There are multiple places in the codebase we present a conversation.
We used to have some very conservative machinery around how this was done, for
fear of failing to present the call view controller, which would have left a
hidden call in the background. We've since addressed that concern more
thoroughly via the separate calling UIWindow.
As such, the remaining presentation machinery is overly complex and inflexible
for what we need.
Sometimes we want to animate-push the conversation. (tap on home, tap on "send message" in contact card/group members)
Sometimes we want to dismiss a modal, to reveal the conversation behind it (contact picker, group creation)
Sometimes we want to present the conversation with no animation (becoming active from a notification)
We also want to ensure that we're never pushing more than one conversation view
controller, which was previously a problem since we were "pushing" a newly
constructed VC in response to these myriad actions. It turned out there were
certain code paths that caused multiple actions to be fired in rapid succession
which pushed multiple ConversationVC's.
The built-in method: `setViewControllers:animated` easily ensures we only have
one ConversationVC on the stack, while being composable enough to faciliate the
various more efficient animations we desire.
The only thing lost with the complex methods is that the naive
`presentViewController:` can fail, e.g. if another view is already presented.
E.g. if an alert appears *just* before the user taps compose, the contact
picker will fail to present.
Since we no longer depend on this for presenting the CallViewController, this
isn't catostrophic, and in fact, arguable preferable, since we want the user to
read and dismiss any alert explicitly.
// FREEBIE
I removed this earlier - but turns out we still need this strong
reference, even though we're now using willDissapear instead of
didDissappear.
// FREEBIE
Text of the exception is:
"Impossible to set up layout with view hierarchy unprepared for constraint"
Since their container view is pinned to the top layout guide, this
should not change the layout.
// FREEBIE
