[OpenJDK 2D-Dev] RFR: 8204391: Colors with alpha are painted incorrectly on Linux

[Jayathirth D V]

Hi Phil,

Thanks for fixing the regression introduced by https://bugs.openjdk.java.net/browse/JDK-8176795 .
I went through the changes present in http://cr.openjdk.java.net/~prr/8204931/ and it looks fine.
I have added detail review summary in the bug itself.

We can also ask Clemens to take a look at the change.

Regards,
Jay

-----Original Message-----
From: Phil Race 
Sent: Friday, July 27, 2018 1:12 AM
To: 2d-dev
Subject: [OpenJDK 2D-Dev] RFR: 8204391: Colors with alpha are painted incorrectly on Linux

Bug: https://bugs.openjdk.java.net/browse/JDK-8204931
Webrev: http://cr.openjdk.java.net/~prr/8204931/

There is a long evaluation in the bug report, so what I write here is just a summary.

This is a regression introduced by
https://bugs.openjdk.java.net/browse/JDK-8176795
and specific to the Xrender pipeline

The bug is that when using colors with alpha, the alpha is being ignored and the colour copied rather than blended, since we no longer pass the "pre-multiplied" 
flag as false.

The fix is to pre-multiply the colour when storing as a pixel even for an opaque xrender surface.

With this fix automated jtreg tests, and tck tests pass, as well as the manual TCK test that was failing.

Additionally the supplied regression test passes on all platforms.

-phil