702579 - Display lag of background image after tab inactivity

Status: RESOLVED WONTFIX

(Core :: Graphics: ImageLib, defect)

Description

[Loic]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20100101 Firefox/8.0
Build ID: 20111104165243

Steps to reproduce:

1/ Open a tab and go to http://eu.battle.net/wow/fr/ (WoW website)
2/ Open a 2nd tab and go to it.
3/ Wait for 20 or 30 sec (maybe less).
4/ Go back to the 1st tab.


Actual results:

The background image of the website (URL: http://eu.battle.net/wow/static/images/layout/body-bg-baked.jpg ) is not displayed immediately when the tab is selected, there is a display lag.


Expected results:

I have observed this issue in FF8 (and higher), not FF7. I know FF8 did some improvements about image decoding during tab inactivity to reduce memory consumption, so maybe it's the normal behaviour now.

Comment 1

[:aceman]

Yes, as you say, this was intentional
Try going to about:config and set image.mem.min_discard_timeout_ms to some higher value. It is in milliseconds so the default is 10000 (10 seconds). After that Firefox will remove images from memory fro inactive tabs. use a higher value if you wish to preserve them longer (at the cost of memory usage).
See the linked bugs.

Comment 2

[Justin Lebar (not reading bugmail)]

> so maybe it's the normal behaviour now.

It is normal behavior, and you're spot on -- it's a memory-usage tradeoff.  There are some things we can do to re-decode the images faster, so there's less delay.  Right now, for example, we immediately decode all the images on a tab when you switch to the tab.  But really, we should only decode the images which are in view.

See bug 683284 for a bunch of things we'd like to do to improve images.

Comment 3

[Loic]

Okay, thanks both of you for your advices, I will follow these bugs and play with image.mem.min_discard_timeout_ms in about:config.