On Mon, 29 Jul 2024 09:56:17 GMT, Prasanta Sadhukhan <psadhuk...@openjdk.org>
wrote:
>> src/java.desktop/macosx/classes/sun/lwawt/macosx/CPrinterJob.java line 756:
>>
>>> 754: boolean cancelled = (performingPrinting && userCancelled);
>>> 755: if (cancelled) {
>>> 756: cancelDoc();
>>
>> The comments about deadlock refer to isCancelled() but is that not also why
>> there was an invokeLater() ?
>> It is not at all clear to me. Perhaps you can explain how the deadlock would
>> occur and why it is not a problem for calling cancelDoc() ?
>
> This comment was there from initial macosx port. Since
> RasterPrinterJob.`isCancelled` relies on `synchronized` block and since this
> `cancelCheck` method was called from native, it might have been suspected
> that it might block the native AppKit thread, so `invokeLater` was added.
> But the problem was `LWCToolkit.invokeLater` is called with `null` argument,
> which was not a problem in initial macosx port but
> [JDK-8042087](https://bugs.openjdk.org/browse/JDK-8042087) got it modified in
> jdk9 to throw an exception if component argument is null, which is the case
> in `CPrinterJob.m#cancelCheck`
>
>> LWCToolkit.inokeAndWait is called on the Appkit thread, but if the
>> component argument is null it uses EventQueue.invokeLater which would fail
>> with an NPE in plugin mode. The method should be updated to throw an
>> exception in case the provided component is null.
>
> Coming to your question, I guess if there is a deadlock, calling `cancelDoc`
> directly will also face the same issue as it also relies on same
> `synchronized(this)` block but I could not find any deadlock issue with the
> printing for which this `invokeLater` safeguard was added...
>
> So, Is the above comment " fail with an NPE in plugin mode" still applicable
> i.e do we still support plugin mode?
> If not, we can restore invokeLater call in this code and use
> `Toolkit.getToolkit` if the component is null as it was[ previously to
> JDK-8042087
> ](https://github.com/openjdk/jdk/commit/bb2698cfa6f2bdc92c197f17a7d2f90003db05fa)
I dont see any deadlock in my testing so I am using `isCancelled` .
How do you normally "cancel" ongoing printing in macosx? I tried clicking on
"x" in "Print Centre" when the specific print job is shown in the printer
spooler and I dont see any deadlock for long printing tests like PrintAllFonts
etc..
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20027#discussion_r1696516561
