refactor: store more info about the transitions in the state

[satya164]

I'm working on reimplementing stacks and storing this info in the routes state makes things much simpler and allows me to get rid of something like the transitioner.

[ericvicenti]

Hey, sorry I didn't see this earlier! I wish we had discussed it before you spent time on this direction, because I think it is not such a good idea to keep transition info in the navigation state. The only reason isTransitioning is in the state is because we need to notify the event system when a transition is happening.

I really think the transition state should be handled by the navigator component, and not by navigation core. There are lots of edge cases that may crop up.. like, what if a navigator has a type of transition other than pushing or popping?

I see the isTransitioning stuff has been removed from Tab Router, which would break the "didFocus/didBlur" events in an animated tab navigator.

I actually think we should remove isTransitioning from the navigation state, and provide another API for transition completion instead (check the core/stack/native "transition-completion" branch to see how that would work)

[satya164]

Thanks for checking. I think it's okay coz this change was not a lot of work and I needed it to continue with my work regarding stack, so I couldn't wait. I can easily change it when we arrive at an alternative API.

The only reason isTransitioning is in the state is because we need to notify the event system when a transition is happening.

My use case is not for the event system. I'm rewriting stack navigator with reanimated: react-navigation/stack#131

The reasons I added this to router are:

• With reanimated, it's important to make sure only one route animates at a time to avoid some issues, so I need to keep track of which routes are transitioning: https://github.com/react-navigation/stack/blob/eb8aa9a34c946ea16839f9a11d87510d6d25939d/src/views/Stack/StackView.tsx#L45
• There is immediate: boolean to control if pushing/popping something should cause an animation or not, there's also replace which won't cause an animation. I need access to this info somehow. Since the view only receives the list of routes from the router, it’s not possible for it to know if a screen should animate or not when being added/being removed.

I see the isTransitioning stuff has been removed from Tab Router, which would break the "didFocus/didBlur" events in an animated tab navigator.

The tab navigator never used the isTransitioning property. So I think it shouldn't break anything. I think only stack navigator needed it.

I actually think we should remove isTransitioning from the navigation state, and provide another API for transition completion instead

I don't have any opinions about it, and it does seem better to remove this from the router. But the main issue is how can I access this info about which routes will animate from my component? I did take a look at the branch, but I think that's mostly related to the event system only.

[satya164]

Closing as we agreed on an alternative way.