macos - Widget "flip" behavior in Core Animation/Cocoa

Question

I'm trying to make a Card class that duplicates the behavior of Dashboard widgets in that you can put controls or images or whatever on two sides of the card and flip between them.

Layer backed views have a transform property, but altering that doesn't do what I would expect it to do (rotating the layer around the y axis folds it off to the left side).

I was pointed to some undocumented features and an .h file named cgsprivate.h, but I'm wondering if there is an official way to do this? This software would have to be shipped and I'd hate to see it fail later because the Apple guys pull it in 10.6.

Anyone have any idea how to do this? It's so weird to me that a simple widget thing would be so hard to do in Core Animation.

Thanks in advance!

EDIT: I can accomplish this behavior with images that are on layers, but I don't know how to get more advanced controls/views/whatever on the layers. The card example uses images.

Answer 1

Mike Lee has an implementation of the flip effect for which he has released some sample code. (Unfortunately, this is no longer available online, but Drew McCormack built off of that in his own implementation.) It appears that he grabs the layers for the "background" and "foreground" views to be swapped, uses a CATransform3D to rotate the two views in the animation, and then swaps the views once the animation has completed.

By using the layers from the views, you avoid needing to cache into a bitmap, since that's what the layers are doing anyways. In any case, his view controller looks to be a good drop-in solution for what you want.