[OpenJDK 2D-Dev] RFR: 8263984: Invalidate printServices when there are no printers

[Prasanta Sadhukhan]

On Wed, 24 Mar 2021 09:25:56 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> src/java.desktop/windows/classes/sun/print/PrintServiceLookupProvider.java line 120:
>> 
>>> 118:             // don't get the default.
>>> 119:             invalidateServices();
>>> 120:             printServices = new PrintService[0];
>> 
>> I am not sure this call to invalidateServices() is needed as we are creating a new `printServices` object of 0 length so making the old printServices invalid is redundant as it is same global variable.
>
> That's exactly the problem I am addressing.
> 
> In the regular case, the existing services left in `printServices` are invalidated before `newServices` is assigned to it. Yet no existing services are invalidated if all the printers were removed from the system.
> 
> Why is it needed to invalidate deleted services if the list of printers is updated and if at least one printer is left in the system? Why is it not needed to invalidate deleted services if all the printers are removed from the system?

Since this is windows specific code, I am not sure if system will not have any printers. I guess by default, Microsoft XPS Document Writer, Microsoft Print-to-PDF, Fax are present in printers list. That is the reason we do not have getPrintService() return 0 printer although there may not be any real printer present in windows system...reason for some failure in jtreg test which caused us to use `@key printer `tag in those tests to make real printers are configured.

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PR: https://git.openjdk.java.net/jdk/pull/3151