[OpenJDK 2D-Dev] <Swing Dev> [10] Review Request 8187367: Numerous swing display problems with scaled displays on Windows

[Semyon Sadetsky]

Hello,

Please review fix for JDK10 (in Swing and Java2D):

bug: https://bugs.openjdk.java.net/browse/JDK-8187367

webrev: http://cr.openjdk.java.net/~ssadetsky/8187367/webrev.00/

Swing apps  may have artifacts on HiDPI screens with fractional scales. 
There are several issues which may cause various artifacts but the 
current fix only eliminates one type of artifacts the vertical and 
horizontal lines on painted surfaces (other issues are addressed by [1] 
and [2]). This issue was introduced after 8073320 and then incorrectly 
fixed in 8163193.

The root cause is the painter pattern is drawn on a wrongly sized and 
scaled image in case the image is an off-screen volatile image. The 
painter doesn't take into account the volatile image inner scale 
transformation which is not an identity in case of HiDPI , so the 
resulting image is drawn on of off-screen surface that in the scale 
times bigger than it is actually necessary. Since such images are cached 
this was waste of RAM. Also, the bounds sent to the painter class don't 
take into account the transformation rounding error the latter caused 
artifacts on the drawing edges.

--Semyon

[1] https://bugs.openjdk.java.net/browse/JDK-8187585

[2] https://bugs.openjdk.java.net/browse/JDK-8187586