DRY pass #2, batch 8, F20: one foreground observer, one foreground latch (#5372)

FlushOnStop was ForegroundTransitions with only its ON_STOP half, so it goes
and the editor calls ForegroundTransitions(onBackground = flush); both halves
now default to nothing, dropping three onBackground = {}. AutomaticUpdate and
AutomaticSync each kept a wanted flag set on the way in and consumed in a
LaunchedEffect once ready; that latch is OnEachForeground(ready, onBackground,
act), with each caller's ready and its reason kept where they were.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/inkwell/MainActivity.kt

@@ -430,7 +430,7 @@ private fun ReminderAlarms(core: Inkwell) {
             refresh()
         }
 
-    ForegroundTransitions(onForeground = { refresh() }, onBackground = {})
+    ForegroundTransitions(onForeground = { refresh() })
 
     LaunchedEffect(Unit) {
         // TIRAMISU is where POST_NOTIFICATIONS became a runtime permission. Below
@@ -461,17 +461,9 @@ private fun AutomaticUpdate(
     linked: Boolean,
     onCheck: () -> Unit,
 ) {
-    var wanted by remember { mutableStateOf(false) }
-    ForegroundTransitions(onForeground = { wanted = true }, onBackground = {})
-
-    LaunchedEffect(wanted, linked) {
-        if (!wanted || !linked) return@LaunchedEffect
-        // Consumed here, so this fires once per trip to the foreground however many
-        // times the effect restarts. There is no suspension point before the call, so
-        // the block completes before the recomposition that would cancel it.
-        wanted = false
-        onCheck()
-    }
+    // Waits for a link rather than dropping the trip: linking a device while the app is
+    // in front checks as soon as it is linked.
+    OnEachForeground(ready = linked, act = onCheck)
 }
 
 /**
@@ -508,28 +500,18 @@ private fun AutomaticSync(
         if (state.linked && enabled) SyncSchedule.enable(context) else SyncSchedule.disable(context)
     }
 
-    var wanted by remember { mutableStateOf(false) }
-    ForegroundTransitions(
-        onForeground = { wanted = true },
+    // Ready once `loading` is done, so the decision waits for the stored link to be
+    // READ. At first composition `linked` is still false because nothing has looked in
+    // the database yet, and acting on that would skip the sync on every cold start.
+    OnEachForeground(
+        ready = !state.loading,
         onBackground = {
             // Unsent work follows the person out of the app. Without this, a note
             // written on a phone that then goes into a pocket for the night does
             // not reach the desktop until the app is opened again by hand.
             if (enabled && state.linked && state.pending) SyncSchedule.pushSoon(context)
         },
-    )
-
-    // Keyed on `loading` so the decision waits for the stored link to be READ. At
-    // first composition `linked` is still false because nothing has looked in the
-    // database yet, and acting on that would skip the sync on every cold start.
-    LaunchedEffect(wanted, state.loading) {
-        if (!wanted || state.loading) return@LaunchedEffect
-        // Consumed here, so this fires exactly once per trip to the foreground
-        // however many times the effect restarts. Writing a key from inside the
-        // effect does restart it — but there is no suspension point between here
-        // and the call below, so the block runs to completion before the
-        // recomposition that would cancel it can be scheduled.
-        wanted = false
+    ) {
         val worthIt = state.pending || olderThan(state.status?.lastSyncAt, STALE_MINUTES)
         if (enabled && state.linked && worthIt) onSync()
     }

android/app/src/main/java/com/fabledsword/inkwell/ui/FlushOnStop.kt

@@ -1,36 +0,0 @@
-package com.fabledsword.inkwell.ui
-
-import androidx.compose.runtime.Composable
-import androidx.compose.runtime.DisposableEffect
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.rememberUpdatedState
-import androidx.lifecycle.Lifecycle
-import androidx.lifecycle.LifecycleEventObserver
-import androidx.lifecycle.compose.LocalLifecycleOwner
-
-/**
- * Run [flush] when the app goes to the background.
- *
- * `ON_STOP` rather than `ON_PAUSE`: pause also fires when a dialog opens over the
- * activity, which would save mid-sentence for no reason. The lambda goes through
- * `rememberUpdatedState` so the observer — registered once — always calls the
- * CURRENT one; captured directly it would hold the first composition's empty text
- * forever and save that over a full note.
- *
- * Shared by the editor and the capture sheet. Both are places where text exists
- * only in a composable until something writes it down, and the process can be
- * killed while backgrounded without either of them being told again.
- */
-@Composable
-fun FlushOnStop(flush: () -> Unit) {
-    val current by rememberUpdatedState(flush)
-    val owner = LocalLifecycleOwner.current
-    DisposableEffect(owner) {
-        val observer =
-            LifecycleEventObserver { _, event ->
-                if (event == Lifecycle.Event.ON_STOP) current()
-            }
-        owner.lifecycle.addObserver(observer)
-        onDispose { owner.lifecycle.removeObserver(observer) }
-    }
-}

android/app/src/main/java/com/fabledsword/inkwell/ui/ForegroundTransitions.kt

@@ -2,8 +2,12 @@ package com.fabledsword.inkwell.ui
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import androidx.lifecycle.compose.LocalLifecycleOwner
@@ -11,28 +15,31 @@ import androidx.lifecycle.compose.LocalLifecycleOwner
 /**
  * Calls back when the app comes to the front and when it leaves.
  *
- * `ON_START`/`ON_STOP` and not `ON_RESUME`/`ON_PAUSE`, which is the same choice
- * the editor's save-on-leave makes for the same reason: resume and pause fire for
+ * `ON_START`/`ON_STOP` and not `ON_RESUME`/`ON_PAUSE`: resume and pause fire for
  * anything that merely covers the window — a permission dialog, the notification
- * shade — and a sync per shade-pull is not automatic sync, it is a stutter.
+ * shade — and a sync per shade-pull is not automatic sync, it is a stutter, just as
+ * a save per dialog would save the editor mid-sentence.
  *
  * A single-Activity app, so the Activity's lifecycle is the app's. If a second
  * Activity is ever added this needs `ProcessLifecycleOwner` instead, or rotating
  * between them will read as leaving and returning.
  *
- * Two callers, wanting opposite halves of it: automatic sync uses the return to
- * decide whether to fetch, and the reminder notice uses it to re-read a
- * permission the person may have just changed in the system settings.
+ * Callers want different halves of it: automatic sync uses both, the reminder
+ * notice and the update card use the return to re-read a permission the person may
+ * have just changed in the system settings, and the editor uses the leaving to
+ * write down text that otherwise exists only in a composable — the process can be
+ * killed while backgrounded without it being told again.
  *
  * Both callbacks go through [rememberUpdatedState]: the observer is registered
  * once, and without it the lambda would keep reading the first composition's
  * state forever — deciding whether to push unsent notes from a snapshot taken
- * before any note existed.
+ * before any note existed, or saving the first composition's empty text over a
+ * full note.
  */
 @Composable
 fun ForegroundTransitions(
-    onForeground: () -> Unit,
-    onBackground: () -> Unit,
+    onForeground: () -> Unit = {},
+    onBackground: () -> Unit = {},
 ) {
     val forward by rememberUpdatedState(onForeground)
     val away by rememberUpdatedState(onBackground)
@@ -50,3 +57,29 @@ fun ForegroundTransitions(
         onDispose { owner.lifecycle.removeObserver(observer) }
     }
 }
+
+/**
+ * Run [act] once per trip to the front, as soon as [ready] holds.
+ *
+ * A trip that arrives before [ready] is held, not dropped: it runs when [ready]
+ * turns true. [onBackground] is passed through to [ForegroundTransitions].
+ *
+ * The trip is consumed inside the effect, so [act] fires once however many times
+ * the effect restarts. Writing a key from inside the effect does restart it — but
+ * there is no suspension point between consuming it and the call, so the block
+ * runs to completion before the recomposition that would cancel it is scheduled.
+ */
+@Composable
+fun OnEachForeground(
+    ready: Boolean,
+    onBackground: () -> Unit = {},
+    act: () -> Unit,
+) {
+    var wanted by remember { mutableStateOf(false) }
+    ForegroundTransitions(onForeground = { wanted = true }, onBackground = onBackground)
+    LaunchedEffect(wanted, ready) {
+        if (!wanted || !ready) return@LaunchedEffect
+        wanted = false
+        act()
+    }
+}

android/app/src/main/java/com/fabledsword/inkwell/ui/NoteEditorScreen.kt

@@ -142,7 +142,7 @@ fun NoteEditorScreen(
     BackHandler(onBack = leave)
 
     // The system picker, for any type: a note can carry a PDF as readily as a photo.
-    // Leaving for it stops this screen, so FlushOnStop has already saved the text by
+    // Leaving for it stops this screen, so the flush on leaving has already saved the text by
     // the time the files come back.
     val pickFiles =
         rememberLauncherForActivityResult(ActivityResultContracts.GetMultipleContents()) { uris ->
@@ -152,7 +152,7 @@ fun NoteEditorScreen(
     // Leaving the APP is not closing the editor, so the text has to be saved
     // without the screen being torn down. Losing a paragraph to an incoming call
     // is exactly the failure that makes someone stop trusting a notes app.
-    FlushOnStop(flush)
+    ForegroundTransitions(onBackground = flush)
 
     // The sheet shape, kept. `windowInsetsPadding` both insets the card below the
     // status bar AND consumes that inset, so the bar inside adds no second gap of
@@ -340,7 +340,7 @@ private fun EditorOverlays(
  * How long typing has to stop before the note is written.
  *
  * Long enough that a normal sentence is one write, short enough that nothing
- * meaningful is at risk if the app dies. The flush on close and [FlushOnStop] still
+ * meaningful is at risk if the app dies. The flush on close and on leaving the app still
  * cover the window between the last keystroke and this elapsing.
  */
 private const val AUTOSAVE_IDLE_MS = 1_000L

android/app/src/main/java/com/fabledsword/inkwell/ui/ReminderNotice.kt

@@ -48,7 +48,6 @@ fun ReminderNotice() {
             canNotify = notificationsAllowed(context)
             canBeExact = exactAllowed(context)
         },
-        onBackground = {},
     )
 
     if (canNotify && canBeExact) return

android/app/src/main/java/com/fabledsword/inkwell/ui/UpdateCard.kt

@@ -53,7 +53,7 @@ fun UpdateCard(
     // be up after someone granted it and came back, and the offer below it would
     // look blocked when it is not (family idea #5103, practice 9).
     var canInstall by remember { mutableStateOf(AppUpdate.canInstall(context)) }
-    ForegroundTransitions(onForeground = { canInstall = AppUpdate.canInstall(context) }, onBackground = {})
+    ForegroundTransitions(onForeground = { canInstall = AppUpdate.canInstall(context) })
 
     // The system answers an install through a BroadcastReceiver, which has no way
     // back into a view model. This is the seam.