+jamescook@ for thoughts.

For 3, there are two animations: transform and opacity.
When shrinking the window from maximized window to smaller size window, there is NO opacity change, settings.observer::OnImplicitAnimationsCompleted get called immediately even the transform animation is still on-going.

I am trying to figure out why.

Thanks to Oshima, item 3 is not a bug. It depends where I add the observer to the ScopedLayerAnimationSettings. I need to add observer before I set transform animation.

Removed the item 3 in the description.
I will fix the item 1 first.

Animating transient window position seems fine.

Or frankly, not fixing one or both of these isses seems OK. They seem like pretty rare scenarios.

I have a fix for animating transient window. But in this fix, the transient window will be applied the same scale effect, which may look weird (The transient window always has the same size). please see the attached video.

oshima@, WDYT? If we want to only scale the parent window, not the transient window, it will become complicated to calculate the initial position of the transient window.

Deleted: TransientWindowAnimation.webm 6.8 MB

	TransientWindowAnimation.webm 6.8 MB View Download

+varkha@ who implement similar effect in overview mode.

I might want to reuse the code TransientDescendantIterator[Range] in scoped_transform_overview_window.cc. [1]
[1] https://cs.chromium.org/chromium/src/ash/wm/overview/scoped_transform_overview_window.cc?l=48&rcl=096cf059ac9ed4b9da1b2dfb6235717859d1c941

Do you think it is ok to move the class in a window util file if I end up need to reuse the code?

drive-by comment - scaling the transient looks kind of weird to me

Put this back to queue if we want to improve this. And lower the priority.