[OpenJDK 2D-Dev] Fix for JDK-8139192 : Custom ImageFilters return blank images in Java 8(.45) while working in 7

[Jim Graham]

How about option 3 -

NPE before imageComplete sends an ERROR as it does now.

NPE during imageComplete is ignored, both for backwards compatibility 
and because it is more of a "hint" than an operation that requires 
action from the consumer.

			...jim

On 5/25/2016 1:31 AM, Ajit Ghaisas wrote:
> Hi
>
>
>
> Bug :
>
> https://bugs.openjdk.java.net/browse/JDK-8139192
>
> Custom ImageFilters return blank images in Java 8(.45) while working in 7
>
>
>
>
>
> Root cause :
>
> private method produce() in OffScreenImageSource.java consumes a
> NullPointerException that originates from a custom ImageConsumer (a 3^rd
> party image library class - com.jhlabs.image.WaterFilter)
>
>
>
>
>
> Analysis:
>
> 1. How the behavior changed between JDK7 and JK8 :
>
> A call to imageComplete(ImageConsumer.SINGLEFRAMEDONE) was added in
> addition to imageComplete(ImageConsumer. STATICIMAGEDONE)  as a fix for
> JDK-7143612.
>
>
>
> 2. What debugging revealed:
>
> A NullPointerException is being thrown from the library during the call
> to imageComplete(ImageConsumer.STATICIMAGEDONE)
>
>
>
> 3. It looks like the fix of JDK-7143612 is valid and successive calls to
> imageComplete() are allowed.
>
>
>
> 4. The 3rd party library behavior appears incorrect (if it can not
> handle subsequent calls to imageComplete(), it should de-register itself).
>
> The 3rd-party library code should be fixed.
>
>
>
>
>
>
>
> Possible modifications in JDK  :
>
>
>
> Currently, OffScreenImageSource::produce() consumes the
> NullPointerException - this is incorrect and results in silent failure
> of this particular image filter.
>
> We need to let the image filter library know that exception has occurred
> in its code and not in JDK. We have two options -
>
>
>
> Option 1 : Rethrow the NullPointerException   --- It is the clearest way
> to let 3^rd party library know that their code is erroneous with latest
> JDK. This will change the 3^rd party image filter behavior that
> generates blank image.
>
> Option 2 : Add a stack trace where the exception is being consumed ---
> Adding stack trace provides more information regarding failure of 3^rd
> party image filter with retaining the current behavior that generates
> blank image.
>
>
>
> I have implemented both the options:
>
> Option 1: http://cr.openjdk.java.net/~aghaisas/8139192/webrev.00/
>
> Option 2:  http://cr.openjdk.java.net/~aghaisas/8139192/webrev.01/
>
>
>
> Request you to review both the webrevs and provide your preference.
>
> I will add a test to the selected webrev.
>
>
>
> Regards,
>
> Ajit
>
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