IssueTracker

Description:

In the case of Composition.setContent() I would like to call applyChanges() separately after the composition phase completes, to catch up with initialization work that runs in the background concurrently with the composition phase. The results from concurrent initialization are made available via a UI thread Looper callback, and are used in the Applier. Currently there is no break between composition and applyChanges(), so I cannot receive results from concurrent initialization on the UI thread; I am forced to sequentially first complete separate initialization, then run composition + applyChanges().

Use Case:

This feature would help with reducing GoogleMap initialization delays in the android-maps-compose GitHub library project. The library controls the GoogleMap MapView via a child composition to the standard Android Compose UI composition. MapView.getMapAsync(callback) is called to initialize the GoogleMap and receive a GoogleMap object via a UI thread Looper callback; initialization work is expected to occur away from the app process main thread. The GoogleMap object is not needed during child composition, just for applyChanges(), so it would be useful to not delay the potentially expensive initial child composition (possibly large child composition content hierarchy) by first having to wait for a callback.

I have explored various alternatives and do not see another viable non-sequential approach.

This issue relates to https://github.com/googlemaps/android-maps-compose/issues/501