Bug 99682 – onmouseover doesn't get triggered consistently by DOM manipulation

• Component: DOM
• Status: UNCONFIRMED

In an HTML page when two elements overlap, and the top element is hidden by setting the display to "none", the bottom element's onmouseover event doesn't always get sent.

In particular, in the attached test page, I have it set up so the top element is hidden when I click on it. In the first case the CSS change happens immediately during the click event handler and the bottom element does get the mouse over event. In the second case, I set a timer to set the CSS display to "none" later, and the onmouseover event didn't get sent. Seems like this depends on whether the DOM manipulation happens during a mouse event handler.

Two additional notes:
1) The :hover state gets triggered immediately in both cases, which seems weird to me. Basically :hover is triggered, but onmouseover isn't.
2) This seems to work correctly in Firefox/Gecko.

Created attachment 169346 [details]
Test page. Click on the top element and don't move the mouse and observe the log on the right. Ideally you should see a mouse over event.

[Lucas Forschler]

Mass move bugs into the DOM component.