Open Radar

 
Summary:
Windows with an alpha value other than 1.0, configured to join all desktops, flicker when switching between desktops.

Steps to Reproduce:
1. Compile and run the attached Test app. It shows a transparent window on all spaces in the background (underneath other windows).
2. Switch to an empty desktop. The Test window will be there too. Note that for a moment the window draws with no transparency.
3. Switch to a desktop with some other apps in it using a direct keyboard shortcut (e.g. don't use a keyboard shortcut for moving to the left or right space, but one that takes you directly to a specific space, like ctrl-1). Note that for a moment the Test window shows on top of all other windows.

Expected Results:
In step 2, the expected result is that the window draws with the correct amount of transparency the whole time.

In step 3, the expected result is that the window draws underneath all other windows the whole time.

Actual Results:
In step 2, the window draws with the wrong alpha value for a moment.

In step 3, the window draws at the wrong level/z-index for a moment (and probably also with the wrong alpha value, but it's hard to see since it's fast.)

Version:
OS X 10.8.5

Notes:


Configuration:
The problem is more pronounced with a Thunderbolt display attached to a laptop, presumably because redraws get a little slower.