Firefox 在文本上拖动时触发 dragleave

I'm attempting to track a dragenter/leave for the entire screen, which is so far working fine in Chrome/Safari, courtesy of the draghover plugin from https://stackoverflow.com/a/10310815/698289 as in:

$.fn.draghover = function(options) {
    return this.each(function() {

        var collection = $(),
            self = $(this);

        self.on('dragenter', function(e) {
            if (collection.size() === 0) {
                self.trigger('draghoverstart');
            }
            collection = collection.add(e.target);
        });

        self.on('dragleave drop', function(e) {
            // timeout is needed because Firefox 3.6 fires the dragleave event on
            // the previous element before firing dragenter on the next one
            setTimeout( function() {
                collection = collection.not(e.target);
                if (collection.size() === 0) {
                    self.trigger('draghoverend');
                }
            }, 1);
        });
    });
};

function setText(text) {
    $('p.target').text(text);
}

$(document).ready(function() {
    $(window).draghover().on({
        'draghoverstart': function() {
            setText('enter');
        },
        'draghoverend': function() {
            setText('leave');
        }
    });
});

但是，当我拖动文本项时，Firefox 仍然给我带来问题，这里有一个小提琴来演示:http://jsfiddle.net/tusRy/6/

try {
    if(event.relatedTarget.nodeType == 3) return;
} catch(err) {}
if(event.target === event.relatedTarget) return;