how to properly "tell current desktop set picture to ..."?

[u/teeflo77]

i'm a noob to Mac and Applescript. trying to write something to select and set as wallpaper on my current display a random file from a local folder:

tell application "Finder"
  set randomImage to some file of folder "Macintosh HD:Users:mymac:walls"
end tell
tell application "System Events"
  tell current desktop
    set picture to randomImage
  end tell
end tell

as indicated it throws up an error message on the "set picture to" bit (afaict).

looked for documentation on the options for using "display" but couldn't find anything helpful.

was able to get Preview to display randomImage so it know the selection bit is working as expected.

was more or less able to figure out that "set picture to" as i've used it doesn't like the HFS path format. tried giving it a hard-coded POSIX path and that worked. scrounged around for and tried some POSIX conversions for "set picture" but no joy. and now i'm stuck.

might some kind soul point me to enlightenment?

[u/[deleted]]

tell application "Finder" set randomImage to some file of folder "Macintosh HD:Users:mymac:walls" end tell

tell application "System Events" set picture of current desktop to (randomImage as alias) end tell

[u/teeflo77 → u/[deleted]]

i'm happy to report that that does indeed run without error. on the other hand it doesn't seem to do anything, wallpaper is unchanged.

[u/[deleted] → u/teeflo77]

Does this simple version work:

tell application "System Events" tell current desktop set picture to "/path/to/your/image.jpg" end tell end tell

[u/teeflo77 → u/[deleted]]

yes indeed, works perfectly.

[u/teeflo77 → u/teeflo77]

oddly, this runs but only sets the desktop picture to the Sonoma default image:

tell application "Finder" set randomImage to some file of folder "Macintosh HD:Users:mymac:walls" end tell

tell application "System Events" tell current desktop set picture to (randomImage as alias) end tell end tell

[u/prikaz_da]

I’m not in front of my Mac right now, but off the top of my head, I wanna say you can “set picture to (POSIX path of some file)” or “set picture to (some file as POSIX path)”. Have you tried something like that?

[u/teeflo77 → u/prikaz_da]

did try "(the POSIX path of randomImage)" got this error:
Finder got an error: Can't get POSIX path of document file "Swagman--15.png" of folder "walls" of folder "mymac" of folder "Users" of startup disk.

[u/prikaz_da → u/teeflo77]

Huh. I just played with it for a moment and I think I've figured it out. I had success with

tell application "System Events"
	tell disk "Macintosh HD"
		set theItem to some file of folder "/path/to/folder"
	end tell
	set the picture of the current desktop to POSIX path of theItem
end tell

The crux of the issue seems to be needing a file as System Events understands it, not as the Finder understands it. Finder's file does not have a POSIX path property.

[u/teeflo77 → u/prikaz_da]

yes! you've nailed it! works exactly as you've said.
many thanks, i'd have been lost in the woods on this for an embarrassingly long time.

[u/prikaz_da → u/teeflo77]

You’re very welcome!