Mac OS X 10.4 bug with fast user switching and display profiles: It’s the input menu

Posted by Pierre Igot in: Macintosh
September 13th, 2006 • 9:44 am

After some further testing on my semi-dead G5 Quad, I have finally been able to discover what appears to be causing the bug with fast user switching in Mac OS X 10.4.x, which triggers a color/brightness shift and causes the “Color” tab of the “Displays” preference pane to cease to work properly.

I managed to identify the source of the problem by removing my entire “Preferences” folder inside my home library folder, and then restoring the preference files bit by bit. Removing the entire “Preferences” folder eliminates the problem. In other words, if you are a Mac OS X 10.4 user experiencing the bug with fast user switching, if you drag your entire “Preferences” folder from your home library folder to your desktop, then log out, then log back in, and then use fast user switching, the color shift and “Displays” failure will no longer happen.

If, however, you move all your preference files back inside your “Preferences” folder inside your home library folder, then the problem reappears.

So clearly, the problem is with one of the preference files. But which one? By restoring my preference files in batches, It didn’t take me too long to find the culprit: It’s the file called “” If you just remove that file from your “Preferences” folder inside your home library folder, then log out and log back in and then try to use fast user switching, you’ll notice that the color shift and “Displays” failure no longer occur.

If you restore that “,” log out and log back in, the problem will reoccur. And it will reoccur even on a machine with a single monitor. It doesn’t require a dual-monitor set-up. And I am also pretty sure that it doesn’t require the use of customized color profiles. (I was also able to reproduce the bug on a MacBook with the default color profile.)

I was actually able to narrow the source of the bug down even further. All you need to do in order to make the problem reoccur (at least on my system) is to check the option labelled “Show input menu in menu bar” in the “Input Menu” tab of the “International” preference pane.

I found this out because I knew that the “” preference file contains settings involving the “International” preference pane. And I knew that because I am a long-time Spell Catcher X user, and Spell Catcher X works through that input menu.

So effectively in order to avoid the bug with displays and fast user switching, you need to not use the input menu. Sadly, for Spell Catcher X users, this is not an option. We have to use the input menu, because that’s how Spell Catcher X’s features can be accessed. I was also able to verify that Spell Catcher does run with the input menu hidden, but the bug with displays and fast user switching still occurs when the input method is Spell Catcher, even if the input menu is hidden.

In other words, in order to avoid the bug, you have to avoid using Spell Catcher altogether, and keep the input menu invisible. I am afraid this is not an option for me, so all I can do is report my findings to Apple and hope that they fill fix the bug in a future system update. But maybe there are other Mac users out there affected by the bug who are not Spell Catcher users and who just happen to have the input menu visible in their menu bar. For them, hiding the input menu will be enough to eliminate the bug.

14 Responses to “Mac OS X 10.4 bug with fast user switching and display profiles: It’s the input menu”

  1. ssp says:

    Great effort. I hope this analysis narrows down things far enough for Apple to be able to solve the problem.

    SystemUIServer seems to be a particularly shaky bit of software anyway. Ever since X.4 I have menu extras disappearing at most restarts… another thing that makes me hate restarts.

  2. Pierre Igot says:

    Yes, SystemUIServer does seem pretty shaky. While I was fooling around the pref files and removing/restoring the pref file for that particular (background) application, I would sometimes log in and the right-hand side of the menu bar would stay blank for a long time after log in, even when the rest of the system was running fine. Then it would finally appear.

  3. danridley says:

    I can’t reproduce this. I have a MacBook with 10.4.7, two calibrated displays (the built-in LCD and an Acer AL1916W), and the input menu visible. I don’t use Spell Catcher X, or anything non-Apple that installs into the input menu. (I do have some InputManager bundles installed — Ecamm, Smart Crash Reports, and SIMBL. However, none of these actually install into the input menu.)

    Are you sure this is an input menu bug, and not a Spell Catcher X bug?

  4. Pierre Igot says:

    Dan: I think there are reports of people who have the problem and do not use Spell Catcher X. It’s possible that the presence of SCX contributes to the problem, but I don’t think it’s actually caused by SCX. Maybe it has to do with which items are actually visible in the input menu. Did you try adding the char palette or keyboard viewer to the menu? Or making the source name visible? Maybe it’s one of these options. I’ll have to do more testing.

  5. matsw says:

    On my system, the color profile bug happens with or without the input menu in the menu bar.

    I do not believe it has anything to do with systemuiserver.plist. All this file contains is the position of the active menu extras, and the position and size of a few warning windows.

  6. Pierre Igot says:

    Dan: Is the source name visible in your input menu? When I make the source name invisible after making the input menu visible, the bug does not occur. But when I make the source name visible, the bug occurs. So maybe that’s an additional requirement to make the bug occur.

  7. Pierre Igot says:

    Matsw: On my system, removing the systemuiserver.plist file eliminates the bug. So it might not be the sole cause of the problem, but it is most definitely involved somehow.

  8. ssp says:

    I have seen this problem as well. I usually (i.e. if SystemUIServer hasn’t decided to not display it once again) have the input menu visible with just the flag being shown in the menu bar. I don’t have and never had Spell Catcher installed.

    In my experience the colour profile problem doesn’t appear every single time I switch users.

    Just my €0,02.

  9. matsw says:

    indeed, it does not happen every time, and that is what makes it difficult to isolate its cause.

  10. Pierre Igot says:

    I think we’re getting closer, though. See this post for more information.

  11. Evan Gross says:

    I think this would be a SystemUIServer bug – maybe an input menu bug (/System/Library/CoreServices/Menu Extras/, certainly not even remotely anything to do with Spell Catcher X.

    I can reproduce it with the input menu visible, containing only the US English keyboard layout.

    Whether the input source name is shown or not doesn’t matter.

    The plot thickens…

  12. jhall_3rd says:

    hmm – I don’t use spell catcher X and i have the int’l input menu disabled (it’s actually never been enabled) — I still have this user switching bug. I really don;t believe this is the issue! Have a look at the postings regarding DMProxy…

  13. Pierre Igot says:

    I’ve posted updates on this bug since the initial post. The input menu is involved, as is the entire right-hand side of the menu bar. Apparently, it depends on how many menu extras you have in there. The IM is just one of them.

  14. rob says:

    Hi Just to let you know I have a problem where my screen washes out. Its made my life a totaly misery. Anyway not technical at all so no chance of investigating or fixing. However searched around and found you guys. I discovered that when I view a pdf via ‘Preview’ software, then slideshow it (the pdf) my screen goes back to normal when I click out. I’d love to rectify my issue so will keep watching this space. cheers rob.

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