Safari on Windows does not deliver WM_MOUSEWHEEL notifications to the HWND passed to NPP_SetWindow. I have verified this behavior with Safari 3.1, Safari 3.2, and yesterday's nightly build on Windows XP. Chrome and Firefox both deliver the notification.
If it would help, I can attach reduced testcase plugin code -- or at least, as reduced as NPAPI plugin code can reasonably get.
I am only able to find two references to NPP_SetWindow in Webkit Github mirror, one is in inline comments below:
While other is in Manual Tests file - NPN_Invoke/main.c
Since NPAPI plugins are not supported from Safari 14 onward and also not supported in WebkitGTK builds. Can we close this as "RESOLVED WONTFIX"?
This is Safari on Windows bug and if NPAPI plugins are supported on Windows build of Webkit, then please ignore my comment. Thanks!
NPAPI plugins have indeed aged like milk. Per Ahmad's suggestion, marking this one resolved by the sands of time.