Task switching and Firefox

Buried deep in the main windows event handling of Firefox code, there’s a little bit of hackery that does something kind of funny when you minimize Firefox to the tray. The code was originally designed cut down on the working memory set of the Fx process when the main application window was minimized. Unfortunately there are some rare side effects from this code that cause interference in task switching with certain 3rd party apps. If you’ve ever run into a problem with Fx where it gets locked on the task tray and can’t be restored with an alt-tab, you’ve run into the problem.

Windows does a far better job today of managing the working set for minimized applications, making this code largely obsolete. But the code is still around for those that feel they need it. (A long time ago, I think when IE 7.0 came out, some bloggers criticized Fx for the minimized working set “problem”.)

Systems with ample memory really don’t need this hackery at all, so it can be safely disabled. Open up config (about:config) and add a new pref:

config.trim_on_minimize = false

This will disable Fx’s custom minimize code and let windows do it’s “normal thing” when Fx is minimized to the tray.

[Update – we disabled this by default in 6.0 for Vista and up.]