Bug 64047 – Page flashes when dragging a div on google.ro

• Component: HTML Editing
• Status: NEW

What steps will reproduce the problem?
1. Goto http://www.google.ro;
2. Click on the keyboard icon inside the search box, wait for the keyboard to be shown. 
3. Mouse down on the title of the keyboard;
4. Starting dragging the keyboard;
5. The page started to flash intensily.

What is the expected result?
The page shouldn't flash.

What happens instead?
The page flashed.

Please provide any additional information below. Attach a screenshot if
possible.

UserAgentString: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_7) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.100 Safari/534.30

Created attachment 99911 [details]
This is the video recording how to reproduce the bug.

[Alexey Proskuryakov]

I also see this with WebKit nightly r90503.

Looks like a selection temporarily appears.

[Kulanthaivel Palanichamy]

(In reply to comment #2)
> I also see this with WebKit nightly r90503.
> Looks like a selection temporarily appears.

The same issue is reproducible in Opera as well. But surprisingly Firefox and IE handle this scenario well.
Basically, when mousepress event is sent to the virtual keyboard's event handler, it suppose to set preventDefault on that event to make sure that default action is not handled on that event.

In EventHandler::handleMousePressEvent(const PlatformMouseEvent& mouseEvent) { 
...
    bool swallowEvent = dispatchMouseEvent(eventNames().mousedownEvent, targetNode(mev), true, m_clickCount, mouseEvent, true);
    m_capturesDragging = !swallowEvent;
...
}
- Here m_capturesDragging is set to true incase of cancelled events to prevent selection on subsequent mousemove events.

I'm not sure whether we need a specific workaround where selection should not get triggered when the corresponding events are handled by drag target's JS event handlers.