This article originally appeared in TidBITS on 2009-09-07 at 1:48 p.m.
The permanent URL for this article is: http://tidbits.com/article/10542
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Solve Snow Leopard's Screen Sharing Bug

by Glenn Fleishman

[Update: This bug appears to be fixed in 10.6.1 on some systems. In my tests, I no longer get the black screen error described below on one computer; on another, the problem remains.]

I'm addicted to remote access to my Macs. I have LogMeIn and Timbuktu Pro installed on most of the several computers I own or manage, in addition to using Leopard and now Snow Leopard remote access.

But Snow Leopard has thrown a spanner in the works. The first time I connected using built-in screen sharing, the remote screen was black (see this demonstration screencast [1] I made). I assumed I'd made an error, and tried other methods to no avail. I switched to LogMeIn, and the remote system was fine.

After some experimentation, I discovered the bug appears to be in Snow Leopard in the Screen Sharing application that handles connections via Bonjour, Back to My Mac (which uses Bonjour), and directly entered addresses. (The Screen Sharing program is hidden in /System/Library/CoreServices.)

The solution is tedious but works every time I've tried it. The View menu shows Full Quality (no lossy screen compression) or Adaptive Quality (lossy but faster display). Choosing either whichever quality option is not selected or - bizarrely - the currently selected view option, and the remote screen starts streaming.

Apple needs to fix this bug, which has occurred on every system I've updated to Snow Leopard, although I haven't heard vociferous complaints. Apple's support forums have reports from other puzzled and irritated users. There's no way to know how widely used remote screen sharing is. (Commenters on this article are divided: some aren't seeing the problem; others are on one or more of their computers.)

To initiate a screen sharing session in Leopard or Snow Leopard, you use the Sharing section of the Finder sidebar, selecting a server and then clicking the Share Screen button in the upper right of the Finder window. That button appears only if the Bonjour or Back to My Mac system has Screen Sharing enabled in the Sharing system preference pane. You can also launch the Screen Sharing program and enter an IP address, Bonjour name, or hostname.

Some portion of the Screen Sharing program's underlying framework is also used for screen sharing via iChat, but it's sufficiently different to avoid this problem.

I'm currently revising my book, Take Control of Screen Sharing in Leopard [2], to cover changes in Snow Leopard, and add details about screen sharing via Skype and using iPhone applications. If you have screen sharing questions or tips, please send them my way.

[1]: http://www.tidbits.com/resources/2009-09/screen_sharing_blackout.mov
[2]: http://www.takecontrolbooks.com/leopard-screen-sharing