[9] Review request for 8166414: Scene returns incorrect coordinates

[Semyon Sadetsky]

Hello Kevin & David,

Please review the fix for jfx9:

bug: https://bugs.openjdk.java.net/browse/JDK-8166414

webrev: http://cr.openjdk.java.net/~ssadetsky/8166414/webrev.00/

According to GTK iib documentation on X11 WMs the 
gtk_window_get_position() function doesn't return the exact window 
position coordinates but a guessed position where WM should place the 
decorated window by taking into account gravity attribute and extents. 
There are situations when algorithm used for guessing the window 
position doesn't produce good result. This may depend on the platform WM 
implementation.

As a fix I suggest to use window extent information which is collected 
on frame extent property notification. To get the correct position X and 
Y event coordinates should be decreased by top and left extent values 
correspondingly.

--Semyon