Ticket #514 (closed defect: cantfix)
Bad performance in virtualBuffers for web pages with extremely busy javascript
| Reported by: | Agent Golder | Owned by: | |
|---|---|---|---|
| Priority: | major | Milestone: | |
| Component: | Browse mode | Version: | |
| Keywords: | virtual buffers freaz | Cc: | kmix@otenet.gr, blindangel@freemail.gr |
| Operating system: | Windows 7 | Blocked by: | |
| Blocking: |
Description (last modified by mdcurran) (diff)
Cases like www.greek-chater.com.
After it has completely loaded it doesn't respond at all untill I switch
to another application!
Sometimes says things such as "Icon" and "Unknown object", new to me!
And I setted the system to Windows 7 because I'M not sure about it in
others...
Again, I'M using the latest stable 2009.1 which isn't in the list.
Any idea?
Change History
comment:3 Changed 2 years ago by mdcurran
- Description modified (diff)
- Summary changed from NVDA freazes in "large pages"!!!! Please help! to Bad performance in virtualBuffers for web pages with extremely busy javascript
Woops, changed wrong field. Fixing up
comment:5 in reply to: ↑ 1 Changed 2 years ago by Steve Buell
Replying to mdcurran:
The content which is continually updating is a visual effect of snowflakes (the 510 line "snowstorm.js") which reacts to the position of the mouse pointer. Very "1999" web design. This would probably be your culprit.
There is also a lot more JS for user agent data collection, twitter posting, image resizing and some Yahoo user interface objects.
This does not affect performance when tabbing or mousing without a screen reader running.
The fault here lies with the site designer, not the assistive technology.
NVDA is developed by 
There does seem to be quite a lot of content updates on this page after the page loads.
I'm not sure, but it seems to be quite a significant chunk of the page which keeps updating about once every second. (it may be the entire document), as NVDA is taking about 0.2 of a second to complete the update.
However, its not NVDA updating its virtualBuffer which is slowing things down, as NVDA's performence with Firefox on this page is really bad even between updates. I guess this means that there is some very busy javascript on this page, either that or firefox is downloading a lot of content via xhttp or what ever.
Note that things like nvda+f12 work fine, alt tabbing works fine, which means that its definitly Firefox which is slow.
Specifically, Firefox is taking a very long time to set focus to the object arrowed to with the virtualBuffer.
I'd be interested to know if a sighted user notices performance loss when tabbing or mousing around this page (with out a screen reader running).