Updating printers while application is running?

[Tobias Oelgarte]

I don't know if there is an common event available in the Java2D backend 
to detect added/removed printers directly. So far i could not see 
anything like that.

Every PrintService instance should implement the equals() [1] method to 
determine uniqueness. This could be used to compare/intersect the 
observable set of printers hold by javafx.print.Printer#getAllPrinters() 
against the array of PrintService instances exposed by 
PrintServiceLookup.getPrintServices(...). That way it should be possible 
to detect if a printer was removed or added. It could also be used to 
update the default printer property (on access and/or periodically).

[1] 
https://docs.oracle.com/en/java/javase/18/docs/api/java.desktop/javax/print/PrintService.html#equals(java.lang.Object)

On 07.06.22 21:44, Philip Race wrote:
> Ahem .. well .. I guess we (I) forgot to get back to that.
>
> Since the current implementation on Windows wraps the Java 2D printing 
> code
> and it registers with windows to be told about changes in printers 
> then the
> calls being made in the method with that comment would (well, should) 
> provide
> the updated printers ..
>
> The comment was (I think) referring to the need to know when there was 
> actually
> a change there to avoid perpetual re-creation.
>
> If the 2D side is working as expected I'll see if there's something I 
> can do along the lines
> of a quick check every time that the number of underlying printers is 
> the same and then if not it is worthwhile,
> coupled with a refresh every 2 minutes so it should never get too stale.
>
> -phil.
>
> On 6/7/22 11:39 AM, Tobias Oelgarte wrote:
>> Is there some way to update the ObservableSet of Printers once the 
>> Application is running? Calling Printer.getAllPrinters() always 
>> returns the same OberservableSet and it does not change - ever. [1]
>>
>> We have an JavaFx based application running under Windows 10/11 that 
>> is used to print on wireless printers, that are not always available. 
>> Having to restart the the application every time a printer goes away 
>> or comes available is a serious pain for the users.
>>
>> Is there any kind of workaround?
>>
>> I doubt it will be fixed in the near future, since this comment is 
>> from 6 years ago [2]:
>>
>>     // This is static. Eventually I want it to be dynamic, but first
>>     // it needs to be enhanced to only create new instances where
>>     // there really has been a change, which will be rare.
>>
>> [1] 
>> https://stackoverflow.com/questions/38470568/javafx-doesnt-detect-changes-of-available-printers
>>
>> [2] 
>> https://github.com/openjdk/jfx/blob/master/modules/javafx.graphics/src/main/java/com/sun/prism/j2d/PrismPrintPipeline.java#L99
>