@startuml

skinparam object {
  backgroundColor White
  borderColor Black
  arrowColor Black
}

skinparam note {
  backgroundColor LightYellow
  borderColor Black
}

hide footbox

title Lifecycle of a Wrapper

participant App as app << ts >> #E3C800
participant "QWindow.ts" as qwindowts << ts>> #E3C800
participant "QScreen.ts" as qscreents << ts>> #E3C800
participant "WrapperCache" as wrappercachets << ts>> #E3C800
participant "QWindowWrap" as qwindowwrap << cpp >>
participant "QScreenWrap" as qscreenwrap << cpp >>
participant "WrapperCache" as wrappercachecpp << cpp >>
participant "QWindow" as qwindow << cpp >> #D5E8D4
participant "QScreen" as qscreen << cpp >> #D5E8D4


== Wrapper construction ==

activate qscreen
app --> qwindowts: QWindow.screen()
qwindowts --> qwindowwrap: screen()
qwindowwrap --> qwindow: screen()
qwindow --> qwindowwrap: QScreen instance
qwindowwrap --> wrappercachecpp: get<QScreen, QScreenWrap>()
note over wrappercachecpp
  Checks wrapper cache
end note
wrappercachecpp --> qscreenwrap: new()
activate qscreenwrap
qscreenwrap --> wrappercachecpp: QScreenWrap instance
wrappercachecpp --> qscreen: connect to destroy signal
wrappercachecpp --> qwindowwrap: QScreenWrap instance
qwindowwrap --> qwindowts: QScreenWrap instance
qwindowts --> wrappercachets: get<QScreen>(QScreenWrap instance)
wrappercachets --> qscreents: new(QScreenWrap instance)
activate qscreents
qscreents --> wrappercachets: QScreen.ts instance
wrappercachets --> qwindowts: QScreen.ts instance
qwindowts --> app: QScreen.ts instance

note across: The app can use the QScreen wrap and run.

== Qt object destruction ==
note over qscreen
  Qt decides to destroy
  the QScreen instance
end note
qscreen --> wrappercachecpp: destroy signal
destroy qscreen
wrappercachecpp --> wrappercachets: destroy callback

note over wrappercachecpp
  WrapperCache removes
  references to the wrapper
  and Qt object from cache.
end note

wrappercachets --> qscreents: null the ref to QScreenWrap
note over wrappercachets
  WrapperCache.ts removes
  references to the QScreen.ts
  instance and QScreenWrap
end note

destroy qscreenwrap
note over qscreenwrap
  V8's GC will destroy
  this automatically
end note

app --> qscreents
note over app
  Any use of QScreen.ts
  will hit the null reference
  and throw a JS exception.
end note
app --> qscreents

destroy qscreents
note over qscreents
  V8's GC will destroy
  this automatically
end note

@enduml