Bug 276659 – [GTK][X11] Pointer lock drifts if started while moving

• Component: WebKitGTK
• Status: RESOLVED FIXED

[Roope Salmi]

Created attachment 471892 [details]
Example HTML demonstrating the issue

Ubuntu 22.04.4
WebKitGTK local build of main https://commits.webkit.org/280684@main

HTML (attached):

<div id="box" style="background:red; width:50px; height:50px; position:fixed;"></div>
<script>
	let x = window.innerWidth / 2;
	let y = window.innerHeight / 2;
	function update() {
		document.getElementById("box").style.left = x;
		document.getElementById("box").style.top = y;
	}
	update();
	document.addEventListener("mousemove", (e) => {
		x += e.movementX;
		y += e.movementY;
		update();
	});
	document.addEventListener("mousedown", (e) => {
		document.body.requestPointerLock();
		x = e.clientX;
		y = e.clientY;
		update();
	});
</script>

On mousedown, the box moves to the mouse and follows it.

Move the mouse and simultaneously press LMB. Now move the mouse in a circular pattern. The box will move indefinitely in one direction, while it should stay at around the same place.

Follow-up from https://bugs.webkit.org/show_bug.cgi?id=273876
See https://github.com/WebKit/WebKit/pull/30437#issuecomment-2228773994

I am planning to write a second PR to fix this.

[Roope Salmi]

Pull request: https://github.com/WebKit/WebKit/pull/30908

[EWS]

Committed 281232@main (c99908cf384c): <https://commits.webkit.org/281232@main>

Reviewed commits have been landed. Closing PR #30908 and removing active labels.