How do I add shadows to a window when its undecorated attribute was set to true?

[Adiudiu]

No description provided.

[AlexeyTsvetkov]

@Adiudiu please provide more context:

• What is the expected result?
• What is the actual result?
• Your environment: kotlin version, compose version, jdk version, operating system name and its version?
• Add relevant screenshots & reproduction sample if possible.

[Raphael-N]

Maybe I can add some more details since I'm facing the same issue.

Expected Result
My use case is that I would like to build a Spotlight/Alfred/Raycast style input window. These are all undecorated but have an (OS made) DropShadow on MacOS. This behaviour would be the expected result.

Actual Result
I can build an undecorated window with transparent background that behaves in a similar way but it doesn't have a shadow which is a bit unusual on MacOS.

Environment
I am working on Kotlin 1.9.0, compose version 1.4.3, jdk version 17.0.3.1, MacOS Ventura 13.5

Additional Info
It is actually not trivial to produce this behaviour with AppKit on MacOS. It can be achieved by leaving decorations on but then making the titlebar transparent, making the space of the titlebar space usable by the app and hiding the close, minimize and maximize buttons. With that, it looks something like this:

It would be great to have some more access to the detailed window behaviour in each operating system but I am not sure how and if this is achievable.

[mahozad]

@Raphael-N I provided a solution for native shadows and animations for Windows:

• Missing animations when minimizing/maximizing/restoring undecorated window #3388 (comment)

Maybe it will be handy for you as well.