10.4: Avoid a fast user switching color profile bug

Jan 09, '06 07:10:00AM

Contributed by: atverd

Tiger only hintThere is a nasty bug in Tiger related to custom color profiles. Specifically, when you have a custom profile assigned to your display and use fast user switching, the profile will get reset and a "Generic RGB Profile" assigned instead. As a result, the display looks blindingly bright, colors get shifted, and it's practically impossible to work with the computer after that. Display settings don't work either -- when you try to return the old profile, the system just beeps and doesn't do anything. If you press the Calibrate button, it will return an error about a lost profile and exit. A reboot, however, will return everything to normal -- at least until you use fast user switching again.

This bug is old -- it's been known since 10.4.1 at least. It doesn't look like Apple cares to fix it at all in the short term, even though it's 100% reproducible and a lot of people are reporting it on different forums. Because of this bug, I stopped using fast user switching at all. Howevever, I recently absolutely needed the feature, so I started to dig deeper and after some investigation, I found that an application named "DMProxy" is the culprit.

I have no idea what this thing does, but it's obviously related to the CoreGraphics framework, as it resides here: /System -> Library -> Frameworks -> ApplicationServices.framework -> Versions -> A -> Frameworks -> CoreGraphics.framework -> Versions -> A -> Resources.

To make a long story short, just launch DMProxy from the Terminal without any parameters when you get "the blinding screen of death," and everything immediately returns to normal. Probably the simplest way to call it is just to drag-and-drop it to each of your accounts' Login Items (in System Preferences: Accounts, Login Items tab), and it will be called automatically every time when you log in. It will fix the problem completely -- the display profiles panel will work again, and the Calibrate button will call the built in display calibration utility. So far no side effects noted, but if you find something, let us know here!

[robg adds: I can't duplicate this problem on my PowerBook; switching between two users, both of whom have distinct color profiles, didn't cause the problem to occur. I'm posting the hint, though, as I have seen it reported in a number of places, so it does seem somewhat widespread. Please comment if you can provide additional details...]

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Mac OS X Hints
http://hints.macworld.com/article.php?story=20060103162354164