If box-shadow is applied to an element inside a CSS multi-column, the shadow is cut off at the column's boundary.
Testcase to follow demonstrating box-shadow working correctly for floated elements but not elements in columns.
Tested on the Windows Safari 3 Beta (522.11.3). Probably not platform specific but I don't have a Mac to test against, sorry.
Created attachment 15018 [details]
Testcase for box-shadow boundary on elements in multi-column
I believe this is part of the "layers ignore columns" problem.
No, this is just a clipping problem. At one point the spec said to treat overflow like it was hidden on columns. I don't think it says that now though.
Yes, I find this quite frustrating.
Here's an example: http://labs.jensimmons.com/examples/image-gallery-multicolumn.html
See how all the shadows from the top of the boxes are placed in the bottom of the previous column? And how the shadow from the bottom if the box of the longest column is placed at the top of the previous column? Bug.
Here's a photo to be more obvious: https://monosnap.com/file/wCjt9v38xTPPTmGQJ8t42jvEgqioEM.png
It's one of the many little multicolumn bugs that prevent people from trusting or using multicolumn.
This happens in Mac Safari, iOS Safari, and Chrome (old webkit).
It appears this now fixed in Chrome and Firefox, probably due to recent updates, as it was still broken in all browsers (IIRC) just a couple of years ago.
Screenshots for all three can be found here, and each is labeled with the name of the browser from which the screenshot was taken: https://imgur.com/a/HJBUiZW
This is using Safari Technology Preview Release 161 (Safari 16.4, WebKit 186220.127.116.11)