Add a setting to turn drag-to-reschedule off (#173)

Drag to move is on by default; turning it off drops the move scope, so no
event block registers a drag gesture at all.

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

@@ -301,6 +301,19 @@ class SettingsPrefs @Inject constructor(
         store.edit { it[TODAY_BUTTON_IN_TOOLBAR_KEY] = enabled }
     }
 
+    /**
+     * Whether events can be dragged to another slot in the calendar views (#68,
+     * #173). Defaults to ON. Off means no block registers a drag gesture at all;
+     * rescheduling then goes through the edit form.
+     */
+    val dragToReschedule: Flow<Boolean> = store.data.map { prefs ->
+        prefs[DRAG_TO_RESCHEDULE_KEY] ?: true
+    }
+
+    suspend fun setDragToReschedule(enabled: Boolean) {
+        store.edit { it[DRAG_TO_RESCHEDULE_KEY] = enabled }
+    }
+
     /**
      * How far ahead the in-app Agenda screen shows events (v2.11). Defaults to
      * [AgendaRange.Month] — a month of upcoming events. Independent of the
@@ -945,6 +958,7 @@ class SettingsPrefs @Inject constructor(
         internal val MONTH_VIEW_STYLE_KEY = stringPreferencesKey("month_view_style")
         internal val TIMELINE_SCALE_KEY = stringPreferencesKey("timeline_scale")
         internal val TODAY_BUTTON_IN_TOOLBAR_KEY = booleanPreferencesKey("today_button_in_toolbar")
+        internal val DRAG_TO_RESCHEDULE_KEY = booleanPreferencesKey("drag_to_reschedule")
         internal val DEFAULT_VIEW_KEY = stringPreferencesKey("default_view")
         internal val QUICK_SWITCH_VIEWS_KEY = stringPreferencesKey("quick_switch_views")
         internal val DRAWER_VIEW_ORDER_KEY = stringPreferencesKey("drawer_view_order")

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

@@ -312,6 +312,9 @@ fun CalendarHost(
         heldEditKey = key
         editKey = key
     }
+    // Off by preference (#173) means no scope at all: every block then registers
+    // no drag gesture, and the edit form stays the way to reschedule.
+    val dragToReschedule = viewModel.dragToReschedule.collectAsStateWithLifecycle().value
     val moveScope = remember(movableCalendarIds, reschedule) {
         EventMoveScope(
             movableCalendarIds = movableCalendarIds,
@@ -339,7 +342,7 @@ fun CalendarHost(
         // navigation, so it fades through rather than sliding — paging *within* a
         // view keeps the directional slide. AnimatedContent keyed on the view type.
         val viewSwitch = fadeThrough()
-        CompositionLocalProvider(LocalEventMove provides moveScope) {
+        CompositionLocalProvider(LocalEventMove provides moveScope.takeIf { dragToReschedule }) {
         AnimatedContent(
             targetState = view,
             transitionSpec = { viewSwitch },

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

@@ -53,4 +53,12 @@ class CalendarHostViewModel @Inject constructor(
             started = SharingStarted.WhileSubscribed(5_000L),
             initialValue = false,
         )
+
+    /** Whether events may be dragged to another slot to reschedule them (#68, #173). */
+    val dragToReschedule: StateFlow<Boolean> = prefs.dragToReschedule
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5_000L),
+            initialValue = true,
+        )
 }

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsUiState.kt

@@ -42,6 +42,8 @@ data class SettingsUiState(
     val showWeekNumbers: Boolean = false,
     /** Whether the jump-to-today control sits in the top bar instead of the FAB (#60). */
     val todayButtonInToolbar: Boolean = false,
+    /** Whether events can be dragged to another slot to reschedule them (#68, #173). */
+    val dragToReschedule: Boolean = true,
     /** How far ahead the in-app Agenda screen shows events (v2.11). */
     val agendaScreenRange: AgendaRange = AgendaRange.Month,
     /** How far ahead the agenda widget shows events (v2.11). */

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsViewModel.kt

@@ -145,9 +145,15 @@ class SettingsViewModel @Inject constructor(
                     prefs.showWeekNumbers,
                     prefs.agendaShowToday,
                     prefs.softenCalendarColors,
-                    prefs.todayButtonInToolbar,
+                    combine(
-                ) { hourLines, weekNumbers, showToday, soften, todayInToolbar ->
+                        prefs.todayButtonInToolbar,
-                    DisplayToggles(hourLines, weekNumbers, showToday, soften, todayInToolbar)
+                        prefs.dragToReschedule,
+                        ::Pair,
+                    ),
+                ) { hourLines, weekNumbers, showToday, soften, (todayInToolbar, dragToMove) ->
+                    DisplayToggles(
+                        hourLines, weekNumbers, showToday, soften, todayInToolbar, dragToMove,
+                    )
                 },
             ) { view, screenRange, widgetRange, timeFormat, toggles ->
                 ViewSettings(
@@ -157,6 +163,7 @@ class SettingsViewModel @Inject constructor(
                     agendaShowToday = toggles.agendaShowToday,
                     softenColors = toggles.softenColors,
                     todayButtonInToolbar = toggles.todayButtonInToolbar,
+                    dragToReschedule = toggles.dragToReschedule,
                 )
             },
             combine(
@@ -189,6 +196,7 @@ class SettingsViewModel @Inject constructor(
                 agendaShowToday = views.agendaShowToday,
                 softenColors = views.softenColors,
                 todayButtonInToolbar = views.todayButtonInToolbar,
+                dragToReschedule = views.dragToReschedule,
                 agendaShowRangeBar = misc.showRangeBar,
                 autofocusEventTitle = misc.autofocusEventTitle,
                 pastEventDisplay = misc.pastEventDisplay,
@@ -289,6 +297,7 @@ class SettingsViewModel @Inject constructor(
         val agendaShowToday: Boolean,
         val softenColors: Boolean,
         val todayButtonInToolbar: Boolean,
+        val dragToReschedule: Boolean,
     )
 
     private data class DisplayToggles(
@@ -297,6 +306,7 @@ class SettingsViewModel @Inject constructor(
         val agendaShowToday: Boolean,
         val softenColors: Boolean,
         val todayButtonInToolbar: Boolean,
+        val dragToReschedule: Boolean,
     )
 
     private data class MiscSettings(
@@ -534,6 +544,10 @@ class SettingsViewModel @Inject constructor(
         viewModelScope.launch { prefs.setTodayButtonInToolbar(enabled) }
     }
 
+    fun setDragToReschedule(enabled: Boolean) {
+        viewModelScope.launch { prefs.setDragToReschedule(enabled) }
+    }
+
     /**
      * Switch the launcher label (#44). The card highlights at once, then settles
      * on what the component state reports; the writes are binder round-trips and

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/ViewsSettings.kt

@@ -114,7 +114,7 @@ internal fun ViewsScreen(
         GroupedRow(
             title = stringResource(R.string.settings_dim_completed),
             summary = stringResource(R.string.settings_dim_completed_summary),
-            position = Position.Bottom,
+            position = Position.Middle,
             trailing = {
                 Switch(
                     checked = state.dimCompletedEvents,
@@ -123,6 +123,18 @@ internal fun ViewsScreen(
             },
             onClick = { viewModel.setDimCompletedEvents(!state.dimCompletedEvents) },
         )
+        GroupedRow(
+            title = stringResource(R.string.settings_drag_to_reschedule),
+            summary = stringResource(R.string.settings_drag_to_reschedule_summary),
+            position = Position.Bottom,
+            trailing = {
+                Switch(
+                    checked = state.dragToReschedule,
+                    onCheckedChange = viewModel::setDragToReschedule,
+                )
+            },
+            onClick = { viewModel.setDragToReschedule(!state.dragToReschedule) },
+        )
 
         Spacer(Modifier.height(8.dp))
         SectionHeader(stringResource(R.string.settings_month_header))

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

@@ -439,6 +439,8 @@
     <string name="timeline_scale_custom_summary">The height you pinched the timeline to</string>
     <string name="settings_dim_completed">Dim completed events</string>
     <string name="settings_dim_completed_summary">Fade events that have already ended in month and week view</string>
+    <string name="settings_drag_to_reschedule">Drag to reschedule</string>
+    <string name="settings_drag_to_reschedule_summary">Move an event by dragging it to another day or time</string>
     <string name="settings_past_events">Past events</string>
     <string name="settings_past_events_show">Show</string>
     <string name="settings_past_events_dim">Dim</string>