70328 - Absolute positioning of <div> using javascript is slow

Status: VERIFIED DUPLICATE of bug 69354

(Core :: DOM: Core & HTML, defect, P4)

Description

[Greg Breland]

This is really a testcase in search of a bug, but I hope it might be useful to
someone.  

I used very informal benchmarking to test the above URL in both Mozilla
2001022311 and IE5.5sp1.  Mozilla used 2X as much processor time moving the News
<div> around the screen.  All the time is spent in the mousemove() function
which is only 3 lines long.  I figured this would be a good test case someone
could profile against.  

I suspect the text hilighting code, but it could be the JS engine also.  Only
way to know is to profile it.  I did remove the text from the <div> with the
mousedown event.  This did reduce processor usage by 20% as there was no text to
hilight.  However, I think that the browser is still checking to see if text
needs to be hilighted and therfore slowing things down.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Attachment: The testcase in question

Comment 2

[Phil Schwartau]

This is a really interesting testcase! Here is the function mousemove()
that Greg pointed out above: 
 

function mousemove(evt)
{
 var myEvent = evt;
 if (document.all) myEvent = event;

 if(!(varmousedown == 0))
 {
  document.getElementById("counter").style.left = myEvent.clientX-varmousedown;
  document.getElementById("counter").style.top = myEvent.clientY-10;
 }
}



I'm going to presume this is a DOM issue, and reassign. I don't have the
necessary profiling application to know for sure; if it is actually JS Engine, 
please reassign back - thanks 

Comment 3

[Johnny Stenback (:jst)]

The problem described in bug 64516 also shows up on this page but there might be
more to this one than there is to the other one, I doubt it's a DOM problem tho...

Comment 4

[Greg Breland]

Bug 69354 is probably a dupe of this bug.

Comment 5

[Johnny Stenback (:jst)]

Since this one is newer than bug 69354 I'm marking this aa dup of that bug.

*** This bug has been marked as a duplicate of 69354 ***

Comment 6

[Fabian Guisset]

VERIFIED dup