NEW235116
Summing up all movementX of mousemove events does not give the total difference in position 
https://bugs.webkit.org/show_bug.cgi?id=235116
Summary Summing up all movementX of mousemove events does not give the total differen...
Guillaume
Reported 2022-01-12 08:56:41 PST
The specification of the MouseEvent.movementX/Y properties says that > All motion data must be delivered via mousemove events such that between any two mouse events earlierEvent and currentEvent the value of currentEvent.screenX-earlierEvent.screenX is equivalent to the sum of all movementX movementY/code> events after earlierEvent, with the exception of when screenX can not be updated because the pointer is clipped by the user agent screen boundaries. (see https://w3c.github.io/pointerlock/#dom-mouseevent-movementx) It works perfectly fine in Chrome but does not seem to work as expected in Safari, as soon as I move the mouse I get differences of several hundreds of pixels. See the following CodePen: https://codepen.io/Latcarf/pen/YzrRvZE Tested with Safari Version 15.1 (15612.2.9.1.30, 15612), on MacOS Catalina version 10.15.7 (19H1615).
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Radar WebKit Bug Importer
Comment 1 2022-01-19 08:57:15 PST
<rdar://problem/87773443>
Wenson Hsieh
Comment 2 2022-01-21 17:46:58 PST
`WebPageProxy::handleMouseEvent` drops unhandled platform mousemove events on macOS if the mouse event queue is too backed up… Maybe that is what's causing this behavior?
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