Safari - updating a link's title via XMLHTTPRequest on mouse hover?

I'm doing some Mac development in a WebView. I want to expand URLs that have been shortened by a url shortener, and display that expanded URL to the user. So, given a link whose src attribute is set to http://is.gd/xizMsr, when the user hovers over the link I want the title tooltip to display http://google.com

My link tag looks like this:

<a href="http://is.gd/xizMsr" onMouseOver="myFunction(this);">Here's a shortened link to google</a>

And here's the relevant javascript, which will use XMLHttpRequest to fetch the expanded URL and then update the title

var myRequest;
var mousedOverElement;
var isLoading = false;

function myFunction(anObject) {
  if (isLoading == false) {

    isLoading = true;
    mousedOverElement = anObject;
    var link = anObject.getAttribute('href');
    var encodedURL = encodeURI(link);
    var url = 'http://is.gd/forward.php?format=simple&shorturl=' + encodedURL;

    myRequest = new XMLHttpRequest();
    myRequest.open("GET", url);
    myRequest.onreadystatechange = onStateChange;
    myRequest.send();
  }
}

function onStateChange()  {
    if (myRequest.readyState==4) { 
        if (myRequest.status==200) {   
            mousedOverElement.setAttribute('title',myRequest.responseText);
        }

        isLoading = false;
    }
}

The problem is, when I hover over the link, and then stop moving the cursor, the title attribute is set properly, but the tooltip is not shown. I have to move the mouse again to make the tooltip show up. I don't necessarily have to move the cursor off of the link and then back over it, but simply moving a few pixels while remaining hovered over the link will do the trick.

I know that the title is being set properly from a combination of using the Web Inspector and the Ja开发者_JAVA技巧vascript debugger in Safari. In fact, pretty much as soon as I hover over the link, I see the Web Inspector's view of the DOM in the "elements" tab update with the new title. But, if I take my hand off of the mouse, the tooltip never shows.

My assumption here is that WebKit only shows a tooltip when the user is moving the mouse. Is there a way to sort of "wake up" webkit, even if the cursor is not moving? Or am I better off implementing this with some of my own DHTML-ish magic instead of relying on the title attribute?

What about an element (move it over the anchor) or a wrapper (positive z-index) with a transparent background which will (onmouseover):

1. first add the anchor's title (you will have to modify your function)
2. and then change its (negative for the covering element) z-index (effectively putting the anchor in the foreground)

This way the title will be readily available. If necessary you can add a setTimeout() between step 1 and 2.

Or you could simply use setAttributeNode to modify the title attribute value.

You said

"The problem is, when I hover over the link, and then stop moving the cursor, the title attribute is set properly, but the tooltip is not shown."

Its likely that because the title did not exist when you started the mouse hover, it could not display any tooltip (there was nothing to display). So no tooltip will appear. When you move the mouse again, this time it does have a title attribute, so it can display a tooltip. Theres not much you can do about that, its just how the browser works.

Instead your could try using a jQuery tooltip: http://www.reynoldsftw.com/2009/03/10-excellent-tooltip-plugins-with-jquery/

With jQuery you should be able control it so that a tooltip appears as soon as the title is set.