35276 - offsetWidth/Height not in sync with style.width/height

Status: VERIFIED FIXED

(Core :: DOM: CSS Object Model, defect, P3)

Description

[Joe Hewitt]

Apparently the offsetWidth and offsetHeight properties are not updated 
synchronously whenever .style.width and .style.height are modified.  This is a 
real problem because it essentially makes these properties meaningless.  

As a practical example, in a DHTML animation, if an element's size is 
constantly changing, and the script wants to rely on .offsetWidth 
and .offsetHeight to determine the current size, the obviously cannot do so.  
However, relying on the style properties is also not a good idea because you 
don't know if the element's size was set inline (and we don't have 
getComputedStyle() yet either, to find out the cascaded size).

Comment 1

[Joe Hewitt]

Attachment: see the bug in action

Comment 2

[Johnny Stenback (:jst)]

Joe, could you test if adding

  user_pref("layout.reflow.async.afterDocLoad", false);

to your prefs.js fixes this?

Comment 3

[Joe Hewitt]

Adding that line to prefs.js does in fact fix the bug.  Will this be a permanent
addition to the code?

Comment 4

[Johnny Stenback (:jst)]

No, it will not, and it's not even possible to do that any more (or adding that
line doesn't change anything any more). But it does confirm my theory tho so
thanks for testing. The problem is that modifying the dom tells gecko to reflow
the changed content but this is done asynchronously so if you ask for
style.width immediately after you change something you probably won't see the
changes. Now I just haveto figure out how to get arround this, we probably
need to add code that flushes all pending reflows before returning style
properties through the dom, I'll look into this...

Comment 5

[Johnny Stenback (:jst)]

I've got a fix for this, I'll land it as soon as I can (tomorrow probably)...

Comment 6

[Johnny Stenback (:jst)]

The fix is checked in, marking FIXED.

Comment 7

[Hixie (not reading bugmail)]

Taking QA Contact on all open or unverified DOM Style bugs...