Partial menu disappearance (cut) when "Page compression" is on

Thanks for taking the time to report this issue.

However, marking as duplicate of #601918: Default css overrides toolbar css.

bump! my admin menu disappears when 'page compression' is turned on.. clearing cache fixes it for one single page view, then usually it goes away. please re-open this issue, thanks!

edit: I need to do more troubleshooting. Here's what I've found soo far:

-once it disappears, 'performace->clear cache data' will bring it back until the page it refreshed.
-after a 'clear cache data', you can navigate to any page and will see the menu until any page is refreshed.
-once it disappears, it will not show for any other pages until performance clear cache data.
-this problem is not dependent on theme
-no other performance options seem to make any difference on this problem

This issue should be fixed in the latest development snapshot.

I'm now running the latest Feb20th 6.x dev and I don't see any change. Are there any notes you could share on what the problem was/is? Thanks!

edit: the difference I've found in the new dev version is that navigating away from the performance page will kill it, whereas before you could navigate away as long as you didn't click 'refresh' on any of those pages. Also, I've found that once it breaks in one session, it will break it for all sessions.

I confirm all above.
With page compression turned on about half of the menu suddenly disappears and only cache cleaning or turning page compression helps.

I'm on the latest git version:

commit 6ecf9c6ea7bee6378e04cda38fec47785c258a4f
Author: sun <sun@unleashedmind.com>
Date:   Thu May 17 23:14:46 2012 +0200

I wonder why original topic was saying about "JS compression". The bug triggers when Page compression is turned on actually and it doesn't depend on Toolbar or whatever style.

Admin menu was only partially rendering on my site. It would show the icon menu, the "Content management" menu, and the first three items in the "Site building" menu, but then it would cut off. Emptying the cache, or using Devel to rebuild the menus would bring everything back, but once I reloaded the page it would all disappear again. Also, this was only happening on my production site. My local dev site (using MAMP) exhibited none of these issues, even though I was copying over the exact same database and using git to ensure I had the exact same files.

After reading several issues here about caching, I started poking around the performance settings on my site. I disabled "Gzip page compression" and that appeared to have solved my problem.

Just now I manually edited admin_menu.module, changing line 413 to use strlen() instead of drupal_strlen(), as suggested in the patch from #7. I then enabled gzip page compression again and cleared my cache. I've been browsing the site and reloading pages with no apparent problems.

Marking this patch RTBC.

I did a little more poking around. Both my dev and production sites report that $GLOBALS['multibyte']=1, which would trigger drupal_strlen() to use the mb_strlen() function. However, if I change drupal_strlen() to mb_strlen(), the result still works on my local dev while failing on my production site. I assume this means that, on my production server, Admin Menu thinks it's dealing with a multibyte string, when in fact it isn't, so it comes up short on its character count.

Using firebug to view the response headers, my dev site reports Content-Length=7691, whether using mb_strlen() or strlen(). However, my production site reports Content-Length=7683 when using strlen(), but only 5389 when using mb_strlen().

Thanks for testing, @jstoller!

Hm. Apparently, Drupal core does not add any Content-Length HTTP header at all for cached page responses.

Any chance you could test whether we can simply remove that header entirely?

OK. I tried commenting out line 413 entirely and the menu kept working on both my local and remote servers, so I guess we can remove it. When I checked the response headers in Firebug, I confirmed that there was no Content-Length specified on my remote server, but the local MAMP server still came back with Content-Length=7693. I don't know what that means, but there you go.

Thanks for reporting, reviewing, and testing! Committed attached patch to 6.x-3.x.

A new development snapshot will be available within the next 12 hours.