<AWT Dev> [9] Review request for JDK-8017472 [macosx] Transparency demo is not correctly dragged on the second monitor

[Alexander Zvegintsev]

Hello AWT team,

please review fix
http://cr.openjdk.java.net/~azvegint/jdk/9/8017472/00/
for
https://bugs.openjdk.java.net/browse/JDK-8017472

Another issue was closed as a duplicate of this one, but it has a better 
self-explaining title:
MouseEvent has wrong coordinates when using multiple monitors

 From mainScreen documentation[1]:
> The main screen is not necessarily the same screen that contains the 
> menu bar or has its origin at (0, 0).
> The main screen refers to the screen containing the window that is 
> currently receiving keyboard events.

absY should be calculated relative to a primary screen

According to documentation[2] primary screen can be obtained by call 
[[NSScreen screens] objectAtIndex:0]:
The screen at index 0 in the returned array corresponds to the primary 
screen of the user’s system.
[1]https://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSScreen_Class/Reference/Reference.html#//apple_ref/occ/clm/NSScreen/mainScreen
[2]https://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSScreen_Class/Reference/Reference.html#//apple_ref/occ/clm/NSScreen/screens

-- 
Thanks,

Alexander.