feat(contacts): lock managed fields in the event editor

When editing an event in a special-dates calendar, the title, all-day/date and
recurrence are locked (the sync overwrites them) while reminders, location, notes
and colour stay editable — the field-level "managed" contract from the design.

- EventEditUiState.isManaged (calendar id ∈ managedCalendarIds while editing),
  wired through the ViewModel's state combine.
- InlineTextField/InlineField gain an `enabled` flag (dims + goes read-only);
  ScheduleRow dims and disables its date/time taps; the all-day switch and the
  recurrence card are disabled.
- A one-line "Managed by …" hint under the title explains what's editable.

The calendar picker needs no change — it's already create-only, and managed
events are always edits.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/InlineTextField.kt

@@ -36,6 +36,7 @@ fun InlineTextField(
     textStyle: TextStyle = MaterialTheme.typography.titleMedium,
     singleLine: Boolean = true,
     minLines: Int = 1,
+    enabled: Boolean = true,
     keyboardType: KeyboardType = KeyboardType.Text,
     capitalization: KeyboardCapitalization = KeyboardCapitalization.None,
     imeAction: ImeAction = ImeAction.Default,
@@ -43,15 +44,17 @@ fun InlineTextField(
     onImeAction: (() -> Unit)? = null,
 ) {
     val resolvedStyle = textStyle.copy(
-        color = if (textStyle.color.isSpecified) {
-            textStyle.color
-        } else {
-            MaterialTheme.colorScheme.onSurface
+        color = when {
+            // A disabled field reads as dimmed, like a locked value.
+            !enabled -> MaterialTheme.colorScheme.onSurfaceVariant
+            textStyle.color.isSpecified -> textStyle.color
+            else -> MaterialTheme.colorScheme.onSurface
         },
     )
     BasicTextField(
         value = value,
         onValueChange = onValueChange,
+        enabled = enabled,
         textStyle = resolvedStyle,
         singleLine = singleLine,
         minLines = minLines,

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

@@ -435,6 +435,10 @@ private fun EventEditContent(
     val form = state.form
     val locale = currentLocale()
     val dark = isSystemInDarkTheme()
+    // The title, date and recurrence are managed by the special-dates sync, so
+    // they're locked here; everything else (reminders, location, notes) is the
+    // user's to edit.
+    val locked = state.isManaged
     var picker by remember { mutableStateOf<PickerTarget?>(null) }
     var showCalendarPicker by rememberSaveable { mutableStateOf(false) }
     var showReminderPicker by rememberSaveable { mutableStateOf(false) }
@@ -519,6 +523,7 @@ private fun EventEditContent(
             placeholder = stringResource(R.string.event_edit_title_hint),
             textStyle = MaterialTheme.typography.headlineMedium
                 .copy(fontWeight = FontWeight.SemiBold),
+            enabled = !locked,
             modifier = Modifier
                 .fillMaxWidth()
                 .padding(vertical = 4.dp)
@@ -531,6 +536,17 @@ private fun EventEditContent(
                 .height(3.dp)
                 .background(accent, RoundedCornerShape(2.dp)),
         )
+        if (locked) {
+            Spacer(Modifier.height(10.dp))
+            Text(
+                text = stringResource(
+                    R.string.event_edit_managed_hint,
+                    selectedCalendar?.displayName.orEmpty(),
+                ),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
 
         Spacer(Modifier.height(20.dp))
 
@@ -549,7 +565,11 @@ private fun EventEditContent(
                         style = MaterialTheme.typography.titleMedium,
                         modifier = Modifier.weight(1f),
                     )
-                    Switch(checked = form.isAllDay, onCheckedChange = viewModel::setAllDay)
+                    Switch(
+                        checked = form.isAllDay,
+                        onCheckedChange = viewModel::setAllDay,
+                        enabled = !locked,
+                    )
                 }
             },
         ) {
@@ -561,6 +581,7 @@ private fun EventEditContent(
                 locale = locale,
                 onDateClick = { picker = PickerTarget.StartDate },
                 onTimeClick = { picker = PickerTarget.StartTime },
+                enabled = !locked,
             )
             ScheduleRow(
                 label = stringResource(R.string.event_edit_ends),
@@ -570,6 +591,7 @@ private fun EventEditContent(
                 onDateClick = { picker = PickerTarget.EndDate },
                 onTimeClick = { picker = PickerTarget.EndTime },
                 isError = EventFormProblem.EndBeforeStart in state.problems,
+                enabled = !locked,
             )
             if (EventFormProblem.EndBeforeStart in state.problems) {
                 Spacer(Modifier.height(2.dp))
@@ -700,7 +722,7 @@ private fun EventEditContent(
             EditCard(
                 icon = Icons.Default.Repeat,
                 iconContentDescription = null,
-                onClick = { showRecurrencePicker = true },
+                onClick = if (locked) null else ({ showRecurrencePicker = true }),
             ) {
                 Row(
                     verticalAlignment = Alignment.CenterVertically,
@@ -1858,6 +1880,7 @@ private fun InlineField(
     textStyle: TextStyle = MaterialTheme.typography.titleMedium,
     singleLine: Boolean = true,
     minLines: Int = 1,
+    enabled: Boolean = true,
     keyboardType: KeyboardType = KeyboardType.Text,
     modifier: Modifier = Modifier
         .fillMaxWidth()
@@ -1871,6 +1894,7 @@ private fun InlineField(
         textStyle = textStyle,
         singleLine = singleLine,
         minLines = minLines,
+        enabled = enabled,
         keyboardType = keyboardType,
     )
 }
@@ -1885,6 +1909,7 @@ private fun ScheduleRow(
     onDateClick: () -> Unit,
     onTimeClick: () -> Unit,
     isError: Boolean = false,
+    enabled: Boolean = true,
 ) {
     val dateFormat = remember(locale) {
         DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM).withLocale(locale)
@@ -1894,11 +1919,12 @@ private fun ScheduleRow(
         timeOfDayFormatter(use24Hour, locale)
     }
     // Tappable values read as links (primary), like the location on the
-    // detail screen; errors flip them to the error colour.
-    val valueColor = if (isError) {
-        MaterialTheme.colorScheme.error
-    } else {
-        MaterialTheme.colorScheme.primary
+    // detail screen; errors flip them to the error colour; a locked (managed)
+    // row dims to a plain, non-tappable value.
+    val valueColor = when {
+        !enabled -> MaterialTheme.colorScheme.onSurfaceVariant
+        isError -> MaterialTheme.colorScheme.error
+        else -> MaterialTheme.colorScheme.primary
     }
     Row(
         verticalAlignment = Alignment.CenterVertically,
@@ -1915,7 +1941,7 @@ private fun ScheduleRow(
             style = MaterialTheme.typography.titleMedium,
             color = valueColor,
             modifier = Modifier
-                .clickable(onClick = onDateClick)
+                .clickable(enabled = enabled, onClick = onDateClick)
                 .padding(vertical = 8.dp, horizontal = 6.dp),
         )
         if (!isAllDay) {
@@ -1924,7 +1950,7 @@ private fun ScheduleRow(
                 style = MaterialTheme.typography.titleMedium,
                 color = valueColor,
                 modifier = Modifier
-                    .clickable(onClick = onTimeClick)
+                    .clickable(enabled = enabled, onClick = onTimeClick)
                     .padding(vertical = 8.dp, horizontal = 6.dp),
             )
         }

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

@@ -29,6 +29,12 @@ data class EventEditUiState(
     val hiddenFields: List<EventFormField> = emptyList(),
     /** True while editing an existing event (the calendar is then fixed). */
     val isEditing: Boolean = false,
+    /**
+     * True when the event's calendar is a contact special-dates calendar the app
+     * manages. While editing such an event the title, date and recurrence are
+     * locked (sync overwrites them); reminders, location and notes stay editable.
+     */
+    val isManaged: Boolean = false,
     /**
      * Whether to focus the title and raise the keyboard when this is a fresh
      * create form (issue #10). Mirrors the settings flag; the screen only acts

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

@@ -165,7 +165,8 @@ class EventEditViewModel @Inject constructor(
             ::ExternalInputs,
         ).flowOn(io),
         colorPalette,
-    ) { local, external, palette ->
+        settingsPrefs.managedCalendarIds,
+    ) { local, external, palette, managedIds ->
         val form = local.form ?: return@combine null
         val resolvedId = form.calendarId
             ?: external.lastUsed?.takeIf { id -> external.writable.any { it.id == id } }
@@ -180,6 +181,8 @@ class EventEditViewModel @Inject constructor(
             visibleFields = visibleFields,
             hiddenFields = (EventFormField.entries.toSet() - visibleFields).sorted(),
             isEditing = local.editTarget != null,
+            // Editing an event in a managed calendar locks its synced fields.
+            isManaged = local.editTarget != null && resolvedId != null && resolvedId in managedIds,
             autofocusTitle = external.autofocusTitle,
             // A modified-occurrence exception can't carry its own rule, so
             // the scope dialog drops "only this event" after a rule change.