Convert LogsViewModel.logs to SharedFlow

In order to address performance concerns over recreating lists.

app/src/main/java/de/westnordost/streetcomplete/screens/about/LogsFragment.kt

@@ -62,7 +62,7 @@ class LogsFragment : TwoPaneDetailFragment(R.layout.fragment_logs) {
     }
 
     private fun onClickShare() = viewLifecycleScope.launch {
-        val logText = viewModel.logs.value.format()
+        val logText = viewModel.logs.replayCache[0].format()
         val logTimestamp = LocalDateTime.now().toString()
         val logTitle = "${BuildConfig.APPLICATION_ID}_${BuildConfig.VERSION_NAME}_$logTimestamp.log"
 

app/src/main/java/de/westnordost/streetcomplete/screens/about/LogsViewModel.kt

@@ -4,9 +4,9 @@ import androidx.lifecycle.ViewModel
 import de.westnordost.streetcomplete.data.logs.LogMessage
 import de.westnordost.streetcomplete.data.logs.LogsFilters
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.SharedFlow
 
 abstract class LogsViewModel : ViewModel() {
     abstract val filters: MutableStateFlow<LogsFilters>
-    abstract val logs: StateFlow<List<LogMessage>>
+    abstract val logs: SharedFlow<List<LogMessage>>
 }

app/src/main/java/de/westnordost/streetcomplete/screens/about/LogsViewModelImpl.kt

@@ -11,14 +11,15 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.SharingStarted
-import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.callbackFlow
-import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.flow.shareIn
 import kotlinx.coroutines.flow.transformLatest
 import kotlinx.coroutines.plus
 import kotlinx.datetime.LocalDateTime
 import kotlinx.datetime.LocalTime
+import java.util.concurrent.CopyOnWriteArrayList
 
 class LogsViewModelImpl(
     private val logsController: LogsController,
@@ -55,21 +56,21 @@ class LogsViewModelImpl(
     }
 
     @OptIn(ExperimentalCoroutinesApi::class)
-    override val logs: StateFlow<List<LogMessage>> =
+    override val logs: SharedFlow<List<LogMessage>> =
         filters.transformLatest { filters ->
             // get prior logs into a backing state
             // There will be duplication regardless.
-            var logs: List<LogMessage> = logsController.getLogs(filters)
+            val logs = CopyOnWriteArrayList(logsController.getLogs(filters))
 
             // emit the logs for the first view
             emit(logs)
 
             // start listening to new logs
             getIncomingLogs(filters).collect {
-                logs = logs + it
+                logs.add(it)
                 emit(logs)
             }
-        }.stateIn(viewModelScope + Dispatchers.IO, SharingStarted.Eagerly, emptyList())
+        }.shareIn(viewModelScope + Dispatchers.IO, SharingStarted.Eagerly, 1)
 }
 
 private fun LogsController.getLogs(filters: LogsFilters) =