                 while (true) {
!                     // wait for configuration to change
!                     if (notifyPrinterChange(chgObj) != 0) {
!                         try {
                              refreshServices();
!                         } catch (SecurityException se) {
!                             break;
!                         }
!                     } else {
!                         notifyClosePrinterChange(chgObj);
!                         break;
!                     }
                  }
              }
          }
      }
  
      private native String getDefaultPrinterName();
      private native String[] getAllPrinterNames();
!     private native long notifyFirstPrinterChange(String printer);
!     private native void notifyClosePrinterChange(long chgObj);
!     private native int notifyPrinterChange(long chgObj);
  }
--- 315,365 ----
              defaultPrintService = new Win32PrintService(defaultPrinter);
          }
          return defaultPrintService;
      }
  
+     /* Windows provides *PrinterChangeNotification* functions that provides 
+        information about printer status changes of the local printers 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.
+     */
      class PrinterChangeListener implements Runnable {
!         long prevRemotePrintersCount = 0;
! 
          PrinterChangeListener() {
!             prevRemotePrintersCount = GetRemotePrintersCount();
          }
  
          @Override
          public void run() {
!             while(true) {
!                 long currentRemotePrintersCount = GetRemotePrintersCount();
!                 if(prevRemotePrintersCount != currentRemotePrintersCount) {
! 
!                     // updated the printers data
!                     // printers list now contains both local and network printer data
                      refreshServices();
! 
!                     // store the current data for next comparison
!                     prevRemotePrintersCount = currentRemotePrintersCount;
                  }
              }
          }
      }
  
      private native String getDefaultPrinterName();
      private native String[] getAllPrinterNames();
!     private native long GetRemotePrintersCount();
  }