Page Zoom is relatively slow on larger pages, especially comments systems such as Disqus




7 years ago
4 years ago


(Reporter: DB Cooper, Unassigned)


Firefox Tracking Flags

(Not tracked)





7 years ago
User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.2a1pre) Gecko/20110328 Firefox/4.2a1pre
Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.2a1pre) Gecko/20110328 Firefox/4.2a1pre (Built from

On a large page, particularly one with a lot of blog comments, firefox is quite slow when resizing the page. Particularly when compared to Opera 11.

The test was performed on an Intel E8500 CPU/ATI HD4650 GPU based machine with all HW acceleration on (Win 7 64 bit, 32bit FF nightly, AMD Catalyst 11.2).

IE9 is generally faster as well, but "compatibility view" problems can complicate testing.

Reproducible: Always

Steps to Reproduce:
1. Open URL and wait to load.
2. Use Ctrl++ and Ctrl+- to resize beyond default
3. Use Ctrl+0 to return to default zoom
Actual Results:  
Considerable lag before page is resized.

Expected Results:  
Near instant resizing, as with Opera 11 and sometimes (see above) with IE9
I see about identical behavior with Opera 11 and current trunk, on Mac.

Comment 2

7 years ago
I see a noticeable difference on this page too (make sure you wait for the zoom to complete each step):

You will need to make sure that all comments are loaded and visible though. (need to use threshold dial, and hit the "get x more comments" button about 8 times.
And also make sure you're not using the old, working, commenting UI.

I do see us being slightly slower than Opera there.  A profile shows that this has nothing to do with graphics; 12% is invalidating, maybe 10% is reflow, and 62% is the style reresolution, about half of this under SelectorMatchesTree.  There's ongoing work to make this faster, but in the end as long as zoom involves a full restyle it'll take time...
Component: Graphics → Layout
QA Contact: thebes → layout

Comment 4

7 years ago
Thanks Boris. Perhaps this is less visible on faster CPUs? (I performed this on an E8500).
Could be; I'm testing on an i7-620M...

Comment 6

7 years ago
E6750 CPU here.  I see a lag that I'm guessing is 250-500ms on the first URL given.  

Never thought 'lag' like that was too big of a deal since UI doesn't freeze, just thought I'd provide information for the bug.

Comment 7

6 years ago
The avclub page linked in the original bug report has changed to a disqus comment system. 

When resizing the page (try zooming twice then using Ctrl+0 to return to default) FF nightly (win32, today's moz-central build, D2D/D3D10, Win 7 64bit) is significantly slower than IE9, Chrome (stable), and Opera Next. 

FF has improved but still lags all competitors.


6 years ago
Summary: Page Zoom is relatively slow on larger pages → Page Zoom is relatively slow on larger pages, especially comments systems such as Disqus
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