Week numbers follow the device region, shared helper (#493)

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

@@ -0,0 +1,21 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import android.content.res.Resources
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import de.jeanlucmakiola.floret.time.rowWeekNumber
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.toJavaLocalDate
+import java.time.temporal.WeekFields
+
+/**
+ * The week number of the grid row starting on [rowStart], numbered by the
+ * device region's rules (#493). The region, not the app language: an English
+ * UI in the Netherlands still numbers weeks the ISO way. Shared by the Month
+ * gutter and the Week badge so the two always agree.
+ */
+@Composable
+internal fun rememberRowWeekNumber(rowStart: LocalDate): Int {
+    val fields = remember { WeekFields.of(Resources.getSystem().configuration.locales[0]) }
+    return remember(rowStart, fields) { rowStart.toJavaLocalDate().rowWeekNumber(fields) }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/month/MonthScreen.kt

@@ -187,7 +187,6 @@ import de.jeanlucmakiola.floret.identity.itemEnter
 import de.jeanlucmakiola.floret.identity.rememberReduceMotion
 import de.jeanlucmakiola.floret.locale.currentLocale
 import de.jeanlucmakiola.calendula.ui.common.next
-import de.jeanlucmakiola.floret.time.isoWeekNumber
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.filterNotNull
@@ -205,6 +204,7 @@ import java.time.format.TextStyle as JavaTextStyle
 import java.util.Locale
 import kotlinx.datetime.toJavaMonth
 import kotlinx.datetime.yearMonth
+import de.jeanlucmakiola.calendula.ui.common.rememberRowWeekNumber
 
 private val LocalTodayPulse = staticCompositionLocalOf { 0 }
 
@@ -2701,13 +2701,13 @@ private fun monthChipDragModifier(
 /**
  * Left-gutter calendar-week cell (#25): a full-height tonal pill mirroring the
  * day cells' geometry, set apart by the secondaryContainer tint (matching the
- * Week view's badge), with the ISO week number centred like a day number. The
- * week is computed on the row's first day — the same basis as the Week view — so
- * the two agree.
+ * Week view's badge), with the week number centred like a day number. It is
+ * numbered by the device region from the row's mid-week day, as in the Week
+ * view, so it is right for any first weekday (#493).
  */
 @Composable
 private fun WeekNumberGutter(weekStart: LocalDate, modifier: Modifier = Modifier) {
-    val weekNumber = remember(weekStart) { weekStart.toJavaLocalDate().isoWeekNumber() }
+    val weekNumber = rememberRowWeekNumber(weekStart)
     val label = stringResource(R.string.week_number_label)
     val openLabel = stringResource(R.string.month_open_week, weekNumber)
     val onOpenWeek = LocalOpenWeek.current

app/src/main/java/de/jeanlucmakiola/calendula/ui/week/WeekScreen.kt

@@ -209,7 +209,6 @@ import de.jeanlucmakiola.calendula.ui.common.TIMELINE_CONTENT_END_INSET
 import de.jeanlucmakiola.calendula.ui.common.hourCellBlockInset
 import de.jeanlucmakiola.calendula.ui.common.hourGridCells
 import de.jeanlucmakiola.calendula.ui.common.tappedMinuteOfDay
-import de.jeanlucmakiola.floret.time.isoWeekNumber
 import kotlinx.coroutines.launch
 import kotlinx.datetime.DateTimeUnit
 import kotlinx.datetime.LocalDate
@@ -221,6 +220,7 @@ import kotlinx.datetime.toLocalDateTime
 import java.time.format.TextStyle as JavaTextStyle
 import java.util.Locale
 import kotlinx.datetime.yearMonth
+import de.jeanlucmakiola.calendula.ui.common.rememberRowWeekNumber
 
 /** One lane of the all-day strip, sized to a trimmed bar line (#190). */
 private val ALL_DAY_ROW_HEIGHT = 20.dp
@@ -1137,7 +1137,7 @@ private fun WeekDayHeader(
  */
 @Composable
 private fun WeekNumberCell(weekStart: LocalDate, showBadge: Boolean, modifier: Modifier = Modifier) {
-    val weekNumber = remember(weekStart) { weekStart.toJavaLocalDate().isoWeekNumber() }
+    val weekNumber = rememberRowWeekNumber(weekStart)
     Column(
         modifier = modifier
             .fillMaxWidth()