11069 - alert() crashes eventhandler

Status: VERIFIED FIXED

(Core :: DOM: UI Events & Focus Handling, defect, P3)

Description

[csom]

[Type]: Javascript bug?
[Occurance]: modal windows and eventhandling
[Test]: OS=win NT4(hu) BROWSER=NN4(hu)/IE4(en)

Abstract
--------
The alert() function (generally modal windows) breaks the process flow (based
on the eventhandling model) in some cases

Example
-------
<A HREF="http://bugzilla.mozilla.org" >click</A>
<SCRIPT>
document.links[0].onclick = newLoc;
function newLoc(){
 location.href="newpage.html"
 alert("bug?")
 return true
}
</SCRIPT>

In the above example we catch the click event by setting:
   document.links[0].onclick = newLoc;

Because the eventhandler has a 'return true' statement after it terminated
the default action of the 'a href' tag must be executed, ie. it must jump to
netscape.com. That's what the event model says, however real life says
something else:

- if the user is quick enough to click the OK button and/or the new.html page
is far enough to be downloaded slowly then yep the browser jumps to
bugzilla.mozilla.org, however

- if the user is slow to click and/or the newpage.html is close enough to be
downloaded then sure it gets downloaded which means that it clears the previous
document. So the eventhandler cannot terminate, the link cannot be folowed due
to the fact that the calling document is cleared.

Ps.: the same happens if you replace alert() with confirm() or prompt() method.
Generally (I guees) modal windows may cause bugs like this however I've just
tested these 3 samples

Comment 1

[joki (gone)]

I'm not sure what the appropriate behavior is here.  In 4.x, my browser seems to
always load the location.href link but I don't know if that's timing or what.
The location.href obviously doesn't immediately replace the content, else the
alert would not fire.  But the link, I don't *think* should get executed based
on the execution of the location.href line.  Ideas?  CC'ing brendan and vidur

Comment 2

[Jan Carpenter]

This doesn't crash for me on any platform.
1999061209
Marking fixed and verified

Comment 3

[Jan Carpenter]

checked on WinNT, Win98, Linux, Mac