fix(calendars): hide-only visibility reconcile, and keep it working read-only

Code review of the one-visibility-model fix (#75) found the reconciliation
reaching further than it should and the read-only case falling through it.

The migration switched calendars *on* to keep the upgrade invisible, but
"not disabled in Calendula" is the default for every calendar, including ones
the user deliberately hid in Google Calendar, Etar or DAVx5 — those would
reappear there and start firing reminders from a switch the user never touched.
Its sync_events guard didn't hold either: an ACCOUNT_TYPE_LOCAL calendar another
app created can sit at sync_events=0 while holding real device-local events. The
reconcile now only hides, and a one-time notice explains that visibility follows
the device and where to change it, instead of quietly rewriting other apps'
state.

Only READ_CALENDAR gates the app, so a read-only install could not write the
flag at all: every calendar it had switched off came back with its events and
its reminders, and the switch couldn't undo it. Those switch-offs are kept
app-side now (the retired disabled-set key, re-read under a new name), folded
into the visibility every consumer reads, and drained into the provider entry by
entry once WRITE_CALENDAR arrives — which also makes a part-applied run resumable
without re-applying a switch the user has since flipped by hand.

Also: restore the ReminderNotifier.post gate, the one path a snooze re-shown
from our own alarm passes; move the whole reconcile inside its try/catch, so a
damaged preferences file can't crash the process at launch; share one Calendars
query per provider tick across the flows that need it; and give the reworded
Settings hint new keys, so five locales stop rendering the retired app-only
wording.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,28 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Reminders now arrive for every calendar you have switched on. A calendar that
+  was hidden at system level — switched off in another calendar app, or never
+  switched on after being added — still showed its events and listed their
+  reminders in Calendula, but never notified: Android only schedules reminder
+  alarms for calendars marked visible, and Calendula kept its own separate
+  on/off list that had no say in it. There is now one switch: **Settings →
+  Calendars** turns a calendar on or off for the whole device, so what you see
+  and what reminds you can no longer disagree ([#75]).
+
+  Calendars you had switched off in Calendula are switched off here too on first
+  launch. Calendars that were already off — hidden in another calendar app, or
+  never switched on after being added — stay off, and Calendula says so once
+  rather than quietly switching them on for every app on your device; you can
+  turn any of them back on in Settings → Calendars.
+
+  If you gave Calendula read-only access to your calendars, the switch still
+  works: your choice is kept in the app until it can be written.
+
+  The drawer's filter is unchanged and still app-only: hiding a calendar there
+  tidies your view without silencing its reminders.
+
 ## [2.16.0] — 2026-07-24
 
 ### Added
@@ -1112,3 +1134,4 @@ automatically, with zero telemetry and no internet permission.
 [#42]: https://codeberg.org/jlmakiola/calendula/issues/42
 [#44]: https://codeberg.org/jlmakiola/calendula/issues/44
 [#70]: https://codeberg.org/jlmakiola/calendula/issues/70
+[#75]: https://codeberg.org/jlmakiola/calendula/issues/75

app/src/main/java/de/jeanlucmakiola/calendula/CalendulaApp.kt

@@ -4,6 +4,7 @@ import android.app.Application
 import dagger.hilt.android.EntryPointAccessors
 import dagger.hilt.android.HiltAndroidApp
 import de.jeanlucmakiola.calendula.data.backup.BackupScheduler
+import de.jeanlucmakiola.calendula.data.calendar.CalendarVisibilityReconciler
 import de.jeanlucmakiola.calendula.data.backup.BackupWorker
 import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesScheduler
 import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesSyncWorker
@@ -39,6 +40,24 @@ class CalendulaApp : Application() {
         )
         reconcileAutoBackup()
         reconcileSpecialDates()
+        reconcileCalendarVisibility()
+    }
+
+    /**
+     * Flush any calendar switch-off the app hasn't been allowed to write into
+     * the system's `Calendars.VISIBLE` yet — including the retired app-local
+     * "disabled calendars" set the upgrade inherits (#75). A no-op on a fresh
+     * install and in the steady state; a launch without the calendar permissions
+     * leaves the set pending, and granting them on the permission screen runs it
+     * there instead.
+     */
+    private fun reconcileCalendarVisibility() {
+        val deps = EntryPointAccessors.fromApplication(
+            this, CalendarVisibilityReconciler.Deps::class.java,
+        )
+        CoroutineScope(SupervisorJob() + Dispatchers.Default).launch {
+            deps.calendarVisibilityReconciler().run()
+        }
     }
 
     /**

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt

@@ -110,6 +110,32 @@ interface CalendarDataSource {
     /** Permanently delete a local calendar the app owns, with all its events. */
     fun deleteCalendar(id: Long)
 
+    /**
+     * Show or hide the calendar device-wide by writing `Calendars.VISIBLE` — the
+     * app's one visibility model (#75). `VISIBLE` also gates the provider's own
+     * reminder scheduling, so switching a calendar off here is what actually
+     * stops its notifications; switching it on is what brings them back.
+     * Writable by a plain app (one of the three columns the platform documents
+     * as such) and device-local — no sync adapter pushes it anywhere.
+     */
+    fun setCalendarVisible(id: Long, visible: Boolean)
+
+    /**
+     * Whether one calendar is currently switched on at system level, without
+     * reading every row — for the reminder gate, which sees a calendar id and
+     * nothing else. Null when the answer can't be had: no row (the calendar was
+     * deleted) or no read permission.
+     */
+    fun isCalendarVisible(id: Long): Boolean?
+
+    /**
+     * Whether the app holds `WRITE_CALENDAR`, i.e. may write
+     * [setCalendarVisible] at all. Read-only users (READ granted, WRITE denied)
+     * keep their calendar switches app-side instead — see
+     * [de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs.pendingDisabledCalendarIds].
+     */
+    fun canWriteCalendars(): Boolean
+
     /**
      * Create a local calendar tagged as the special-dates mirror for [type]
      * (a marker in `CAL_SYNC2`); returns its `Calendars._ID`. Otherwise a normal
@@ -373,6 +399,40 @@ class AndroidCalendarDataSource @Inject constructor(
         if (deleted == 0) throw WriteFailedException("delete calendar id=$id")
     }
 
+    /**
+     * Addressed by appended id on the plain (non-sync-adapter) Calendars URI,
+     * one calendar per call. Both parts are load-bearing:
+     * `CalendarProvider2.updateInTransaction` short-circuits to a raw database
+     * update unless the selection is `_id=…`, skipping the dirty marking *and*
+     * the `checkNextAlarm()` reschedule — i.e. an `_id IN (…)` batch would write
+     * the flag but never re-arm the reminder alarms this write exists to
+     * trigger. The sync-adapter URI is avoided so the write also applies to
+     * synced calendars, which is where the bug bites.
+     */
+    override fun setCalendarVisible(id: Long, visible: Boolean) {
+        val values = ContentValues().apply {
+            put(CalendarContract.Calendars.VISIBLE, if (visible) 1 else 0)
+        }
+        val rows = resolver.update(
+            ContentUris.withAppendedId(CalendarContract.Calendars.CONTENT_URI, id),
+            values, null, null,
+        )
+        if (rows == 0) throw WriteFailedException("set calendar visibility id=$id")
+    }
+
+    override fun isCalendarVisible(id: Long): Boolean? {
+        if (!hasCalendarPermission()) return null
+        return resolver.query(
+            ContentUris.withAppendedId(CalendarContract.Calendars.CONTENT_URI, id),
+            arrayOf(CalendarContract.Calendars.VISIBLE),
+            null, null, null,
+        )?.use { if (it.moveToFirst()) it.getInt(0) != 0 else null }
+    }
+
+    override fun canWriteCalendars(): Boolean =
+        ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_CALENDAR) ==
+            PackageManager.PERMISSION_GRANTED
+
     override fun createManagedCalendar(displayName: String, color: Int, type: SpecialDateType): Long {
         val name = displayName.trim().ifEmpty { Fallbacks.UNNAMED_CALENDAR }
         val values = ContentValues().apply {

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarMapper.kt

@@ -31,5 +31,10 @@ internal fun ColumnReader.toCalendarSource(): CalendarSource {
         isManaged = isLocal &&
             getString(CalendarProjection.IDX_MANAGED_MARKER)
                 ?.startsWith(CalendarProjection.MANAGED_MARKER_PREFIX) == true,
+        // A provider that leaves the column NULL is treated as syncing — the
+        // harmless default, since this flag only ever holds the one-shot
+        // visibility migration back from switching a calendar on.
+        syncsEvents = isNull(CalendarProjection.IDX_SYNC_EVENTS) ||
+            getInt(CalendarProjection.IDX_SYNC_EVENTS) != 0,
     )
 }

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepository.kt

@@ -38,6 +38,20 @@ interface CalendarRepository {
     /** Permanently delete a local calendar the app owns, with all its events. */
     suspend fun deleteCalendar(id: Long)
 
+    /**
+     * Show or hide [ids] device-wide (`Calendars.VISIBLE`), which is also what
+     * turns the provider's reminder scheduling for them on or off — see
+     * [CalendarDataSource.setCalendarVisible]. Each calendar is written on its
+     * own, in order; a failure part-way leaves the earlier writes standing (the
+     * observer reports whatever actually landed).
+     *
+     * Without `WRITE_CALENDAR` the choice is kept app-side instead (see
+     * [de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs.pendingDisabledCalendarIds]),
+     * where it filters events and reminders just the same until it can be
+     * written.
+     */
+    suspend fun setCalendarsVisible(ids: Collection<Long>, visible: Boolean)
+
     /**
      * Every event of the writable local calendars, ready to serialise into a
      * whole-calendar `.ics` backup (see [CalendarDataSource.exportableEvents]).

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt

@@ -20,7 +20,10 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.onStart
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import kotlinx.coroutines.withContext
+import java.util.concurrent.atomic.AtomicLong
 import kotlin.time.Instant
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -47,52 +50,115 @@ class CalendarRepositoryImpl @Inject constructor(
         extraBufferCapacity = 1,
     )
 
+    /**
+     * Bumped on every provider notification, so one tick's calendar read can be
+     * shared by everything that needs it (see [calendarsSnapshot]).
+     */
+    private val generation = AtomicLong(0L)
+
     init {
-        dataSource.registerChangeListener { ticks.tryEmit(Unit) }
+        dataSource.registerChangeListener {
+            generation.incrementAndGet()
+            ticks.tryEmit(Unit)
+        }
     }
 
+    // A switch-off the app hasn't been allowed to write yet is folded into the
+    // flag itself, so every consumer — the Settings switch, the filter sheet,
+    // the form and import pickers, the widgets — reads one visibility and can't
+    // disagree with what the user just tapped. The reconciler reads the data
+    // source directly, because it needs the provider's own answer.
     override fun calendars(): Flow<List<CalendarSource>> =
-        ticks
-            .onStart { emit(Unit) }
-            .reQuery { dataSource.calendars() }
-            .flowOn(io)
+        combine(
+            ticks.onStart { emit(Unit) }.reQuery { calendarsSnapshot() },
+            prefs.pendingDisabledCalendarIds,
+        ) { calendars, pendingDisabled ->
+            if (pendingDisabled.isEmpty()) calendars
+            else calendars.map {
+                if (it.id in pendingDisabled) it.copy(isVisibleInSystem = false) else it
+            }
+        }.flowOn(io)
 
-    // Instances are filtered by the app-side hidden ∪ disabled calendar sets
-    // (M3): an event is dropped whenever the user has hidden *or* disabled its
-    // calendar. Re-runs when the provider ticks *or* either set changes —
-    // toggling a calendar in the filter sheet or the calendar manager updates
-    // every view immediately. [calendars] stays unfiltered so those screens can
-    // list and re-enable hidden/disabled calendars.
+    // Instances are filtered by the system's per-calendar VISIBLE flag ∪ the
+    // switch-offs still waiting to be written to it ∪ the app-side hidden set:
+    // an event is dropped when the user switched its calendar off in Settings →
+    // Calendars (which also stops the provider scheduling its reminders) *or*
+    // hid it in the filter sheet. Re-runs when the provider ticks — writing
+    // VISIBLE notifies, so switching a calendar updates every view — or when
+    // either set changes. [calendars] stays unfiltered so those screens can list
+    // and re-enable invisible calendars.
     override fun instances(range: ClosedRange<Instant>): Flow<List<EventInstance>> =
         combine(
             ticks
                 .onStart { emit(Unit) }
                 .reQuery {
-                    dataSource.instances(
-                        beginMillis = range.start.toEpochMillis(),
-                        endMillis = range.endInclusive.toEpochMillis(),
+                    // Both reads in one pass, so a list of instances is never
+                    // filtered against a visibility snapshot from another tick.
+                    QueriedInstances(
+                        instances = dataSource.instances(
+                            beginMillis = range.start.toEpochMillis(),
+                            endMillis = range.endInclusive.toEpochMillis(),
+                        ),
+                        invisibleCalendarIds = invisibleCalendarIds(),
                     )
                 },
             prefs.hiddenCalendarIds,
-            prefs.disabledCalendarIds,
-        ) { instances, hidden, disabled ->
-            val excluded = hidden + disabled
-            if (excluded.isEmpty()) instances
-            else instances.filterNot { it.calendarId in excluded }
+            prefs.pendingDisabledCalendarIds,
+        ) { queried, hidden, pendingDisabled ->
+            val excluded = hidden + pendingDisabled + queried.invisibleCalendarIds
+            if (excluded.isEmpty()) queried.instances
+            else queried.instances.filterNot { it.calendarId in excluded }
         }
-            // hidden and disabled both derive from one DataStore, so toggling
-            // either makes both re-emit and combine briefly surfaces the same
-            // list twice — collapse the duplicate so views don't re-render for it.
+            // Any DataStore edit re-emits the hidden set even when it is
+            // unchanged (e.g. writing the last-used calendar), which would
+            // re-surface an identical list — collapse those so views don't
+            // re-render for them.
             .distinctUntilChanged()
             .flowOn(io)
 
+    /** One instances query plus the visibility it must be filtered against. */
+    private data class QueriedInstances(
+        val instances: List<EventInstance>,
+        val invisibleCalendarIds: Set<Long>,
+    )
+
+    /** Calendars switched off at system level — hidden, and never reminded about. */
+    private suspend fun invisibleCalendarIds(): Set<Long> = calendarsSnapshot()
+        .filterNot { it.isVisibleInSystem }
+        .mapTo(mutableSetOf()) { it.id }
+
+    private val calendarsLock = Mutex()
+    private var cachedGeneration = -1L
+    private var cachedCalendars: List<CalendarSource> = emptyList()
+
+    /**
+     * The calendar list for the current tick, queried once and shared. Every
+     * open view collects [calendars] *and* filters its instances by visibility,
+     * which used to cost one full `Calendars` query each per tick. Reusing a
+     * single read also keeps them consistent: within a tick, what a screen lists
+     * and what its events are filtered against can't come from two snapshots.
+     *
+     * An empty result is never cached — it is what a read without the calendar
+     * permission returns, and the grant itself doesn't notify the provider.
+     */
+    private suspend fun calendarsSnapshot(): List<CalendarSource> = calendarsLock.withLock {
+        val current = generation.get()
+        if (current != cachedGeneration || cachedCalendars.isEmpty()) {
+            cachedCalendars = dataSource.calendars()
+            cachedGeneration = current
+        }
+        cachedCalendars
+    }
+
     override suspend fun eventDetail(eventId: Long): EventDetail = withContext(io) {
         dataSource.eventDetail(eventId) ?: throw NoSuchEventException(eventId)
     }
 
     override suspend fun searchEvents(query: String): List<EventInstance> = withContext(io) {
         if (query.isBlank()) return@withContext emptyList()
-        val excluded = prefs.hiddenCalendarIds.first() + prefs.disabledCalendarIds.first()
+        val excluded = prefs.hiddenCalendarIds.first() +
+            prefs.pendingDisabledCalendarIds.first() +
+            invisibleCalendarIds()
         dataSource.searchEvents(query)
             .let { if (excluded.isEmpty()) it else it.filterNot { e -> e.calendarId in excluded } }
     }
@@ -118,6 +184,22 @@ class CalendarRepositoryImpl @Inject constructor(
     override suspend fun deleteCalendar(id: Long) =
         withContext(io) { dataSource.deleteCalendar(id) }
 
+    override suspend fun setCalendarsVisible(ids: Collection<Long>, visible: Boolean) =
+        withContext(io) {
+            if (dataSource.canWriteCalendars()) {
+                ids.forEach { dataSource.setCalendarVisible(it, visible) }
+                // Nothing of ours is left waiting for the provider once the
+                // write lands (and switching one back on retires its entry).
+                prefs.removePendingDisabledCalendarIds(ids)
+            } else if (visible) {
+                prefs.removePendingDisabledCalendarIds(ids)
+            } else {
+                // Read-only permission: the switch still works, app-side, and
+                // the reconciler flushes it if WRITE_CALENDAR ever arrives.
+                prefs.addPendingDisabledCalendarIds(ids)
+            }
+        }
+
     override suspend fun exportEvents(calendarIds: Set<Long>?) =
         withContext(io) { dataSource.exportableEvents(calendarIds) }
 

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarVisibilityReconciler.kt

@@ -0,0 +1,106 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import android.Manifest
+import android.content.Context
+import android.content.pm.PackageManager
+import android.util.Log
+import androidx.core.content.ContextCompat
+import dagger.hilt.EntryPoint
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import de.jeanlucmakiola.calendula.data.di.IoDispatcher
+import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
+import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.calendarVisibilityPlan
+import de.jeanlucmakiola.calendula.domain.hasSystemHiddenCalendars
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.withContext
+import kotlin.coroutines.cancellation.CancellationException
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Keeps the app's pending "switched off" set (see
+ * [CalendarPrefs.pendingDisabledCalendarIds]) and the system's
+ * `Calendars.VISIBLE` in step — the fold-in of the retired app-local visibility
+ * model (#75), and the standing drain for switch-offs made without
+ * `WRITE_CALENDAR`.
+ *
+ * Runs on every launch, and again the moment the permission screen grants the
+ * calendar permissions. It is a no-op whenever the pending set is empty, which
+ * is the steady state: each entry is written and dropped individually, so a run
+ * that dies part-way resumes exactly where it stopped and never re-applies a
+ * write the user has since undone by hand.
+ *
+ * The reconciliation only hides (see [calendarVisibilityPlan]). Calendars hidden
+ * at system level stay hidden, and the first run that sees one arms the one-time
+ * notice explaining why Calendula no longer lists their events.
+ */
+@Singleton
+class CalendarVisibilityReconciler @Inject constructor(
+    @ApplicationContext private val context: Context,
+    private val dataSource: CalendarDataSource,
+    private val prefs: CalendarPrefs,
+    @IoDispatcher private val io: CoroutineDispatcher,
+) {
+
+    suspend fun run() = withContext(io) {
+        // Everything, the DataStore reads included, sits inside the guard: this
+        // runs in a bare application-scope coroutine with no exception handler,
+        // so an IOException from a damaged preferences file would otherwise take
+        // the process down on every launch.
+        try {
+            if (!hasPermission(Manifest.permission.READ_CALENDAR)) return@withContext
+            val pending = prefs.pendingDisabledCalendarIds.first()
+            val calendars = dataSource.calendars()
+            armNoticeOnce(calendars, pending)
+            if (pending.isEmpty() || !hasPermission(Manifest.permission.WRITE_CALENDAR)) {
+                return@withContext
+            }
+            val plan = calendarVisibilityPlan(calendars, pending)
+            // Already off, or gone from the device — nothing to write, so let
+            // those ids leave the pending set with the rest.
+            prefs.removePendingDisabledCalendarIds(plan.settled)
+            // One calendar per write: the provider skips its reminder-alarm
+            // reschedule for anything but a single-id update (see
+            // [CalendarDataSource.setCalendarVisible]). Dropping each id as it
+            // lands keeps a part-applied run resumable.
+            for (id in plan.hide) {
+                dataSource.setCalendarVisible(id, false)
+                prefs.removePendingDisabledCalendarIds(setOf(id))
+            }
+        } catch (e: CancellationException) {
+            throw e
+        } catch (e: Exception) {
+            Log.w(TAG, "Calendar visibility reconcile failed; will retry", e)
+        }
+    }
+
+    /**
+     * Arm the one-time notice if the device holds a calendar switched off
+     * outside Calendula. Evaluated once, on the first run that can read the
+     * calendars at all; the answer — including "nothing to say" — is stored, so
+     * the notice can't resurface later, when the same state would no longer be
+     * news to the user.
+     */
+    private suspend fun armNoticeOnce(calendars: List<CalendarSource>, pending: Set<Long>) {
+        if (prefs.visibilityNoticePending.first() != null) return
+        prefs.setVisibilityNoticePending(hasSystemHiddenCalendars(calendars, pending))
+    }
+
+    private fun hasPermission(permission: String): Boolean =
+        ContextCompat.checkSelfPermission(context, permission) == PackageManager.PERMISSION_GRANTED
+
+    /** Lets non-injectable entry points (the Application) reach the reconciler. */
+    @EntryPoint
+    @InstallIn(SingletonComponent::class)
+    interface Deps {
+        fun calendarVisibilityReconciler(): CalendarVisibilityReconciler
+    }
+
+    private companion object {
+        const val TAG = "CalendarVisibility"
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/Projections.kt

@@ -19,6 +19,7 @@ internal object CalendarProjection {
         // uses to recognise its own managed calendars, independent of any
         // stored preference id (which a backup restore / data wipe can lose).
         MANAGED_MARKER_COLUMN,
+        CalendarContract.Calendars.SYNC_EVENTS,
     )
 
     const val DESCRIPTION_COLUMN: String = CalendarContract.Calendars.CAL_SYNC1
@@ -36,6 +37,7 @@ internal object CalendarProjection {
     const val IDX_ACCESS_LEVEL = 6
     const val IDX_DESCRIPTION = 7
     const val IDX_MANAGED_MARKER = 8
+    const val IDX_SYNC_EVENTS = 9
 }
 
 internal object InstanceProjection {

app/src/main/java/de/jeanlucmakiola/calendula/data/prefs/CalendarPrefs.kt

@@ -1,7 +1,9 @@
 package de.jeanlucmakiola.calendula.data.prefs
 
 import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.MutablePreferences
 import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.booleanPreferencesKey
 import androidx.datastore.preferences.core.edit
 import androidx.datastore.preferences.core.longPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
@@ -11,8 +13,12 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 /**
- * App-side preference for "calendars the user has hidden in this app",
- * separate from the system's per-calendar VISIBLE flag.
+ * App-side calendar preferences. [hiddenCalendarIds] is the drawer's filter
+ * sheet — a purely in-app declutter that deliberately does *not* suppress
+ * reminders. Switching a calendar off entirely is the system's
+ * `Calendars.VISIBLE` flag, written straight to the provider (#75);
+ * [pendingDisabledCalendarIds] only holds those switch-offs the app has not been
+ * allowed to write yet.
  *
  * Persisted as a comma-separated string of Long ids; non-numeric tokens are
  * silently dropped (defensive — see CalendarPrefsTest).
@@ -23,45 +29,58 @@ class CalendarPrefs @Inject constructor(
 ) {
 
     val hiddenCalendarIds: Flow<Set<Long>> = store.data.map { prefs ->
-        prefs[HIDDEN_IDS_KEY].orEmpty()
-            .split(',')
-            .mapNotNull { it.trim().toLongOrNull() }
-            .toSet()
+        prefs[HIDDEN_IDS_KEY].parseIds()
     }
 
     suspend fun setHiddenCalendarIds(ids: Set<Long>) {
+        store.edit { prefs -> prefs.writeIds(HIDDEN_IDS_KEY, ids) }
+    }
+
+    /**
+     * Calendars switched off in Settings → Calendars that the provider does not
+     * know about yet. That switch writes the system's `Calendars.VISIBLE` (#75),
+     * which needs `WRITE_CALENDAR` — a user who granted read-only keeps their
+     * choice here instead, and so does everyone upgrading from the retired
+     * app-local model, whose set is read straight back out of the same key.
+     *
+     * Honoured as a display and reminder filter for as long as it is non-empty,
+     * so an un-flushable switch still does what the user asked. Not a second
+     * visibility model: `CalendarVisibilityReconciler` drains it into the
+     * provider entry by entry the moment the app may write, and nothing ever
+     * adds to it while it may.
+     */
+    val pendingDisabledCalendarIds: Flow<Set<Long>> = store.data.map { prefs ->
+        prefs[DISABLED_IDS_KEY].parseIds()
+    }
+
+    suspend fun addPendingDisabledCalendarIds(ids: Collection<Long>) =
+        editPendingDisabled { it + ids }
+
+    /**
+     * Drop [ids] from the pending set — one id at a time as the reconciler
+     * flushes it, so a run that fails part-way never re-applies what already
+     * landed (and can't undo a switch the user has since flipped by hand).
+     */
+    suspend fun removePendingDisabledCalendarIds(ids: Collection<Long>) =
+        editPendingDisabled { it - ids.toSet() }
+
+    private suspend fun editPendingDisabled(transform: (Set<Long>) -> Set<Long>) {
         store.edit { prefs ->
-            if (ids.isEmpty()) {
-                prefs.remove(HIDDEN_IDS_KEY)
-            } else {
-                prefs[HIDDEN_IDS_KEY] = ids.sorted().joinToString(",")
-            }
+            prefs.writeIds(DISABLED_IDS_KEY, transform(prefs[DISABLED_IDS_KEY].parseIds()))
         }
     }
 
     /**
-     * App-side preference for "calendars the user has disabled in this app" — a
-     * heavier level than [hiddenCalendarIds]. A disabled calendar is removed from
-     * every surface (drawer filter, event-form picker, import picker) and its
-     * events never appear; it stays listed only in Settings → Calendars so it can
-     * be re-enabled. Stored exactly like the hidden set; never touches the
-     * system's VISIBLE/SYNC_EVENTS flags, so other calendar apps are unaffected.
+     * Whether the one-time "visibility follows this device" notice is still
+     * owed. Null until the reconciler has evaluated it (which needs the calendar
+     * permission), false once it has been shown or was never needed.
      */
-    val disabledCalendarIds: Flow<Set<Long>> = store.data.map { prefs ->
-        prefs[DISABLED_IDS_KEY].orEmpty()
-            .split(',')
-            .mapNotNull { it.trim().toLongOrNull() }
-            .toSet()
+    val visibilityNoticePending: Flow<Boolean?> = store.data.map { prefs ->
+        prefs[VISIBILITY_NOTICE_KEY]
     }
 
-    suspend fun setDisabledCalendarIds(ids: Set<Long>) {
-        store.edit { prefs ->
-            if (ids.isEmpty()) {
-                prefs.remove(DISABLED_IDS_KEY)
-            } else {
-                prefs[DISABLED_IDS_KEY] = ids.sorted().joinToString(",")
-            }
-        }
+    suspend fun setVisibilityNoticePending(pending: Boolean) {
+        store.edit { prefs -> prefs[VISIBILITY_NOTICE_KEY] = pending }
     }
 
     /**
@@ -79,6 +98,16 @@ class CalendarPrefs @Inject constructor(
     companion object {
         internal val HIDDEN_IDS_KEY = stringPreferencesKey("hidden_calendar_ids")
         internal val DISABLED_IDS_KEY = stringPreferencesKey("disabled_calendar_ids")
+        internal val VISIBILITY_NOTICE_KEY = booleanPreferencesKey("visibility_notice_pending")
         internal val LAST_USED_CALENDAR_KEY = longPreferencesKey("last_used_calendar_id")
     }
 }
+
+private fun String?.parseIds(): Set<Long> = orEmpty()
+    .split(',')
+    .mapNotNull { it.trim().toLongOrNull() }
+    .toSet()
+
+private fun MutablePreferences.writeIds(key: Preferences.Key<String>, ids: Set<Long>) {
+    if (ids.isEmpty()) remove(key) else set(key, ids.sorted().joinToString(","))
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/EventReminderReceiver.kt

@@ -8,7 +8,6 @@ import android.content.pm.PackageManager
 import android.provider.CalendarContract
 import androidx.core.content.ContextCompat
 import dagger.hilt.android.AndroidEntryPoint
-import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -17,29 +16,6 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
 import javax.inject.Inject
 
-/**
- * True when [this] alert belongs to a calendar the user disabled in-app, so its
- * reminder must be suppressed (mirroring the event filtering in
- * CalendarRepositoryImpl). Alerts whose calendar is unknown (id 0L — e.g. a
- * pre-upgrade snooze PendingIntent minted before EXTRA_CALENDAR_ID existed) are
- * never treated as disabled. This is the one predicate the disabled-calendar
- * gate is built from: [postableAlerts] here and the choke point in
- * [ReminderNotifier.post] both use it.
- */
-internal fun ReminderAlert.isForDisabledCalendar(disabledCalendarIds: Set<Long>): Boolean =
-    calendarId != 0L && calendarId in disabledCalendarIds
-
-/**
- * The due alerts that should actually surface as notifications: everything
- * except alerts whose calendar the user has disabled in-app. The caller still
- * marks the full due set fired, so suppressed alerts are not re-broadcast by the
- * provider.
- */
-internal fun postableAlerts(
-    due: List<ReminderAlert>,
-    disabledCalendarIds: Set<Long>,
-): List<ReminderAlert> = due.filterNot { it.isForDisabledCalendar(disabledCalendarIds) }
-
 /**
  * Becomes the app that turns the calendar provider's reminder alarms into
  * visible notifications (the Etar model — the provider broadcasts
@@ -49,6 +25,12 @@ internal fun postableAlerts(
  * we query every still-scheduled, due `CalendarAlerts` row ourselves, post
  * them, and mark them fired. Posting happens before marking — a crash in
  * between re-posts silently (same tag) rather than losing the reminder.
+ *
+ * There is no per-calendar filtering here: a calendar switched off in
+ * Settings → Calendars has `Calendars.VISIBLE = 0`, and the provider creates no
+ * alert rows for it in the first place (#75). The one case that flag can't
+ * cover — a read-only install, which keeps its switches app-side — is gated in
+ * [ReminderNotifier.post], where the snoozed re-show passes too.
  */
 @AndroidEntryPoint
 class EventReminderReceiver : BroadcastReceiver() {
@@ -56,8 +38,6 @@ class EventReminderReceiver : BroadcastReceiver() {
     @Inject lateinit var alertStore: ReminderAlertStore
     @Inject lateinit var notifier: ReminderNotifier
     @Inject lateinit var settingsPrefs: SettingsPrefs
-    @Inject lateinit var calendarPrefs: CalendarPrefs
-    @Inject lateinit var suppressedStore: SuppressedReminderStore
 
     override fun onReceive(context: Context, intent: Intent) {
         if (intent.action != CalendarContract.ACTION_EVENT_REMINDER) return
@@ -72,17 +52,8 @@ class EventReminderReceiver : BroadcastReceiver() {
                 if (settingsPrefs.remindersEnabled.first()) {
                     val now = System.currentTimeMillis()
                     val due = alertStore.dueAlerts(now)
-                    val disabled = calendarPrefs.disabledCalendarIds.first()
-                    val postable = postableAlerts(due, disabled)
-                    // Suppress reminders for disabled calendars, but still mark
-                    // every due alert fired so the provider stops re-broadcasting
-                    // the suppressed ones. Stash those suppressed alerts so
-                    // re-enabling their calendar can recover them (they would
-                    // otherwise stay STATE_FIRED forever with no re-scan).
-                    postable.forEach { notifier.post(it) }
+                    due.forEach { notifier.post(it) }
                     alertStore.markFired(due.map { it.alertId }, now)
-                    suppressedStore.stash(due - postable.toSet(), now)
-                    suppressedStore.purgeExpired(now)
                 }
             } finally {
                 pendingResult.finish()

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/ReminderActionReceiver.kt

@@ -23,7 +23,9 @@ import javax.inject.Inject
  * - **Snooze** cancels the notification and schedules an exact alarm to re-show
  *   it after the user's snooze delay.
  * - **Show** (the alarm) re-posts the same notification, so the user can snooze
- *   or dismiss it again.
+ *   or dismiss it again — unless the calendar was switched off during the
+ *   snooze, which [ReminderNotifier.post] catches (this alarm is ours, so no
+ *   provider alert row stands between it and the notification).
  */
 @AndroidEntryPoint
 class ReminderActionReceiver : BroadcastReceiver() {

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/ReminderNotifier.kt

@@ -14,6 +14,7 @@ import androidx.core.content.ContextCompat
 import dagger.hilt.android.qualifiers.ApplicationContext
 import de.jeanlucmakiola.calendula.MainActivity
 import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.data.calendar.CalendarDataSource
 import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.data.prefs.is24Hour
@@ -39,6 +40,7 @@ class ReminderNotifier @Inject constructor(
     @ApplicationContext private val context: Context,
     private val settingsPrefs: SettingsPrefs,
     private val calendarPrefs: CalendarPrefs,
+    private val calendarDataSource: CalendarDataSource,
 ) {
 
     /** False when the user declined `POST_NOTIFICATIONS` or muted the app. */
@@ -49,12 +51,21 @@ class ReminderNotifier @Inject constructor(
         return granted && NotificationManagerCompat.from(context).areNotificationsEnabled()
     }
 
+    /**
+     * The single choke point for "this calendar is switched off". The provider
+     * side needs no help — with `VISIBLE = 0` it creates no alert rows at all —
+     * but two paths reach [post] without one: a snooze we re-show from our own
+     * exact alarm, scheduled before the calendar was switched off, and a
+     * read-only install whose switch lives app-side ([CalendarPrefs]) because it
+     * may not write the flag. Both are covered here rather than in either
+     * receiver.
+     */
+    private suspend fun isSilenced(calendarId: Long): Boolean =
+        calendarId in calendarPrefs.pendingDisabledCalendarIds.first() ||
+            calendarDataSource.isCalendarVisible(calendarId) == false
+
     suspend fun post(alert: ReminderAlert) {
-        // The single choke point for the disabled-calendar gate: it covers both
-        // the provider broadcast (EventReminderReceiver) and a snoozed re-show
-        // (ReminderActionReceiver), so a calendar disabled after a snooze no
-        // longer notifies — without either receiver duplicating the check.
-        if (alert.isForDisabledCalendar(calendarPrefs.disabledCalendarIds.first())) return
+        if (isSilenced(alert.calendarId)) return
         ensureChannel()
         val title = alert.title.ifBlank { context.getString(R.string.event_untitled) }
         val is24Hour = settingsPrefs.timeFormat.first()

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/SuppressedReminderStore.kt

@@ -1,130 +0,0 @@
-package de.jeanlucmakiola.calendula.data.reminders
-
-import androidx.datastore.core.DataStore
-import androidx.datastore.preferences.core.MutablePreferences
-import androidx.datastore.preferences.core.Preferences
-import androidx.datastore.preferences.core.edit
-import androidx.datastore.preferences.core.stringSetPreferencesKey
-import java.util.Base64
-import javax.inject.Inject
-import javax.inject.Singleton
-
-/**
- * Still relevant while the event has not ended: a reminder for an event that is
- * already over is pointless to re-surface. Falls back to the begin time when the
- * end is unknown (0L). Used both to decide what to re-post and to purge the stash.
- */
-internal fun ReminderAlert.isRelevantAt(nowMillis: Long): Boolean =
-    (endMillis.takeIf { it > 0L } ?: beginMillis) >= nowMillis
-
-/**
- * Local stash of reminder alerts that fired while their calendar was disabled
- * in-app. [EventReminderReceiver] marks every due alert `STATE_FIRED` regardless
- * (so the provider stops re-broadcasting the suppressed ones), which would
- * otherwise lose those reminders forever — there is no re-scan. Stashing lets
- * [de.jeanlucmakiola.calendula.ui.calendars.CalendarsViewModel] re-post them if
- * the user re-enables the calendar before the event is over.
- *
- * Persisted in the shared preferences DataStore as a set of self-describing
- * strings (one per alert); the stash never reaches a screen, so there is no
- * domain model. Entries whose event has already ended are dropped on the next
- * stash/recover/purge, so the stash only ever holds a handful of pending alerts.
- */
-@Singleton
-class SuppressedReminderStore @Inject constructor(
-    private val store: DataStore<Preferences>,
-) {
-
-    /** Add [alerts] to the stash, replacing any existing entry with the same id. */
-    suspend fun stash(alerts: List<ReminderAlert>, nowMillis: Long) {
-        if (alerts.isEmpty()) return
-        store.edit { prefs ->
-            val byId = decodeAll(prefs).associateByTo(mutableMapOf()) { it.alertId }
-            alerts.forEach { byId[it.alertId] = it }
-            prefs.putStash(byId.values.filter { it.isRelevantAt(nowMillis) })
-        }
-    }
-
-    /**
-     * Remove and return the still-relevant stashed alerts belonging to any of
-     * [calendarIds]; drops expired entries for every calendar in passing.
-     */
-    suspend fun recoverFor(calendarIds: Set<Long>, nowMillis: Long): List<ReminderAlert> {
-        val recovered = mutableListOf<ReminderAlert>()
-        store.edit { prefs ->
-            val kept = decodeAll(prefs).filter { alert ->
-                when {
-                    !alert.isRelevantAt(nowMillis) -> false // expired: drop
-                    alert.calendarId in calendarIds -> { recovered += alert; false }
-                    else -> true
-                }
-            }
-            prefs.putStash(kept)
-        }
-        return recovered
-    }
-
-    /** Drop entries whose event has already ended — cheap opportunistic cleanup. */
-    suspend fun purgeExpired(nowMillis: Long) {
-        store.edit { prefs ->
-            prefs.putStash(decodeAll(prefs).filter { it.isRelevantAt(nowMillis) })
-        }
-    }
-
-    private fun decodeAll(prefs: Preferences): List<ReminderAlert> =
-        prefs[KEY].orEmpty().mapNotNull { decodeStashEntry(it) }
-
-    private fun MutablePreferences.putStash(alerts: List<ReminderAlert>) {
-        val encoded = alerts.map { encodeStashEntry(it) }.toSet()
-        if (encoded.isEmpty()) remove(KEY) else set(KEY, encoded)
-    }
-
-    private companion object {
-        val KEY = stringSetPreferencesKey("suppressed_reminders")
-    }
-}
-
-// One stash entry as a delimited string. The '|' separator is safe because every
-// free-text field is Base64-encoded first (that alphabet never contains '|'), and
-// a null location is stored as a distinct sentinel that Base64 also never yields.
-private const val FIELD_SEP = "|"
-private const val NULL_LOCATION = "-"
-
-internal fun encodeStashEntry(alert: ReminderAlert): String = listOf(
-    alert.alertId.toString(),
-    alert.eventId.toString(),
-    alert.calendarId.toString(),
-    alert.beginMillis.toString(),
-    alert.endMillis.toString(),
-    if (alert.isAllDay) "1" else "0",
-    alert.title.toBase64(),
-    alert.location?.toBase64() ?: NULL_LOCATION,
-).joinToString(FIELD_SEP)
-
-/** Reverse of [encodeStashEntry]; returns null for a malformed entry (dropped). */
-internal fun decodeStashEntry(raw: String): ReminderAlert? {
-    val parts = raw.split(FIELD_SEP)
-    if (parts.size != 8) return null
-    return try {
-        ReminderAlert(
-            alertId = parts[0].toLong(),
-            eventId = parts[1].toLong(),
-            calendarId = parts[2].toLong(),
-            beginMillis = parts[3].toLong(),
-            endMillis = parts[4].toLong(),
-            title = parts[6].fromBase64(),
-            location = parts[7].takeIf { it != NULL_LOCATION }?.fromBase64(),
-            isAllDay = parts[5] == "1",
-        )
-    } catch (e: NumberFormatException) {
-        null
-    } catch (e: IllegalArgumentException) { // bad Base64
-        null
-    }
-}
-
-private fun String.toBase64(): String =
-    Base64.getEncoder().encodeToString(toByteArray(Charsets.UTF_8))
-
-private fun String.fromBase64(): String =
-    String(Base64.getDecoder().decode(this), Charsets.UTF_8)

app/src/main/java/de/jeanlucmakiola/calendula/domain/CalendarVisibilityPlan.kt

@@ -0,0 +1,58 @@
+package de.jeanlucmakiola.calendula.domain
+
+/**
+ * The `Calendars.VISIBLE` writes that flush the app's pending "switched off"
+ * set into the provider, plus the ids that need no write at all.
+ */
+data class CalendarVisibilityPlan(
+    val hide: Set<Long> = emptySet(),
+    val settled: Set<Long> = emptySet(),
+) {
+    val isEmpty: Boolean get() = hide.isEmpty() && settled.isEmpty()
+}
+
+/**
+ * Reconcile [pendingDisabledIds] — calendars switched off in Settings →
+ * Calendars while the app could not write `Calendars.VISIBLE`, plus whatever
+ * the retired app-local visibility model left behind (#75) — against the
+ * calendars actually on the device.
+ *
+ * The plan only ever *hides*. Switching a calendar off is intent the user
+ * expressed in Calendula, so carrying it into the provider is fair. The other
+ * direction is deliberately absent: a calendar hidden at system level was hidden
+ * somewhere else (another calendar app, the account's own settings), and
+ * switching it back on would un-hide it there too *and* start firing reminders
+ * nobody asked for. Calendula follows that flag instead and explains itself once
+ * (see [hasSystemHiddenCalendars]).
+ *
+ * [CalendarVisibilityPlan.settled] carries the ids that need no write — already
+ * hidden, or gone from the device. They leave the pending set exactly as a
+ * successful write would.
+ */
+fun calendarVisibilityPlan(
+    calendars: List<CalendarSource>,
+    pendingDisabledIds: Set<Long>,
+): CalendarVisibilityPlan {
+    val byId = calendars.associateBy { it.id }
+    val hide = mutableSetOf<Long>()
+    val settled = mutableSetOf<Long>()
+    for (id in pendingDisabledIds) {
+        val calendar = byId[id]
+        // No row means the calendar is gone; already invisible means someone
+        // (us, on an earlier run) got there first. Either way: nothing to write.
+        if (calendar != null && calendar.isVisibleInSystem) hide += id else settled += id
+    }
+    return CalendarVisibilityPlan(hide = hide, settled = settled)
+}
+
+/**
+ * Whether any calendar is switched off at system level without Calendula having
+ * asked for it. Those calendars showed their events before the app adopted
+ * `Calendars.VISIBLE` as its one visibility model and no longer do, which is
+ * what the one-time notice explains — the alternative, switching them on, would
+ * reach into every other calendar app on the device.
+ */
+fun hasSystemHiddenCalendars(
+    calendars: List<CalendarSource>,
+    pendingDisabledIds: Set<Long>,
+): Boolean = calendars.any { !it.isVisibleInSystem && it.id !in pendingDisabledIds }

app/src/main/java/de/jeanlucmakiola/calendula/domain/Models.kt

@@ -8,6 +8,13 @@ data class CalendarSource(
     val accountName: String,
     val accountType: String,
     val color: Int,
+    /**
+     * The system's per-calendar `Calendars.VISIBLE` flag — the single visibility
+     * model: it decides both what Calendula shows and whether the provider
+     * schedules this calendar's reminder alarms at all (#75). Settings →
+     * Calendars writes it; the drawer's filter sheet is a separate, purely
+     * in-app declutter that leaves reminders alone.
+     */
     val isVisibleInSystem: Boolean,
     /**
      * Whether events in this calendar can be created/edited/deleted
@@ -34,6 +41,15 @@ data class CalendarSource(
      * even after a backup restore clears the app's stored ids.
      */
     val isManaged: Boolean = false,
+    /**
+     * Whether the provider keeps this calendar's events on the device
+     * (`Calendars.SYNC_EVENTS`). Independent of [isVisibleInSystem]. For a
+     * synced account it means the events aren't stored locally at all, so the
+     * calendar reads as permanently empty; a device-local calendar another app
+     * created can hold events with the flag off, so it says nothing there.
+     * Read for the "not synced" row label (#76).
+     */
+    val syncsEvents: Boolean = true,
 )
 
 data class EventInstance(

app/src/main/java/de/jeanlucmakiola/calendula/ui/RootScreen.kt

@@ -21,6 +21,8 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import de.jeanlucmakiola.calendula.data.contacts.SpecialDatesScheduler
 import de.jeanlucmakiola.calendula.data.contacts.hasContactsPermission
+import de.jeanlucmakiola.calendula.ui.calendars.CalendarVisibilityNoticeDialog
+import de.jeanlucmakiola.calendula.ui.calendars.CalendarVisibilityNoticeViewModel
 import de.jeanlucmakiola.calendula.ui.permission.PermissionScreen
 import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingScreen
 import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingViewModel
@@ -78,6 +80,13 @@ fun RootScreen(
             // frame instead of flashing the wrong screen.
             val reminderOnboarding: ReminderOnboardingViewModel = hiltViewModel()
             val onboardingDone by reminderOnboarding.onboardingDone.collectAsStateWithLifecycle()
+            // One-time explainer for the switch to the device's own calendar
+            // visibility (#75); armed by the reconciler, shown over the app.
+            val visibilityNotice: CalendarVisibilityNoticeViewModel = hiltViewModel()
+            val noticePending by visibilityNotice.pending.collectAsStateWithLifecycle()
+            if (onboardingDone == true && noticePending) {
+                CalendarVisibilityNoticeDialog(onDismiss = visibilityNotice::dismiss)
+            }
             Crossfade(targetState = onboardingDone, animationSpec = gateSpec, label = "onboardingGate") { done ->
                 when (done) {
                     true -> CalendarHost(

app/src/main/java/de/jeanlucmakiola/calendula/ui/calendars/CalendarVisibilityNotice.kt

@@ -0,0 +1,62 @@
+package de.jeanlucmakiola.calendula.ui.calendars
+
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.VisibilityOff
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Icon
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+/**
+ * The one-time notice that Calendula now follows the device's per-calendar
+ * visibility (#75). Armed by `CalendarVisibilityReconciler` on the first launch
+ * that finds a calendar switched off outside the app — those used to show their
+ * events here and no longer do, and the app deliberately does not switch them
+ * back on, because that would un-hide them in every other calendar app too.
+ */
+@HiltViewModel
+class CalendarVisibilityNoticeViewModel @Inject constructor(
+    private val prefs: CalendarPrefs,
+) : ViewModel() {
+
+    val pending: StateFlow<Boolean> = prefs.visibilityNoticePending
+        .map { it == true }
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5_000L),
+            initialValue = false,
+        )
+
+    fun dismiss() {
+        viewModelScope.launch { prefs.setVisibilityNoticePending(false) }
+    }
+}
+
+/** Plain informational dialog — one acknowledgement, nothing to decide. */
+@Composable
+fun CalendarVisibilityNoticeDialog(onDismiss: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        icon = { Icon(Icons.Default.VisibilityOff, contentDescription = null) },
+        title = { Text(stringResource(R.string.calendars_visibility_notice_title)) },
+        text = { Text(stringResource(R.string.calendars_visibility_notice_message)) },
+        confirmButton = {
+            TextButton(onClick = onDismiss) {
+                Text(stringResource(R.string.dialog_ok))
+            }
+        },
+    )
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/calendars/CalendarsScreen.kt

@@ -139,7 +139,6 @@ fun CalendarsScreen(
     viewModel: CalendarsViewModel = hiltViewModel(),
 ) {
     val calendars by viewModel.calendars.collectAsStateWithLifecycle()
-    val disabledIds by viewModel.disabledCalendarIds.collectAsStateWithLifecycle()
     val error by viewModel.error.collectAsStateWithLifecycle()
     val backupResult by viewModel.backupResult.collectAsStateWithLifecycle()
     val autoBackup by viewModel.autoBackup.collectAsStateWithLifecycle()
@@ -177,7 +176,6 @@ fun CalendarsScreen(
         CalendarsList(
             local = calendars.filter { it.isLocal },
             synced = calendars.filterNot { it.isLocal },
-            disabledIds = disabledIds,
             error = error,
             onConsumeError = viewModel::consumeError,
             backupResult = backupResult,
@@ -191,8 +189,8 @@ fun CalendarsScreen(
             onBack = onBack,
             onAdd = { editorSession++; editorId = NEW_CALENDAR_ID },
             onEdit = { calendar -> editorSession++; editorId = calendar.id },
-            onSetDisabled = viewModel::setDisabled,
-            onSetAccountDisabled = viewModel::setAccountDisabled,
+            onSetVisible = viewModel::setCalendarVisible,
+            onSetAccountVisible = viewModel::setAccountVisible,
         )
     }
 }
@@ -201,7 +199,6 @@ fun CalendarsScreen(
 private fun CalendarsList(
     local: List<CalendarSource>,
     synced: List<CalendarSource>,
-    disabledIds: Set<Long>,
     error: Boolean,
     onConsumeError: () -> Unit,
     backupResult: BackupResult?,
@@ -215,8 +212,8 @@ private fun CalendarsList(
     onBack: () -> Unit,
     onAdd: () -> Unit,
     onEdit: (CalendarSource) -> Unit,
-    onSetDisabled: (Long, Boolean) -> Unit,
-    onSetAccountDisabled: (Collection<Long>, Boolean) -> Unit,
+    onSetVisible: (Long, Boolean) -> Unit,
+    onSetAccountVisible: (Collection<Long>, Boolean) -> Unit,
 ) {
     val context = LocalContext.current
     val snackbarHostState = remember { SnackbarHostState() }
@@ -281,12 +278,12 @@ private fun CalendarsList(
         predictiveBack = true,
     ) {
         // What the per-calendar / per-account switches below actually do.
-        HintText(stringResource(R.string.calendars_disable_hint))
+        HintText(stringResource(R.string.calendars_visibility_hint))
 
         // Local (device-only) calendars — one collapsible group. The header's
         // "+" adds a calendar; the switch enables/disables them all at once;
         // tapping a calendar row opens its editor.
-        val localDisabled = local.isNotEmpty() && local.all { it.id in disabledIds }
+        val localDisabled = local.isNotEmpty() && local.none { it.isVisibleInSystem }
         CalendarGroup(
             title = stringResource(R.string.calendars_local_header),
             expanded = localExpanded,
@@ -298,14 +295,14 @@ private fun CalendarsList(
             onManage = onAdd,
             onToggleExpand = { localExpanded = !localExpanded },
             showToggleAll = local.isNotEmpty(),
-            allEnabled = local.none { it.id in disabledIds },
-            onToggleAll = { enabled -> onSetAccountDisabled(local.map { it.id }, !enabled) },
+            allEnabled = local.all { it.isVisibleInSystem },
+            onToggleAll = { enabled -> onSetAccountVisible(local.map { it.id }, enabled) },
         ) {
             if (local.isEmpty()) {
                 HintText(stringResource(R.string.calendars_local_empty))
             } else {
                 local.forEachIndexed { index, calendar ->
-                    val disabled = calendar.id in disabledIds
+                    val disabled = !calendar.isVisibleInSystem
                     GroupedRow(
                         title = calendar.displayName,
                         summary = calendar.description,
@@ -317,7 +314,7 @@ private fun CalendarsList(
                             EnableSwitch(
                                 calendarName = calendar.displayName,
                                 enabled = !disabled,
-                                onToggle = { enabled -> onSetDisabled(calendar.id, !enabled) },
+                                onToggle = { enabled -> onSetVisible(calendar.id, enabled) },
                             )
                         },
                         onClick = { onEdit(calendar) },
@@ -415,7 +412,7 @@ private fun CalendarsList(
             .forEach { (account, cals) ->
                 val expanded = account !in collapsedAccounts
                 val accountType = cals.first().accountType
-                val accountDisabled = cals.all { it.id in disabledIds }
+                val accountDisabled = cals.none { it.isVisibleInSystem }
                 Spacer(Modifier.height(16.dp))
                 CalendarGroup(
                     title = account,
@@ -436,11 +433,11 @@ private fun CalendarsList(
                         }
                     },
                     showToggleAll = true,
-                    allEnabled = cals.none { it.id in disabledIds },
-                    onToggleAll = { enabled -> onSetAccountDisabled(cals.map { it.id }, !enabled) },
+                    allEnabled = cals.all { it.isVisibleInSystem },
+                    onToggleAll = { enabled -> onSetAccountVisible(cals.map { it.id }, enabled) },
                 ) {
                     cals.forEachIndexed { index, calendar ->
-                        val disabled = calendar.id in disabledIds
+                        val disabled = !calendar.isVisibleInSystem
                         GroupedRow(
                             title = calendar.displayName,
                             position = if (index == cals.lastIndex) Position.Bottom else Position.Middle,
@@ -451,7 +448,7 @@ private fun CalendarsList(
                                 EnableSwitch(
                                     calendarName = calendar.displayName,
                                     enabled = !disabled,
-                                    onToggle = { enabled -> onSetDisabled(calendar.id, !enabled) },
+                                    onToggle = { enabled -> onSetVisible(calendar.id, enabled) },
                                 )
                             },
                         )
@@ -698,10 +695,12 @@ private fun CalendarEditor(
 }
 
 /**
- * The per-row enable/disable control. Checked = the calendar is shown in the
- * app; unchecking disables it (events, filters and pickers all drop it) without
- * touching any provider data. Carries its own content description so the toggle
- * is self-describing to screen readers even on a dimmed row.
+ * The per-row on/off control, writing the system's `Calendars.VISIBLE`: checked
+ * = the calendar is shown, unchecked = it drops out of every surface (events,
+ * filters, pickers) and the provider stops scheduling its reminders. The flag is
+ * device-local — nothing is deleted and nothing is synced anywhere. Carries its
+ * own content description so the toggle is self-describing to screen readers
+ * even on a dimmed row.
  */
 @Composable
 private fun EnableSwitch(
@@ -709,7 +708,7 @@ private fun EnableSwitch(
     enabled: Boolean,
     onToggle: (Boolean) -> Unit,
 ) {
-    val label = stringResource(R.string.calendars_show_in_app_a11y, calendarName)
+    val label = stringResource(R.string.calendars_visibility_a11y, calendarName)
     Switch(
         checked = enabled,
         onCheckedChange = onToggle,

app/src/main/java/de/jeanlucmakiola/calendula/ui/calendars/CalendarsViewModel.kt

@@ -12,10 +12,7 @@ import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.ics.IcsExporter
 import de.jeanlucmakiola.calendula.data.prefs.BackupStatus
-import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
-import de.jeanlucmakiola.calendula.data.reminders.ReminderNotifier
-import de.jeanlucmakiola.calendula.data.reminders.SuppressedReminderStore
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.ics.IcsWriter
 import kotlinx.coroutines.CoroutineDispatcher
@@ -45,10 +42,7 @@ class CalendarsViewModel @Inject constructor(
     @ApplicationContext private val context: Context,
     private val repository: CalendarRepository,
     private val icsExporter: IcsExporter,
-    private val prefs: CalendarPrefs,
     private val settingsPrefs: SettingsPrefs,
-    private val suppressedStore: SuppressedReminderStore,
-    private val notifier: ReminderNotifier,
     @IoDispatcher private val io: CoroutineDispatcher,
 ) : ViewModel() {
 
@@ -62,20 +56,6 @@ class CalendarsViewModel @Inject constructor(
                 initialValue = emptyList(),
             )
 
-    /**
-     * Calendars the user has disabled in the app. This screen is the only
-     * surface that lists them, so it both reads the set (to dim the rows) and
-     * toggles it. Every other surface simply excludes these ids.
-     */
-    val disabledCalendarIds: StateFlow<Set<Long>> =
-        prefs.disabledCalendarIds
-            .flowOn(io)
-            .stateIn(
-                scope = viewModelScope,
-                started = SharingStarted.WhileSubscribed(5_000L),
-                initialValue = emptySet(),
-            )
-
     /** Automatic-backup settings + last-run status, for the Backup section UI. */
     val autoBackup: StateFlow<AutoBackupUiState> = combine(
         settingsPrefs.autoBackupEnabled,
@@ -140,54 +120,24 @@ class CalendarsViewModel @Inject constructor(
     }
 
     /**
-     * Enable or disable a calendar app-side. Disabling removes it from every
-     * surface but Settings → Calendars (and hides its events) without touching
-     * provider data — purely a reversible Calendula-local view choice.
+     * Switch a calendar on or off. This is the app's one visibility model: it
+     * writes the system's `Calendars.VISIBLE`, so the calendar disappears from
+     * every surface *and* the provider stops (or resumes) scheduling its
+     * reminders. Nothing is patched by hand — the provider notifies and the
+     * observer re-queries.
      */
-    fun setDisabled(id: Long, disabled: Boolean) {
-        viewModelScope.launch {
-            val current = prefs.disabledCalendarIds.first()
-            val next = if (disabled) current + id else current - id
-            if (next != current) {
-                prefs.setDisabledCalendarIds(next)
-                if (!disabled) recoverReminders(setOf(id))
-            }
-        }
+    fun setCalendarVisible(id: Long, visible: Boolean) = write {
+        repository.setCalendarsVisible(listOf(id), visible)
     }
 
     /**
-     * Enable or disable every calendar of one account in a single write — the
-     * "toggle all" affordance on an account header. Done as one set update so the
-     * per-calendar [setDisabled] calls can't race each other.
+     * Switch every calendar of one account on or off — the "toggle all"
+     * affordance on an account header. Each row is written on its own (the
+     * provider only re-arms reminder alarms for a single-id update), in one
+     * coroutine so the writes can't race each other.
      */
-    fun setAccountDisabled(ids: Collection<Long>, disabled: Boolean) {
-        viewModelScope.launch {
-            val current = prefs.disabledCalendarIds.first()
-            val next = if (disabled) current + ids else current - ids.toSet()
-            if (next != current) {
-                prefs.setDisabledCalendarIds(next)
-                if (!disabled) recoverReminders(current intersect ids.toSet())
-            }
-        }
-    }
-
-    /**
-     * Re-post the reminders that fired while [reEnabledIds] were disabled and are
-     * still relevant (event not yet over), then drop them from the stash. Runs
-     * after the disabled set is written, so the notifier's own disabled gate lets
-     * them through. Best-effort at re-enable time: it mirrors the receiver gates
-     * (reminders on + postable), and there is no later re-scan, so alerts left
-     * unposted because those gates are closed are simply released.
-     */
-    private suspend fun recoverReminders(reEnabledIds: Set<Long>) {
-        if (reEnabledIds.isEmpty()) return
-        val recovered = suppressedStore.recoverFor(reEnabledIds, System.currentTimeMillis())
-        if (recovered.isNotEmpty() &&
-            settingsPrefs.remindersEnabled.first() &&
-            notifier.canPost()
-        ) {
-            recovered.forEach { notifier.post(it) }
-        }
+    fun setAccountVisible(ids: Collection<Long>, visible: Boolean) = write {
+        repository.setCalendarsVisible(ids, visible)
     }
 
     // --- Automatic backup (issue #8) ------------------------------------

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditViewModel.kt

@@ -177,18 +177,16 @@ class EventEditViewModel @Inject constructor(
         repository.calendars().catch { emit(emptyList()) }
 
     /**
-     * Writable calendars — the only valid event targets. Disabled calendars are
-     * excluded, so you can't create into a calendar you've removed from the app;
-     * a last-used preselect landing on a now-disabled calendar falls back to the
-     * first remaining writable one (handled by [resolvedCalendarId] and [state]).
-     * Managed special-dates calendars are excluded too: their events are owned by
-     * the contact sync, which would delete any user event created there.
+     * Writable calendars — the only valid event targets. Calendars switched off
+     * in Settings → Calendars are excluded, so you can't create into one you've
+     * turned off; a last-used preselect landing on a now-off calendar falls back
+     * to the first remaining writable one (handled by [resolvedCalendarId] and
+     * [state]). Managed special-dates calendars are excluded too: their events
+     * are owned by the contact sync, which would delete any user event created
+     * there.
      */
-    private val writableCalendars: Flow<List<CalendarSource>> = combine(
-        allCalendars,
-        prefs.disabledCalendarIds,
-    ) { calendars, disabled ->
-        calendars.filter { it.canModifyContents && it.id !in disabled && !it.isManaged }
+    private val writableCalendars: Flow<List<CalendarSource>> = allCalendars.map { calendars ->
+        calendars.filter { it.canModifyContents && it.isVisibleInSystem && !it.isManaged }
     }
 
     /** The target calendar id, resolved exactly as the form shows it. */

app/src/main/java/de/jeanlucmakiola/calendula/ui/filter/FilterViewModel.kt

@@ -30,12 +30,11 @@ class FilterViewModel @Inject constructor(
         combine(
             repository.calendars(),
             prefs.hiddenCalendarIds,
-            prefs.disabledCalendarIds,
-        ) { calendars, hidden, disabled ->
-            // Disabled calendars are gone from the app entirely — they don't
-            // belong in the drawer's hide/show list (you can't hide what's
-            // already disabled). They live only in Settings → Calendars.
-            val enabled = calendars.filterNot { it.id in disabled }
+        ) { calendars, hidden ->
+            // Calendars switched off in Settings → Calendars are off device-wide
+            // and don't belong in the drawer's hide/show list (you can't hide
+            // what is already off). They live only in Settings → Calendars.
+            val enabled = calendars.filter { it.isVisibleInSystem }
             if (enabled.isEmpty()) {
                 FilterUiState.Failure(FailureReason.NoCalendarsConfigured)
             } else {

app/src/main/java/de/jeanlucmakiola/calendula/ui/imports/ImportViewModel.kt

@@ -7,7 +7,6 @@ import dagger.hilt.android.lifecycle.HiltViewModel
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.ics.IcsImporter
-import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
@@ -57,7 +56,6 @@ sealed interface ImportUiState {
 class ImportViewModel @Inject constructor(
     private val repository: CalendarRepository,
     private val importer: IcsImporter,
-    private val prefs: CalendarPrefs,
     @IoDispatcher private val io: CoroutineDispatcher,
 ) : ViewModel() {
 
@@ -87,16 +85,18 @@ class ImportViewModel @Inject constructor(
                     warnings = parsed.warnings,
                 )
                 else -> {
-                    // A disabled calendar is removed from the app, so it can't be
-                    // an import target — exclude it alongside the read-only ones.
-                    // Managed special-dates calendars are contact-derived and
-                    // editor-locked, so they're not a valid destination either.
-                    val disabled = prefs.disabledCalendarIds.first()
+                    // A calendar switched off in Settings → Calendars is off
+                    // everywhere, so it can't be an import target — exclude it
+                    // alongside the read-only ones. Managed special-dates
+                    // calendars are contact-derived and editor-locked, so
+                    // they're not a valid destination either.
                     ImportUiState.Many(
                         events = parsed.events,
                         warnings = parsed.warnings,
                         calendars = repository.calendars().first()
-                            .filter { it.canModifyContents && !it.isManaged && it.id !in disabled },
+                            .filter {
+                                it.canModifyContents && !it.isManaged && it.isVisibleInSystem
+                            },
                     )
                 }
             }

app/src/main/java/de/jeanlucmakiola/calendula/ui/permission/PermissionViewModel.kt

@@ -1,20 +1,29 @@
 package de.jeanlucmakiola.calendula.ui.permission
 
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.calendula.data.calendar.CalendarVisibilityReconciler
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
 import javax.inject.Inject
 
 @HiltViewModel
-class PermissionViewModel @Inject constructor() : ViewModel() {
+class PermissionViewModel @Inject constructor(
+    private val visibilityReconciler: CalendarVisibilityReconciler,
+) : ViewModel() {
 
     private val _state = MutableStateFlow<PermissionUiState>(PermissionUiState.Rationale)
     val state: StateFlow<PermissionUiState> = _state.asStateFlow()
 
     fun onGranted() {
         _state.value = PermissionUiState.Granted
+        // The visibility reconcile needs the calendar permissions, so the launch
+        // that started without them skipped it (#75) — this is the moment it can
+        // finally run. A no-op on a fresh install, where nothing is pending.
+        viewModelScope.launch { visibilityReconciler.run() }
     }
 
     fun onDenied() {

app/src/main/res/values-de/strings.xml

@@ -449,8 +449,6 @@
     <string name="settings_special_dates_disable_type_message">Dadurch werden der Kalender „%1$s“ und seine Ereignisse gelöscht. Alle von dir hinzugefügten Erinnerungen oder Notizen gehen verloren.</string>
     <string name="settings_special_dates_disable_confirm">Deaktivieren</string>
     <string name="dialog_save">Speichern</string>
-    <string name="calendars_disable_hint">Deaktiviere einen Kalender, um ihn aus der App zu entfernen – seine Ereignisse, Filter und Auswahlmöglichkeiten. Es wird nichts gelöscht und du kannst ihn hier jederzeit wieder aktivieren.</string>
-    <string name="calendars_show_in_app_a11y">„%1$s“ in der App anzeigen</string>
     <string name="calendars_account_menu_a11y">Weitere Optionen für %1$s</string>
     <string name="calendars_enable_all">Alle aktivieren</string>
     <string name="calendars_disable_all">Alle deaktivieren</string>

app/src/main/res/values-es/strings.xml

@@ -333,8 +333,6 @@
     <string name="calendars_local_header">Tus calendarios</string>
     <string name="calendars_local_empty">Sin calendarios locales todavia. Crea uno para mantener eventos solo en este dispositivo.</string>
     <string name="calendars_add">Añadir calendario</string>
-    <string name="calendars_disable_hint">Desactiva un calendario para removerlo de la aplicación — sus eventos, filtros y selectores. Nada se eliminara, y puedes reactivarlo en cualquier momento.</string>
-    <string name="calendars_show_in_app_a11y">Mostrar \"%1$s\" en la aplicación</string>
     <string name="calendars_synced_header">Calendarios sincronizados</string>
     <string name="calendars_synced_hint">Estos provienen de cuentas en tu dispositivo. Crea o editalos en su propia aplicación.</string>
     <string name="calendars_manage_in_app">Gestionar en aplicación</string>

app/src/main/res/values-fr/strings.xml

@@ -400,8 +400,6 @@
     <string name="calendars_local_header">Vos calendriers</string>
     <string name="calendars_local_empty">Pas encore de calendrier local. Créez-en un pour conserver les événements uniquement sur cet appareil.</string>
     <string name="calendars_add">Ajouter un calendrier</string>
-    <string name="calendars_disable_hint">Désactivez un calendrier pour le retirer de l’application, ses événements, ses filtres et ses sélecteurs. Rien n’est supprimé et vous pouvez le réactiver à tout moment ici.</string>
-    <string name="calendars_show_in_app_a11y">Afficher « %1$s » dans l’application</string>
     <string name="calendars_synced_header">Calendriers synchronisés</string>
     <string name="calendars_synced_hint">Ils proviennent de comptes sur votre appareil. Créez et modifiez-les dans leur propre application.</string>
     <string name="calendars_manage_in_app">Gérer dans l’application</string>

app/src/main/res/values-it/strings.xml

@@ -317,8 +317,6 @@
     <string name="calendars_local_header">Calendari locali</string>
     <string name="calendars_local_empty">Non ci sono ancora calendari locali. Creane uno con eventi salvati solo su questo dispositivo.</string>
     <string name="calendars_add">Aggiungi calendario</string>
-    <string name="calendars_disable_hint">Disattiva un calendario per non vederlo più sull\'app. Non viene cancellato nulla, puoi riattivarlo in qualsiasi momento.</string>
-    <string name="calendars_show_in_app_a11y">Mostra \"%1$s\" nell\'app</string>
     <string name="calendars_synced_header">Calendari sincronizzati</string>
     <string name="calendars_synced_hint">Questi calendari vengono dagli account sincronizzati sul tuo dispositivo. Puoi modificarli o crearne di nuovi dall\'app di sincronizzazione.</string>
     <string name="calendars_manage_in_app">Gestisci in app</string>

app/src/main/res/values-pl/strings.xml

@@ -396,8 +396,6 @@
     <string name="calendars_local_header">Twoje kalendarze</string>
     <string name="calendars_local_empty">Brak lokalnych kalendarzy. Utwórz kalendarz, aby zapisywać wydarzenia tylko na tym urządzeniu.</string>
     <string name="calendars_add">Dodaj kalendarz</string>
-    <string name="calendars_disable_hint">Wyłącz kalendarz, aby ukryć go w aplikacji — wraz z jego wydarzeniami, filtrami i selektorami. Nic nie zostanie usunięte, a w każdej chwili możesz go tutaj ponownie włączyć.</string>
-    <string name="calendars_show_in_app_a11y">Pokaż „%1$s” w aplikacji</string>
     <string name="calendars_synced_header">Synchronizowane kalendarze</string>
     <string name="calendars_synced_hint">Pochodzą z kont na Twoim urządzeniu. Możesz je tworzyć i edytować w powiązanych z nimi aplikacjach.</string>
     <string name="calendars_manage_in_app">Zarządzaj w aplikacji</string>

app/src/main/res/values/strings.xml

@@ -473,8 +473,10 @@
     <string name="calendars_local_header">Your calendars</string>
     <string name="calendars_local_empty">No local calendars yet. Create one to keep events on this device only.</string>
     <string name="calendars_add">Add calendar</string>
-    <string name="calendars_disable_hint">Turn a calendar off to remove it from the app — its events, filters and pickers. Nothing is deleted, and you can turn it back on here anytime.</string>
-    <string name="calendars_show_in_app_a11y">Show \"%1$s\" in the app</string>
+    <string name="calendars_visibility_hint">Turn a calendar off to hide it on this device — its events disappear from the app and it stops reminding you. This is the same switch your other calendar apps use, so they hide it too. Nothing is deleted, no other device is affected, and you can turn it back on here anytime.</string>
+    <string name="calendars_visibility_a11y">Show \"%1$s\"</string>
+    <string name="calendars_visibility_notice_title">Some calendars are switched off</string>
+    <string name="calendars_visibility_notice_message">Calendula now shows the calendars that are switched on for this device, so what you see and what reminds you can no longer disagree. Some of yours are currently off — they were switched off here or in another calendar app. Turn any of them back on in Settings → Calendars.</string>
     <string name="calendars_synced_header">Synced calendars</string>
     <string name="calendars_synced_hint">These come from accounts on your device. Create and edit them in their own app.</string>
     <string name="calendars_manage_in_app">Manage in app</string>

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/CalendarMapperTest.kt

@@ -15,6 +15,7 @@ class CalendarMapperTest {
         visible: Int = 1,
         accessLevel: Int = CalendarContract.Calendars.CAL_ACCESS_OWNER,
         description: String? = null,
+        syncEvents: Int? = 1,
     ): MapColumnReader = MapColumnReader(
         CalendarProjection.IDX_ID to id,
         CalendarProjection.IDX_DISPLAY_NAME to displayName,
@@ -24,6 +25,7 @@ class CalendarMapperTest {
         CalendarProjection.IDX_VISIBLE to visible,
         CalendarProjection.IDX_ACCESS_LEVEL to accessLevel,
         CalendarProjection.IDX_DESCRIPTION to description,
+        CalendarProjection.IDX_SYNC_EVENTS to syncEvents,
     )
 
     @Test
@@ -49,6 +51,18 @@ class CalendarMapperTest {
         )
     }
 
+    @Test
+    fun `sync_events 0 marks the calendar as not syncing its events`() {
+        assertThat(reader(syncEvents = 0).toCalendarSource().syncsEvents).isFalse()
+    }
+
+    @Test
+    fun `a NULL sync_events column is treated as syncing`() {
+        // The harmless default: it only ever holds the visibility migration back
+        // from switching a calendar on.
+        assertThat(reader(syncEvents = null).toCalendarSource().syncsEvents).isTrue()
+    }
+
     @Test
     fun `null displayName falls back to placeholder`() {
         val src = reader(displayName = null).toCalendarSource()

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImplTest.kt

@@ -12,6 +12,7 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.first
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.LocalDateTime
 import kotlinx.datetime.LocalTime
@@ -41,8 +42,12 @@ class CalendarRepositoryImplTest {
             produceFile = { tempDir.resolve("repo_test_prefs.preferences_pb").toFile() },
         )
 
-    private fun makeCal(id: Long, name: String = "Cal $id"): CalendarSource =
-        CalendarSource(id, name, "x@y", "LOCAL", 0xFF112233.toInt(), true)
+    private fun makeCal(
+        id: Long,
+        name: String = "Cal $id",
+        visible: Boolean = true,
+    ): CalendarSource =
+        CalendarSource(id, name, "x@y", "LOCAL", 0xFF112233.toInt(), visible)
 
     private fun makeEvent(
         id: Long,
@@ -171,37 +176,40 @@ class CalendarRepositoryImplTest {
     }
 
     @Test
-    fun `instances drops events whose calendar the user disabled`(@TempDir tempDir: Path) = runTest {
-        val prefs = newPrefs(tempDir)
-        prefs.setDisabledCalendarIds(setOf(2L))
+    fun `instances drops events whose calendar is hidden at system level`(
+        @TempDir tempDir: Path,
+    ) = runTest {
         val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L, visible = false))
             instancesResult = { _, _ ->
                 listOf(
-                    makeEvent(10L, "Enabled", calendarId = 1L),
-                    makeEvent(11L, "Disabled", calendarId = 2L),
+                    makeEvent(10L, "Shown", calendarId = 1L),
+                    makeEvent(11L, "Switched off", calendarId = 2L),
                 )
             }
         }
-        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
         repo.instances(range).test {
-            assertThat(awaitItem().map { it.title }).containsExactly("Enabled")
+            assertThat(awaitItem().map { it.title }).containsExactly("Shown")
             cancelAndIgnoreRemainingEvents()
         }
     }
 
     @Test
-    fun `instances applies the union of hidden and disabled sets`(@TempDir tempDir: Path) = runTest {
+    fun `instances applies the union of hidden and system-invisible calendars`(
+        @TempDir tempDir: Path,
+    ) = runTest {
         val prefs = newPrefs(tempDir)
         prefs.setHiddenCalendarIds(setOf(2L))
-        prefs.setDisabledCalendarIds(setOf(3L))
         val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L), makeCal(3L, visible = false))
             instancesResult = { _, _ ->
                 listOf(
                     makeEvent(10L, "Shown", calendarId = 1L),
                     makeEvent(11L, "Hidden", calendarId = 2L),
-                    makeEvent(12L, "Disabled", calendarId = 3L),
+                    makeEvent(12L, "Switched off", calendarId = 3L),
                 )
             }
         }
@@ -215,9 +223,61 @@ class CalendarRepositoryImplTest {
     }
 
     @Test
-    fun `instances re-emits when the disabled set changes`(@TempDir tempDir: Path) = runTest {
+    fun `instances re-emit after a calendar is switched off in the provider`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
+            instancesResult = { _, _ ->
+                listOf(
+                    makeEvent(10L, "A", calendarId = 1L),
+                    makeEvent(11L, "B", calendarId = 2L),
+                )
+            }
+        }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
+
+        val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
+        repo.instances(range).test {
+            assertThat(awaitItem().map { it.title }).containsExactly("A", "B").inOrder()
+
+            // The write itself is what the provider notifies about; the observer
+            // tick is what makes the views re-query.
+            repo.setCalendarsVisible(listOf(2L), false)
+            fake.tick()
+
+            assertThat(awaitItem().map { it.title }).containsExactly("A")
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `setCalendarsVisible addresses each calendar on its own`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        // An _id IN (…) batch would skip the provider's own reminder-alarm
+        // reschedule, so every calendar must be written by appended id.
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L), makeCal(3L))
+        }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
+
+        repo.setCalendarsVisible(listOf(1L, 3L), false)
+
+        assertThat(fake.visibilityWrites).containsExactly(1L to false, 3L to false).inOrder()
+    }
+
+    @Test
+    fun `without write permission the switch is kept app-side and still filters`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        // READ granted, WRITE denied: the provider flag can't be written, so the
+        // choice is parked in the pending set — and honoured from there, or the
+        // user's switched-off calendars would come back on upgrade (#75).
         val prefs = newPrefs(tempDir)
         val fake = FakeCalendarDataSource().apply {
+            canWrite = false
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
             instancesResult = { _, _ ->
                 listOf(
                     makeEvent(10L, "A", calendarId = 1L),
@@ -231,13 +291,119 @@ class CalendarRepositoryImplTest {
         repo.instances(range).test {
             assertThat(awaitItem().map { it.title }).containsExactly("A", "B").inOrder()
 
-            prefs.setDisabledCalendarIds(setOf(2L))
+            repo.setCalendarsVisible(listOf(2L), false)
 
             assertThat(awaitItem().map { it.title }).containsExactly("A")
+            assertThat(fake.visibilityWrites).isEmpty()
+            assertThat(prefs.pendingDisabledCalendarIds.first()).containsExactly(2L)
             cancelAndIgnoreRemainingEvents()
         }
     }
 
+    @Test
+    fun `calendars reports a pending switch-off as off`(@TempDir tempDir: Path) = runTest {
+        // Otherwise the Settings switch would snap straight back on for a
+        // read-only install, and the pickers would keep offering the calendar.
+        val prefs = newPrefs(tempDir)
+        val fake = FakeCalendarDataSource().apply {
+            canWrite = false
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
+        }
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
+
+        repo.calendars().test {
+            assertThat(awaitItem().map { it.isVisibleInSystem }).containsExactly(true, true)
+
+            repo.setCalendarsVisible(listOf(2L), false)
+
+            assertThat(awaitItem().single { it.id == 2L }.isVisibleInSystem).isFalse()
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `switching a calendar back on without write permission retires its entry`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val prefs = newPrefs(tempDir)
+        prefs.addPendingDisabledCalendarIds(setOf(2L))
+        val fake = FakeCalendarDataSource().apply {
+            canWrite = false
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
+        }
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), Dispatchers.Unconfined)
+
+        repo.setCalendarsVisible(listOf(2L), true)
+
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEmpty()
+    }
+
+    @Test
+    fun `a provider write clears anything still pending for that calendar`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val prefs = newPrefs(tempDir)
+        prefs.addPendingDisabledCalendarIds(setOf(2L))
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
+        }
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), Dispatchers.Unconfined)
+
+        repo.setCalendarsVisible(listOf(2L), false)
+
+        assertThat(fake.visibilityWrites).containsExactly(2L to false)
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEmpty()
+    }
+
+    @Test
+    fun `one tick costs one calendar query however many collectors there are`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L))
+            instancesResult = { _, _ -> listOf(makeEvent(10L, "A", calendarId = 1L)) }
+        }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
+
+        val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
+        repo.calendars().test {
+            awaitItem()
+            repo.instances(range).test {
+                awaitItem()
+                // Both flows listed/filtered off the same snapshot.
+                assertThat(fake.calendarQueries).isEqualTo(1)
+                cancelAndIgnoreRemainingEvents()
+            }
+
+            // The next tick invalidates it — one fresh read, not one per flow.
+            fake.tick()
+            awaitItem()
+            assertThat(fake.calendarQueries).isEqualTo(2)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `searchEvents drops results from calendars that are off or hidden`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val prefs = newPrefs(tempDir)
+        prefs.setHiddenCalendarIds(setOf(3L))
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(makeCal(1L), makeCal(2L, visible = false), makeCal(3L))
+            searchResult = {
+                listOf(
+                    makeEvent(10L, "Shown", calendarId = 1L),
+                    makeEvent(11L, "Switched off", calendarId = 2L),
+                    makeEvent(12L, "Hidden", calendarId = 3L),
+                )
+            }
+        }
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), Dispatchers.Unconfined)
+
+        assertThat(repo.searchEvents("e").map { it.title }).containsExactly("Shown")
+    }
+
     @Test
     fun `createEvent delegates and returns the new id`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply { nextInsertId = 77L }

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/FakeCalendarDataSource.kt

@@ -61,7 +61,14 @@ internal class FakeCalendarDataSource : CalendarDataSource {
 
     private val listeners = mutableListOf<() -> Unit>()
 
-    override fun calendars(): List<CalendarSource> = calendarsResult
+    /** How often [calendars] was queried — the repository shares one read per tick. */
+    var calendarQueries = 0
+        private set
+
+    override fun calendars(): List<CalendarSource> {
+        calendarQueries++
+        return calendarsResult
+    }
     override fun instances(beginMillis: Long, endMillis: Long): List<EventInstance> =
         instancesResult(beginMillis, endMillis)
     override fun searchEvents(query: String): List<EventInstance> = searchResult(query)
@@ -95,6 +102,27 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         updatedCalendars += UpdatedCalendar(id, displayName, color, description)
     }
 
+    /** (id, visible) pairs passed to [setCalendarVisible], in call order. */
+    val visibilityWrites = mutableListOf<Pair<Long, Boolean>>()
+
+    override fun setCalendarVisible(id: Long, visible: Boolean) {
+        writeError?.let { throw it }
+        visibilityWrites += id to visible
+        // Reflect the write so a follow-up [calendars] read sees it, the way the
+        // provider would once its notification has re-triggered the query.
+        calendarsResult = calendarsResult.map {
+            if (it.id == id) it.copy(isVisibleInSystem = visible) else it
+        }
+    }
+
+    /** Whether the fake holds `WRITE_CALENDAR`; false models a read-only grant. */
+    var canWrite: Boolean = true
+
+    override fun canWriteCalendars(): Boolean = canWrite
+
+    override fun isCalendarVisible(id: Long): Boolean? =
+        calendarsResult.firstOrNull { it.id == id }?.isVisibleInSystem
+
     override fun deleteCalendar(id: Long) {
         writeError?.let { throw it }
         deletedCalendarIds += id

app/src/test/java/de/jeanlucmakiola/calendula/data/prefs/CalendarPrefsTest.kt

@@ -52,32 +52,65 @@ class CalendarPrefsTest {
     }
 
     @Test
-    fun `disabledCalendarIds defaults to empty when unset`(@TempDir tempDir: Path) = runTest {
-        val prefs = CalendarPrefs(newDataStore(tempDir))
-        assertThat(prefs.disabledCalendarIds.first()).isEmpty()
+    fun `the pending disabled set reads back what an older version stored`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        // Same key as the retired app-local "disabled calendars" model: an
+        // upgrade inherits that set as switch-offs still owed to the provider.
+        val store = newDataStore(tempDir)
+        val prefs = CalendarPrefs(store)
+        store.updateData { p ->
+            p.toMutablePreferences().apply { this[CalendarPrefs.DISABLED_IDS_KEY] = "2,9" }
+        }
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEqualTo(setOf(2L, 9L))
     }
 
     @Test
-    fun `setDisabledCalendarIds round-trips through DataStore`(@TempDir tempDir: Path) = runTest {
+    fun `the pending disabled set is empty when nothing was ever stored`(
+        @TempDir tempDir: Path,
+    ) = runTest {
         val prefs = CalendarPrefs(newDataStore(tempDir))
-        prefs.setDisabledCalendarIds(setOf(1L, 42L, 7L))
-        assertThat(prefs.disabledCalendarIds.first()).isEqualTo(setOf(1L, 42L, 7L))
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEmpty()
     }
 
     @Test
-    fun `setting empty disabled set clears storage`(@TempDir tempDir: Path) = runTest {
+    fun `pending ids are added and dropped one at a time`(@TempDir tempDir: Path) = runTest {
         val prefs = CalendarPrefs(newDataStore(tempDir))
-        prefs.setDisabledCalendarIds(setOf(1L))
-        prefs.setDisabledCalendarIds(emptySet())
-        assertThat(prefs.disabledCalendarIds.first()).isEmpty()
+        prefs.addPendingDisabledCalendarIds(listOf(2L, 9L))
+        prefs.addPendingDisabledCalendarIds(listOf(4L))
+
+        prefs.removePendingDisabledCalendarIds(setOf(9L))
+
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEqualTo(setOf(2L, 4L))
     }
 
     @Test
-    fun `hidden and disabled sets are stored independently`(@TempDir tempDir: Path) = runTest {
+    fun `draining the pending set leaves the hidden set alone`(
+        @TempDir tempDir: Path,
+    ) = runTest {
         val prefs = CalendarPrefs(newDataStore(tempDir))
         prefs.setHiddenCalendarIds(setOf(1L))
-        prefs.setDisabledCalendarIds(setOf(2L))
+        prefs.addPendingDisabledCalendarIds(setOf(2L))
+
+        prefs.removePendingDisabledCalendarIds(setOf(2L))
+
+        assertThat(prefs.pendingDisabledCalendarIds.first()).isEmpty()
         assertThat(prefs.hiddenCalendarIds.first()).isEqualTo(setOf(1L))
-        assertThat(prefs.disabledCalendarIds.first()).isEqualTo(setOf(2L))
+    }
+
+    @Test
+    fun `the visibility notice is unevaluated until it is written`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        // Null is what makes the evaluation one-shot: "no" is stored just as
+        // firmly as "yes", so the notice can't resurface on a later launch.
+        val prefs = CalendarPrefs(newDataStore(tempDir))
+        assertThat(prefs.visibilityNoticePending.first()).isNull()
+
+        prefs.setVisibilityNoticePending(true)
+        assertThat(prefs.visibilityNoticePending.first()).isTrue()
+
+        prefs.setVisibilityNoticePending(false)
+        assertThat(prefs.visibilityNoticePending.first()).isFalse()
     }
 }

app/src/test/java/de/jeanlucmakiola/calendula/data/reminders/PostableAlertsTest.kt

@@ -1,71 +0,0 @@
-package de.jeanlucmakiola.calendula.data.reminders
-
-import com.google.common.truth.Truth.assertThat
-import org.junit.jupiter.api.Test
-
-class PostableAlertsTest {
-
-    private fun alert(alertId: Long, calendarId: Long) = ReminderAlert(
-        alertId = alertId,
-        eventId = alertId * 10,
-        calendarId = calendarId,
-        beginMillis = 0L,
-        endMillis = 0L,
-        title = "Event $alertId",
-        location = null,
-        isAllDay = false,
-    )
-
-    @Test
-    fun `keeps alerts when no calendar is disabled`() {
-        val due = listOf(alert(1, calendarId = 100), alert(2, calendarId = 200))
-
-        val postable = postableAlerts(due, disabledCalendarIds = emptySet())
-
-        assertThat(postable).isEqualTo(due)
-    }
-
-    @Test
-    fun `drops alerts for a disabled calendar`() {
-        val keep = alert(1, calendarId = 100)
-        val drop = alert(2, calendarId = 200)
-
-        val postable = postableAlerts(listOf(keep, drop), disabledCalendarIds = setOf(200))
-
-        assertThat(postable).containsExactly(keep)
-    }
-
-    @Test
-    fun `drops every alert when all their calendars are disabled`() {
-        val due = listOf(alert(1, calendarId = 100), alert(2, calendarId = 100))
-
-        val postable = postableAlerts(due, disabledCalendarIds = setOf(100))
-
-        assertThat(postable).isEmpty()
-    }
-
-    @Test
-    fun `keeps multiple alerts from the same enabled calendar`() {
-        val due = listOf(alert(1, calendarId = 100), alert(2, calendarId = 100))
-
-        val postable = postableAlerts(due, disabledCalendarIds = setOf(999))
-
-        assertThat(postable).isEqualTo(due)
-    }
-
-    @Test
-    fun `alert with unknown calendar id 0 is never treated as disabled`() {
-        // Pre-upgrade snooze PendingIntents carry no calendar id (defaults to 0L).
-        val preUpgrade = alert(1, calendarId = 0L)
-
-        assertThat(preUpgrade.isForDisabledCalendar(disabledCalendarIds = setOf(0L))).isFalse()
-        assertThat(postableAlerts(listOf(preUpgrade), disabledCalendarIds = setOf(0L)))
-            .containsExactly(preUpgrade)
-    }
-
-    @Test
-    fun `isForDisabledCalendar matches only the disabled ids`() {
-        assertThat(alert(1, calendarId = 200).isForDisabledCalendar(setOf(200))).isTrue()
-        assertThat(alert(1, calendarId = 100).isForDisabledCalendar(setOf(200))).isFalse()
-    }
-}

app/src/test/java/de/jeanlucmakiola/calendula/data/reminders/SuppressedReminderStoreTest.kt

@@ -1,129 +0,0 @@
-package de.jeanlucmakiola.calendula.data.reminders
-
-import androidx.datastore.core.DataStore
-import androidx.datastore.preferences.core.PreferenceDataStoreFactory
-import androidx.datastore.preferences.core.Preferences
-import com.google.common.truth.Truth.assertThat
-import kotlinx.coroutines.test.runTest
-import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.io.TempDir
-import java.nio.file.Path
-
-class SuppressedReminderStoreTest {
-
-    private fun newDataStore(tempDir: Path): DataStore<Preferences> =
-        PreferenceDataStoreFactory.create(
-            produceFile = { tempDir.resolve("test_prefs.preferences_pb").toFile() },
-        )
-
-    private fun alert(
-        alertId: Long,
-        calendarId: Long,
-        endMillis: Long = Long.MAX_VALUE,
-        title: String = "Event $alertId",
-        location: String? = null,
-    ) = ReminderAlert(
-        alertId = alertId,
-        eventId = alertId * 10,
-        calendarId = calendarId,
-        beginMillis = 0L,
-        endMillis = endMillis,
-        title = title,
-        location = location,
-        isAllDay = false,
-    )
-
-    @Test
-    fun `encode then decode round-trips every field including delimiters`() {
-        val original = alert(
-            alertId = 7,
-            calendarId = 42,
-            endMillis = 123_456_789L,
-            // Free-text with the field separator and other awkward characters.
-            title = "Lunch | with | Alice",
-            location = "Café, 3rd floor | room B",
-        ).copy(beginMillis = 100L, isAllDay = true)
-
-        val decoded = decodeStashEntry(encodeStashEntry(original))
-
-        assertThat(decoded).isEqualTo(original)
-    }
-
-    @Test
-    fun `decode returns null for a malformed entry`() {
-        assertThat(decodeStashEntry("not-a-valid-entry")).isNull()
-    }
-
-    @Test
-    fun `null location round-trips`() {
-        val original = alert(1, calendarId = 1, location = null)
-        assertThat(decodeStashEntry(encodeStashEntry(original))).isEqualTo(original)
-    }
-
-    @Test
-    fun `recoverFor returns and removes only the re-enabled calendars`() = runTest {
-        val store = SuppressedReminderStore(newDataStore(tempDir))
-        val keep = alert(1, calendarId = 100)
-        val recoverA = alert(2, calendarId = 200)
-        val recoverB = alert(3, calendarId = 200)
-        store.stash(listOf(keep, recoverA, recoverB), nowMillis = 0L)
-
-        val recovered = store.recoverFor(setOf(200L), nowMillis = 0L)
-
-        assertThat(recovered).containsExactly(recoverA, recoverB)
-        // The still-disabled calendar's alert stays stashed; the recovered ones are gone.
-        assertThat(store.recoverFor(setOf(100L, 200L), nowMillis = 0L)).containsExactly(keep)
-    }
-
-    @Test
-    fun `stash drops alerts whose event already ended`() = runTest {
-        val store = SuppressedReminderStore(newDataStore(tempDir))
-        val past = alert(1, calendarId = 100, endMillis = 500L)
-        val future = alert(2, calendarId = 100, endMillis = 2_000L)
-
-        store.stash(listOf(past, future), nowMillis = 1_000L)
-
-        assertThat(store.recoverFor(setOf(100L), nowMillis = 1_000L)).containsExactly(future)
-    }
-
-    @Test
-    fun `purgeExpired removes only entries past their event end`() = runTest {
-        val store = SuppressedReminderStore(newDataStore(tempDir))
-        // Stash both before "now" so neither is dropped on write, then advance time.
-        store.stash(
-            listOf(
-                alert(1, calendarId = 100, endMillis = 500L),
-                alert(2, calendarId = 100, endMillis = 2_000L),
-            ),
-            nowMillis = 0L,
-        )
-
-        store.purgeExpired(nowMillis = 1_000L)
-
-        assertThat(store.recoverFor(setOf(100L), nowMillis = 0L).map { it.alertId })
-            .containsExactly(2L)
-    }
-
-    @Test
-    fun `stash replaces an existing entry with the same alert id`() = runTest {
-        val store = SuppressedReminderStore(newDataStore(tempDir))
-        store.stash(listOf(alert(1, calendarId = 100, title = "old")), nowMillis = 0L)
-        store.stash(listOf(alert(1, calendarId = 100, title = "new")), nowMillis = 0L)
-
-        val recovered = store.recoverFor(setOf(100L), nowMillis = 0L)
-
-        assertThat(recovered).hasSize(1)
-        assertThat(recovered.single().title).isEqualTo("new")
-    }
-
-    @Test
-    fun `isRelevantAt is true up to the event end and false after`() {
-        val a = alert(1, calendarId = 1, endMillis = 1_000L)
-        assertThat(a.isRelevantAt(999L)).isTrue()
-        assertThat(a.isRelevantAt(1_000L)).isTrue()
-        assertThat(a.isRelevantAt(1_001L)).isFalse()
-    }
-
-    @TempDir
-    lateinit var tempDir: Path
-}

app/src/test/java/de/jeanlucmakiola/calendula/domain/CalendarVisibilityPlanTest.kt

@@ -0,0 +1,124 @@
+package de.jeanlucmakiola.calendula.domain
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+/**
+ * Draining the app's pending "switched off" set into the system's
+ * `Calendars.VISIBLE` (#75) — including the set an upgrade inherits from the
+ * retired app-local visibility model.
+ */
+class CalendarVisibilityPlanTest {
+
+    private fun cal(
+        id: Long,
+        visible: Boolean = true,
+        local: Boolean = false,
+        syncsEvents: Boolean = true,
+    ): CalendarSource = CalendarSource(
+        id = id,
+        displayName = "Cal $id",
+        accountName = "acc@local",
+        accountType = if (local) "LOCAL" else "com.google",
+        color = 0,
+        isVisibleInSystem = visible,
+        isLocal = local,
+        syncsEvents = syncsEvents,
+    )
+
+    @Test
+    fun `a pending calendar is switched off at system level`() {
+        val plan = calendarVisibilityPlan(listOf(cal(1L, visible = true)), setOf(1L))
+        assertThat(plan.hide).containsExactly(1L)
+        assertThat(plan.settled).isEmpty()
+    }
+
+    @Test
+    fun `a calendar hidden at system level is never switched on`() {
+        // The plan only hides: switching it on would un-hide the calendar in
+        // every other calendar app and start firing its reminders.
+        val plan = calendarVisibilityPlan(listOf(cal(1L, visible = false)), emptySet())
+        assertThat(plan.isEmpty).isTrue()
+    }
+
+    @Test
+    fun `a not-synced calendar is switched off like any other`() {
+        val plan = calendarVisibilityPlan(
+            listOf(cal(1L, visible = true, syncsEvents = false)),
+            setOf(1L),
+        )
+        assertThat(plan.hide).containsExactly(1L)
+    }
+
+    @Test
+    fun `a pending calendar already switched off is settled without a write`() {
+        val plan = calendarVisibilityPlan(listOf(cal(1L, visible = false)), setOf(1L))
+        assertThat(plan.hide).isEmpty()
+        assertThat(plan.settled).containsExactly(1L)
+    }
+
+    @Test
+    fun `a pending id for a calendar that no longer exists is settled`() {
+        val plan = calendarVisibilityPlan(listOf(cal(1L)), setOf(99L))
+        assertThat(plan.hide).isEmpty()
+        assertThat(plan.settled).containsExactly(99L)
+    }
+
+    @Test
+    fun `an empty pending set writes nothing`() {
+        val plan = calendarVisibilityPlan(listOf(cal(1L), cal(2L, visible = false)), emptySet())
+        assertThat(plan.isEmpty).isTrue()
+    }
+
+    @Test
+    fun `a mixed device splits into writes and settled ids`() {
+        val plan = calendarVisibilityPlan(
+            listOf(
+                cal(1L, visible = true), // not pending → untouched
+                cal(2L, visible = false), // hidden elsewhere → untouched
+                cal(3L, visible = true), // pending → hide
+                cal(4L, visible = false), // pending, already off → settled
+            ),
+            pendingDisabledIds = setOf(3L, 4L, 77L),
+        )
+        assertThat(plan.hide).containsExactly(3L)
+        assertThat(plan.settled).containsExactly(4L, 77L)
+    }
+
+    @Test
+    fun `a calendar hidden outside the app arms the notice`() {
+        assertThat(
+            hasSystemHiddenCalendars(listOf(cal(1L), cal(2L, visible = false)), emptySet()),
+        ).isTrue()
+    }
+
+    @Test
+    fun `a calendar we are about to hide ourselves does not arm the notice`() {
+        // It is off because the user switched it off here — nothing to explain.
+        assertThat(
+            hasSystemHiddenCalendars(listOf(cal(1L, visible = false)), setOf(1L)),
+        ).isFalse()
+    }
+
+    @Test
+    fun `an all-visible device does not arm the notice`() {
+        assertThat(hasSystemHiddenCalendars(listOf(cal(1L), cal(2L)), emptySet())).isFalse()
+    }
+
+    @Test
+    fun `a device-local calendar is treated like any other`() {
+        // Its sync_events flag says nothing about whether it holds events, so
+        // neither the plan nor the notice may reason about it.
+        val plan = calendarVisibilityPlan(
+            listOf(cal(1L, visible = true, local = true, syncsEvents = false)),
+            setOf(1L),
+        )
+        assertThat(plan.hide).containsExactly(1L)
+        assertThat(
+            hasSystemHiddenCalendars(
+                listOf(cal(2L, visible = false, local = true, syncsEvents = false)),
+                emptySet(),
+            ),
+        ).isTrue()
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/ui/edit/EventEditViewModelTest.kt

@@ -45,9 +45,9 @@ class EventEditViewModelTest {
     private val beginMillis = 1_781_164_800_000L
     private val endMillis = beginMillis + 3_600_000L
 
-    private fun cal(id: Long): CalendarSource = CalendarSource(
+    private fun cal(id: Long, visible: Boolean = true): CalendarSource = CalendarSource(
         id = id, displayName = "Cal $id", accountName = "acc@local", accountType = "LOCAL",
-        color = 0xFF112233.toInt(), isVisibleInSystem = true, canModifyContents = true,
+        color = 0xFF112233.toInt(), isVisibleInSystem = visible, canModifyContents = true,
     )
 
     private fun detail(calendarId: Long, rrule: String? = null): EventDetail = EventDetail(
@@ -90,6 +90,24 @@ class EventEditViewModelTest {
     /** Keep [EventEditViewModel.state] hot so it computes while the test drives it. */
     private fun CoroutineScope.activate(vm: EventEditViewModel): Job = launch { vm.state.collect {} }
 
+    @Test
+    fun `a calendar switched off in settings is not offered as a target`(
+        @TempDir tempDir: Path,
+    ) = runTest(dispatcher) {
+        val fake = FakeCalendarDataSource().apply {
+            calendarsResult = listOf(cal(1L), cal(2L, visible = false))
+            eventDetailResult = { detail(calendarId = 1L) }
+        }
+        val vm = viewModel(tempDir, fake)
+        val job = activate(vm)
+
+        vm.openForEdit(eventId = 42L, beginMillis = beginMillis, endMillis = endMillis)
+        advanceUntilIdle()
+
+        assertThat(vm.state.value?.calendars?.map { it.id }).containsExactly(1L)
+        job.cancel()
+    }
+
     @Test
     fun `changing the calendar routes the save through a move, not an update`(
         @TempDir tempDir: Path,

docs/ARCHITECTURE.md

@@ -157,6 +157,23 @@ sequenceDiagram
 Posting happens before marking: a crash in between re-posts silently (same
 tag + `setOnlyAlertOnce`) rather than losing a reminder. Swiped
 notifications never return because `FIRED` rows are never re-queried.
+
+**One visibility model.** The provider only schedules alarms for calendars with
+`Calendars.VISIBLE = 1`, so that flag *is* the app's on/off switch: Settings →
+Calendars writes it (one calendar per update — `CalendarProvider2` skips its own
+`checkNextAlarm()` reschedule for any selection that isn't `_id=`), and every
+display predicate reads `CalendarSource.isVisibleInSystem`. The reconciliation
+runs one way only: a calendar the user switched off in Calendula is switched off
+in the provider, never the reverse — un-hiding one would reach into every other
+calendar app on the device — and a one-time notice explains the calendars that
+were already off. `CalendarPrefs.pendingDisabledCalendarIds` holds the switch-offs
+the app has not been allowed to write yet (read-only permission grant, or a
+pre-permission launch); `CalendarVisibilityReconciler` drains it entry by entry,
+and until it does, the repository and `ReminderNotifier.post` honour it. That
+gate also covers a snooze re-shown from our own alarm after its calendar was
+switched off. The drawer's filter sheet (`CalendarPrefs.hiddenCalendarIds`) is a
+separate in-app declutter that never touches reminders. See
+`docs/design/calendar-visibility-model.md`.
 Deliberately absent until real devices prove it necessary: own alarm
 scheduling, `BOOT_COMPLETED`, snooze/dismiss actions, battery-exemption
 prompts.

docs/design/calendar-visibility-model.md

@@ -0,0 +1,224 @@
+# Design: One calendar-visibility model (reminders silently never fire)
+
+Status: **implemented** on `fix/calendar-visibility-model` (on-device review owed)
+Date: 2026-07-25, revised 2026-07-25 after code review
+
+Built as specified, then revised in two places the review found (see §4, §6):
+the reconciliation no longer switches calendars *on*, and a calendar switched
+off without `WRITE_CALENDAR` is kept app-side instead of being lost. Other
+notes: `CalendarSource` gained a `syncsEvents` flag (read for #76's "not synced"
+label); the reconcile runs from `CalendulaApp.onCreate` *and* from
+`PermissionViewModel.onGranted`, so a launch that starts without the calendar
+permissions still catches up the moment they are granted; and the Settings hint
+string was reworded rather than dropped — it described the retired app-only
+behaviour, so leaving it would have been the one piece of false text on screen.
+Tracking: Codeberg #75. Split out of this work: #76 (read-only / not-synced
+communication), #77 (accounts merged by name).
+
+## The bug
+
+Reminders never arrive for a calendar that is hidden at system level, and nothing
+in the app hints at it. The event shows up, its reminders are listed on the detail
+screen, and no notification ever fires.
+
+The cause is a design defect, not a device quirk: the app has **two** visibility
+models. Calendula's own `disabledCalendarIds` decides what it shows, while the
+system's `Calendars.VISIBLE` decides whether the provider schedules reminder alarms
+at all. The app reads `VISIBLE` into `CalendarSource.isVisibleInSystem` and then
+never uses it — `calendars()` queries with a `null` selection. So the two models can
+disagree indefinitely, and when they do, reminder delivery dies quietly.
+
+Not a regression (nothing in `data/reminders/` changed in 2.14/2.15) and not
+Android-10-specific — the gate is identical on every supported version.
+
+## Verified provider behaviour
+
+Checked against AOSP source and empirically on device; details in the
+`calendars-visible-flag-facts` note.
+
+- AOSP `CalendarAlarmManager.scheduleNextAlarmLocked` selects reminders with
+  `WHERE Calendars.VISIBLE=1 AND … AND Reminders.METHOD=1`, and its cleanup
+  selector *deletes* `CalendarAlerts` rows whose event has `visible=0`. Identical in
+  the android10, android13 and android15 branches.
+- `VISIBLE` is one of only three `Calendars` columns Android documents as "writable
+  by both an app and a sync adapter" (with `CALENDAR_DISPLAY_NAME` and
+  `SYNC_EVENTS`). Writing it is sanctioned, not a workaround.
+- **`VISIBLE` is device-local.** Google's sync adapter neither pushes a local change
+  upstream nor overwrites one on a later sync — verified by flipping a Google
+  account's primary calendar, forcing the upload sync (the adapter cleared
+  `DIRTY`/`MUTATORS`) and observing no change on the web, and by forcing a full sync
+  carrying `sync_extra_get_settings=true` without the local value being reverted. The
+  adapter only seeds the initial value at calendar creation. Caveat: a negative
+  observation, so "no propagation seen where it would have been visible" rather than
+  proof of impossibility.
+- `VISIBLE` and `SYNC_EVENTS` are independent. `visible=1, sync_events=0` is
+  reachable and persistent: a calendar that looks enabled everywhere and is
+  permanently empty, because its events are not on the device at all.
+
+## Decision
+
+Collapse to one model, the way Etar does it — the Settings → Calendars toggle *is*
+`Calendars.VISIBLE`.
+
+The two existing levels map onto it directly:
+
+| Level | Before | After |
+| --- | --- | --- |
+| Filter sheet | `hiddenCalendarIds` (app-local) | unchanged |
+| Settings → Calendars | `disabledCalendarIds` (app-local) | `Calendars.VISIBLE` |
+
+The filter sheet stays a purely in-app declutter toggle and deliberately does **not**
+suppress reminders — hiding a calendar from view is not the same as asking not to be
+reminded. Settings-off does stop reminders, because the provider then schedules
+nothing.
+
+Rejected alternatives:
+
+- **Own the reminder delivery (the Fossify model)** — schedule our own alarms so
+  `VISIBLE` stops mattering. Bigger, and it leaves two visibility models in place.
+  Kept as a possible later step; see Non-goals.
+- **Warn about the mismatch** — a banner papering over two sources of truth rather
+  than removing one.
+- **Have the toggle write `SYNC_EVENTS` too** — turning it off makes the provider
+  drop the calendar's local events, so an innocuous switch becomes destructive. Never
+  written.
+
+No hint text and no confirmation dialog: the toggle now means "show this calendar",
+which is what a user assumes, and the change does not leave the device.
+
+## Work
+
+### 1. Write path
+
+- `CalendarDataSource.setCalendarVisible(id: Long, visible: Boolean)` — update
+  `ContentUris.withAppendedId(Calendars.CONTENT_URI, id)`, *not* the sync-adapter URI
+  (must work on synced calendars) and *not* a `WHERE _id IN (…)` batch. See the
+  gotcha below. Mirror in `FakeCalendarDataSource`; repository passthrough on `io`.
+- No manual UI patching: the `ContentObserver` re-queries, and the provider re-runs
+  `checkNextAlarm()` itself when `VISIBLE` changes. The observer-driven invariant
+  holds for free.
+
+> **Load-bearing gotcha.** `CalendarProvider2.updateInTransaction` returns early with
+> a raw `mDb.update()` unless the selection is `_id=?` or starts with `_id=`
+> (`:4281`). That early return skips the dirty marking, the `MUTATORS` stamp **and the
+> `checkNextAlarm()` reschedule at `:4314-4322`** — i.e. it would silently skip the
+> very reminder rescheduling this fix exists to trigger. Always address one calendar
+> by appended id. A batch of per-row `ContentProviderOperation`s is fine (those
+> generate `_id=n`, which the provider handles explicitly); a single IN-clause op is
+> not.
+
+### 2. Read path
+
+- Settings → Calendars row state derives from `isVisibleInSystem`.
+- Swap the display predicate from `id in disabledIds` to `!isVisibleInSystem` in
+  `CalendarRepositoryImpl.instances`/`searchEvents`, `EventEditViewModel` (form
+  picker), `ImportViewModel` (import picker).
+- `hiddenCalendarIds` keeps working exactly as it does today, unioned as before.
+
+### 3. Deletions
+
+With `VISIBLE=0` the provider creates no alert rows, so there is nothing to suppress,
+stash or recover. Remove:
+
+- `postableAlerts` / `isForDisabledCalendar` (`EventReminderReceiver.kt:29-41`)
+- `SuppressedReminderStore` and `CalendarsViewModel.recoverReminders`
+
+The gate in `ReminderNotifier.post` stays (review): two paths reach it without a
+provider alert row behind them — a snooze re-shown from our own exact alarm,
+scheduled before the calendar was switched off, and a read-only install whose
+switch lives in the pending set. One choke point covers both receivers.
+
+Net code reduction. Update the now-false KDoc on `CalendarPrefs` claiming the toggle
+"never touches the system's VISIBLE/SYNC_EVENTS flags, so other calendar apps are
+unaffected".
+
+### 4. Reconciliation (hide-only, standing)
+
+`CalendarVisibilityReconciler` runs on every launch and again when the permission
+screen grants the permissions. It drains
+`CalendarPrefs.pendingDisabledCalendarIds` — the retired `disabledCalendarIds`
+key, re-read under a new name — into the provider:
+
+- Pending **and** `visible=1` → write `visible=0`, then drop the id.
+- Pending but already `visible=0`, or gone from the device → drop the id.
+- Everything else untouched. Nothing is ever switched **on**.
+
+Each id leaves the set as its own write lands, so a run that dies part-way
+resumes where it stopped and can never re-apply a hide the user has since undone
+by hand. The set empties itself; no separate "migration done" flag exists.
+
+**Hide-only was the review's correction.** The first cut also switched calendars
+on (enabled in-app + `visible=0` + `sync_events=1` → `visible=1`) to keep the
+upgrade invisible. Two problems, both real:
+
+- `VISIBLE` is device-wide. "Not disabled in Calendula" is the default for every
+  calendar, including ones the user deliberately hid in Google Calendar, Etar or
+  DAVx5 — those would pop back there *and* start firing reminders nobody asked
+  for, from a switch the user never touched.
+- The `sync_events=1` guard doesn't hold. It is sound for sync-adapter accounts,
+  but an `ACCOUNT_TYPE_LOCAL` calendar another app created can sit at
+  `sync_events=0` while holding real device-local events, so the guard would have
+  hidden events it claimed could not exist.
+
+The cost is that events from a system-hidden calendar stop appearing in
+Calendula. That is confined to this app, visible and reversible in Settings →
+Calendars, and announced: on the first run that finds such a calendar, the
+reconciler arms a one-time dialog (`CalendarVisibilityNoticeDialog`) explaining
+that visibility now follows the device and where to change it. The answer —
+including "nothing to say" — is stored, so it can never resurface later.
+
+### 4b. No `WRITE_CALENDAR`
+
+Only `READ_CALENDAR` gates the app (`RootScreen`), and `PermissionScreen` says as
+much: declining write keeps Calendula usable read-only. Those users can't have
+the flag written for them, so the switch keeps working app-side —
+`CalendarRepositoryImpl.setCalendarsVisible` writes the pending set instead — and
+that set filters `instances`/`searchEvents` and gates `ReminderNotifier.post`
+exactly as `VISIBLE` would. If `WRITE_CALENDAR` ever arrives, the reconciler
+flushes it and the app-side copy disappears. This is the one place a second
+visibility model still exists, and it exists only where the first one is
+unwritable.
+
+### 5. `sync_events = 0` rows
+
+No toggle at all — flipping it cannot produce an event. The row still shows, labelled
+"not synced", sorted to the bottom of its account group regardless of alphabetical
+order, and dimmed using the screen's existing `dimmed`/`dimIf` convention. Consult
+the `material-3` skill before designing the label. **Tracked in #76**, not here.
+
+## Non-goals
+
+The missed-broadcast class of failure: a reminder lost because the provider's
+`EVENT_REMINDER` broadcast never arrives (OEM app-sleeping, an OEM-modified provider)
+or because a competing calendar app marked the alert `FIRED` first. There is no
+rescan, and `dueAlerts` only accepts `STATE_SCHEDULED`, so one missed broadcast loses
+that reminder permanently.
+
+If we take that on later, note that Etar's `AlarmScheduler` self-disables once a real
+`EVENT_REMINDER` is ever seen (`PROVIDER_REMINDER_PREF_KEY`) — **that latch must not
+be copied.** It assumes the only failure is "broadcast never arrives"; ours includes
+"broadcast arrives fine for other calendars, but no alert row was ever created". Any
+scheduler of ours must run unconditionally and dedupe by notification identity.
+
+## Testing
+
+All JVM-testable:
+
+- the reconciliation as a pure function over `(calendars, pendingIds)`: hide,
+  settled (already off / gone), never a switch-on, and the notice predicate
+- the display-predicate swap, and the pending set filtering alongside it
+- the read-only path: no provider write, the choice parked in the pending set,
+  events filtered from it
+- `FakeCalendarDataSource` assertions that `setCalendarVisible` addresses a single
+  calendar by id
+- one `Calendars` query per provider tick, however many flows are collecting
+
+On-device review before release (UI-touching). Local repro for the #75 shape: force a
+test calendar to `visible=0` via the provider, confirm its reminders stop and that
+the Settings toggle brings them back.
+
+## Release
+
+Behaviour change plus a migration and a device-wide-flag change, so this reads as a
+minor (2.17.0) rather than a patch. New strings land in `values/strings.xml` only;
+translations come back through Weblate.