System Preferences caching Swift libraries causing screensaver to display "You cannot use ... screen saver with this version of OS X."

Number:rdar://25569037 Date Originated:06 April 2016
Status:Open Resolved:
Product:OSX Product Version:10.11.4
Classification: Reproducible:YES
When you open a screensaver written in Swift in System Preferences it seems to cache the Swift libraries that are contained within the screensaver. If you then try to open another screensaver written in Swift, if it was written against another version of the Swift libraries System Preferences will display an error message "You cannot use the  XXX saver with this version of OS X."

Steps to Reproduce:
1. Download the binary version 1.2 Beta 5 of the Aerial screensaver.
2. Download the binary version 0.5 of the Clock screensaver
3. Download the iOS Saver screensaver from
4. Install the three binaries to "~/Library/Screen Savers"
5. Open System Preferences
6. Select Desktop & Screen Saver
7. Select Aerial - it will load and preview successfully
8. Select Clock - it will display the "You cannot use ... screen saver with this version of OS X." error message
9. Select iOS Saver - it will display the error message

To prove what I'm saying about it being the bundled Swift libraries.
1. Download the source for Aerial and Clock using the "Download ZIP" links at and
2. Compile both (which results in bundles that contain the same Swift libraries)
3. Copy both to "~/Library/Screen Saver"
4. Open System Preferences and try switching between them. It should work reliably as they are using the same version of the Swift libraries.

Expected Results:
I would expect to be able to select different screen savers and not see the error message

Actual Results:
What I think is happening... System Preferences is loading the Swift libraries that are bundled within the first selected screensaver. It then attempts to use them with the subsequent Swift screen savers and displays the "You cannot use ... screen saver with this version of OS X." error message because they've been compiled against a different version.



Did apple respond?

As of today it has been 614 days with nary a peep from Apple. Absolute silence. At least they haven't closed the call. I guess that's a positive. :D

By alistairmcmillan75 at Dec. 11, 2017, 10:36 a.m. (reply...)

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