Last modified: 2014-06-21 19:58:05 UTC
Right now we select all state-collapsed elements when the document is ready and hide them (without animation, but still, they are hidden *after* they are first shown, no matter how short that initial show is). The problem with that is that it is a exponentially slow operation (ON). By using CSS instead the initial state will be reflected immediately without any delay. Just like CSS "a { color: green; }" will make all anchor tags green (even anchor tags parsed after the CSS was parsed), likewise CSS like ".client-js .mw-collapsed { hidden }" will make them hidden without delay. On top of this, we can build further and also optimise the cost of animations. Instead of animating with javascript, lets let JavaScript only toggle classes and the CSS will take care of the state and (if CSS3 is supported) make the transition animated.
*** Bug 42535 has been marked as a duplicate of this bug. ***
Krinkle: As this has the 1.21.0 target milestone set and you assigned this to yourself, just a reminder that this would require a patch in the next weeks, as a 1.21.0 tarball is vaguely planned for May 2013.
Removing target milestone that was in the past. If you want this in a specific release, have a good reason AND you are willing to find resources to fix this bug, feel free to change it to something appropriate.