Hi all,

as I am currently working on FXCanvas, there is one aspect I would like to 
discuss, which is closely related to JDK-8161282 
<https://bugs.openjdk.java.net/browse/JDK-8161282> (FXCanvas does not forward 
horizontal mouse scroll events to the embedded scene) and JDK-8143596 
<https://bugs.openjdk.java.net/browse/JDK-8143596> (FXCanvas does not forward 
touch gestures to embedded scene), namely handling of synthesized scroll 
events. That is, SWT synthesizes mouse wheel scroll events from PAN gesture 
events, and these are forwarded to the embedded scene (the patch I provided for 
JDK-8161282 does not change this behavior, it simply ensures horizontal and 
vertical mouse wheel events are processed equally) while not being marked as 
synthesized (unlike MouseEvent, ScrollEvent does not provide a ‚synthesized‘ 
flag). JavaFX natively seems to do likewise with SWIPE events, which seem to 
yield synthesized scroll events as well. 

Wouldn’t it be appropriate to introduce a synthesized flag and mark such kind 
of events as being synthesized? Within the Eclipse GEF’s FXCanvasEx we have 
sorted out scroll events synthesized form PAN events completely (and any client 
code may do likewise without accessing internal API, so this is no JIGSAW 
related issue), but I think it in general be nice if client code could properly 
decide, whether it wants to deal with these events or rather handle the native 
gesture events instead (as soon as JDK-8143596 is resolved this would even be 
possible in an SWT-integrated scenario).

I would raise an issue via webbug for this, if my thoughts are shared.

Regards,
Alexander


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