Bug in handling buttons and other clickable controls in IE8 and higher

[mauritslamers]

When a user presses a button in IE8 (and probably also higher), IE will create three events: a mousedown, a mouseup and a click event. SproutCore seems to be dealing with this situation by only accepting the mousedown and mouseup events by catching the click event in this case (done in SC.RootResponder).

However, it turns out that there are situations in which only a click is generated. This situation is that a user using both IE and a screenreader presses a button. Chrome and Firefox automatically convert this to mousedown and mouseup, IE however does not. SproutCore still catches the click event, causing any clickable view to not be clickable.

The "offending" line is https://github.com/sproutcore/sproutcore/blob/master/frameworks/core_foundation/system/root_responder.js#L2189. It is obvious that it is intended to catch browser behavior which allows actions on a click event where the mouseDown and mouseUp events already have been handled.
From the code and my own logging I have understood that in these cases the click event will be generated last. However, the current solution will in this case catch all click events because the conditions will always be true, in the sense that a mouseup always will have been taken place before.

So the question becomes: is it possible (and if yes, how) to know whether an isolated click event takes place?