Invisible strategy for transitions (or data-open attribute)

[aaronadamsCA]

I'd like some way to accomplish an "invisible" transition strategy, so I can set visibility: hidden instead of display: none while an element is not shown.

My use case is transitions between different-sized elements. My only choices today are RenderStrategy.Unmount and RenderStrategy.Hidden, neither of which will hold space when an element is no longer shown.

If you were doing this in a major version, I'd say the best headless solution would be a data-open attribute to let us set data-open:hidden or data-open:invisible depending on our specific needs.