Put the day view on the paged timeline (#184)

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

@@ -50,7 +50,7 @@ import de.jeanlucmakiola.calendula.ui.common.drillToDay
 import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
 import de.jeanlucmakiola.calendula.ui.common.selectView
 import de.jeanlucmakiola.calendula.ui.common.viewBaseStack
-import de.jeanlucmakiola.calendula.ui.day.DayScreen
+import de.jeanlucmakiola.calendula.ui.week.DayScreen
 import de.jeanlucmakiola.calendula.ui.detail.EventDetailScreen
 import de.jeanlucmakiola.calendula.ui.edit.EventEditScreen
 import de.jeanlucmakiola.calendula.ui.edit.ImportSource

app/src/main/java/de/jeanlucmakiola/calendula/ui/day/DayPaging.kt

@@ -1,22 +0,0 @@
-package de.jeanlucmakiola.calendula.ui.day
-
-import kotlinx.datetime.DateTimeUnit
-import kotlinx.datetime.LocalDate
-import kotlinx.datetime.daysUntil
-import kotlinx.datetime.plus
-
-/** Pages the day pager spans — a little under four centuries, centred on [PAGE_EPOCH]. */
-internal const val DAY_PAGE_COUNT: Int = 140_000
-
-private const val EPOCH_PAGE = DAY_PAGE_COUNT / 2
-
-/** The day at [EPOCH_PAGE]; any date works, it only has to stay fixed. */
-private val PAGE_EPOCH = LocalDate(2000, 1, 1)
-
-/** The day shown on pager [page]. */
-internal fun dayForPage(page: Int): LocalDate =
-    PAGE_EPOCH.plus(page - EPOCH_PAGE, DateTimeUnit.DAY)
-
-/** The pager page showing [date]. */
-internal fun dayPageFor(date: LocalDate): Int =
-    (EPOCH_PAGE + PAGE_EPOCH.daysUntil(date)).coerceIn(0, DAY_PAGE_COUNT - 1)

app/src/main/java/de/jeanlucmakiola/calendula/ui/day/DayUiState.kt

@@ -1,25 +0,0 @@
-package de.jeanlucmakiola.calendula.ui.day
-
-import de.jeanlucmakiola.calendula.domain.FailureReason
-import de.jeanlucmakiola.calendula.ui.week.AllDaySpan
-import de.jeanlucmakiola.calendula.ui.week.TimedBlock
-import kotlinx.datetime.LocalDate
-
-/**
- * The day view is a single-column slice of the week view (spec S3). It reuses the
- * week's [TimedBlock] and [AllDaySpan] layout primitives — for one day, all-day
- * spans collapse to a single column ([AllDaySpan.startCol] == [AllDaySpan.endCol]
- * == 0) and only their [AllDaySpan.lane] (vertical stacking) matters.
- */
-sealed interface DayUiState {
-    data object Loading : DayUiState
-    data class Failure(val reason: FailureReason) : DayUiState
-    data class Success(
-        val date: LocalDate,
-        val today: LocalDate,
-        /** All-day/multi-day events covering this day, stacked by lane. */
-        val allDay: List<AllDaySpan>,
-        /** Timed events clipped to this day with overlap lanes resolved. */
-        val timed: List<TimedBlock>,
-    ) : DayUiState
-}

app/src/main/java/de/jeanlucmakiola/calendula/ui/day/DayViewModel.kt

@@ -1,136 +0,0 @@
-package de.jeanlucmakiola.calendula.ui.day
-
-import androidx.lifecycle.ViewModel
-import androidx.lifecycle.viewModelScope
-import dagger.hilt.android.lifecycle.HiltViewModel
-import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
-import de.jeanlucmakiola.calendula.data.di.IoDispatcher
-import de.jeanlucmakiola.calendula.domain.CalendarSource
-import de.jeanlucmakiola.calendula.domain.EventInstance
-import de.jeanlucmakiola.calendula.domain.FailureReason
-import de.jeanlucmakiola.calendula.domain.calendarListFailure
-import de.jeanlucmakiola.calendula.ui.common.PageStateCache
-import de.jeanlucmakiola.calendula.ui.week.layoutAllDay
-import de.jeanlucmakiola.calendula.ui.week.layoutDay
-import kotlinx.coroutines.CoroutineDispatcher
-import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.SharingStarted
-import kotlinx.coroutines.flow.StateFlow
-import kotlinx.coroutines.flow.catch
-import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.filterNot
-import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.flowOn
-import kotlinx.coroutines.flow.map
-import kotlinx.coroutines.flow.stateIn
-import kotlinx.datetime.LocalDate
-import kotlinx.datetime.TimeZone
-import kotlinx.datetime.atStartOfDayIn
-import kotlinx.datetime.atTime
-import kotlinx.datetime.daysUntil
-import kotlinx.datetime.toInstant
-import kotlinx.datetime.toLocalDateTime
-import kotlin.time.Clock
-import kotlin.time.Instant
-import javax.inject.Inject
-import kotlin.math.abs
-
-/** How far from the requested day [DayViewModel.day] keeps other days cached. */
-private const val DAY_CACHE_DAYS = 7
-
-@OptIn(ExperimentalCoroutinesApi::class)
-@HiltViewModel
-class DayViewModel @Inject constructor(
-    private val repository: CalendarRepository,
-    @IoDispatcher private val io: CoroutineDispatcher,
-) : ViewModel() {
-
-    private val zone = TimeZone.currentSystemDefault()
-
-    private val todayDate: LocalDate
-        get() = Clock.System.now().toLocalDateTime(zone).date
-
-    private val _date = MutableStateFlow(todayDate)
-
-    /** The pager page the anchor day sits on. */
-    val anchorPage: StateFlow<Int> = _date
-        .map { dayPageFor(it) }
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5_000L),
-            initialValue = dayPageFor(todayDate),
-        )
-
-    /**
-     * The anchor day's state. Once loaded it never falls back to [DayUiState.Loading]:
-     * moving the anchor keeps the last result until the new day arrives, since
-     * the pages draw their own days and this only gates the failure screen.
-     */
-    val state: StateFlow<DayUiState> = _date
-        .flatMapLatest { date -> day(date).filterNot { it is DayUiState.Loading } }
-        .catch { emit(DayUiState.Failure(FailureReason.ProviderUnavailable)) }
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5_000L),
-            initialValue = DayUiState.Loading,
-        )
-
-    private val days = PageStateCache<LocalDate, DayUiState>(
-        scope = viewModelScope,
-        initial = DayUiState.Loading,
-        // Far enough to cover the pages either side and a swipe back, so paging
-        // through a month doesn't keep a month of queries around.
-        keep = { cached, requested -> abs(cached.daysUntil(requested)) <= DAY_CACHE_DAYS },
-    ) { date ->
-        combine(
-            repository.calendars(),
-            repository.instances(dayRange(date, zone)),
-        ) { calendars, instances ->
-            buildState(date, calendars, instances)
-        }
-            .catch { emit(DayUiState.Failure(FailureReason.ProviderUnavailable)) }
-            .flowOn(io)
-    }
-
-    /** The day [date], shared between its pager page and [state]. Main thread only. */
-    fun day(date: LocalDate): StateFlow<DayUiState> = days.get(date)
-
-    /** The pager came to rest on [page]; follow it unless it is already the anchor's. */
-    fun onPageSettled(page: Int) {
-        if (dayPageFor(_date.value) != page) _date.value = dayForPage(page)
-    }
-
-    fun goToToday() {
-        _date.value = todayDate
-    }
-
-    /** Jump to a specific date (e.g. when opened from the month grid). */
-    fun goToDate(date: LocalDate) {
-        _date.value = date
-    }
-
-    private fun buildState(
-        day: LocalDate,
-        calendars: List<CalendarSource>,
-        instances: List<EventInstance>,
-    ): DayUiState {
-        calendarListFailure(calendars)?.let { return DayUiState.Failure(it) }
-        val days = listOf(day)
-        val allDay = instances.filter { it.isAllDay }
-        val timed = instances.filterNot { it.isAllDay }
-        return DayUiState.Success(
-            date = day,
-            today = todayDate,
-            allDay = layoutAllDay(allDay, days, zone),
-            timed = layoutDay(timed, day, zone),
-        )
-    }
-}
-
-/** Half-open instant range covering the single calendar [date]. */
-internal fun dayRange(date: LocalDate, zone: TimeZone): ClosedRange<Instant> {
-    val from = date.atStartOfDayIn(zone)
-    val to = date.atTime(23, 59, 59).toInstant(zone)
-    return from..to
-}

app/src/main/java/de/jeanlucmakiola/calendula/ui/day/DayViewPreview.kt

@@ -1,63 +0,0 @@
-package de.jeanlucmakiola.calendula.ui.day
-
-import androidx.compose.foundation.rememberScrollState
-import androidx.compose.runtime.Composable
-import androidx.compose.runtime.LaunchedEffect
-import androidx.compose.runtime.remember
-import androidx.compose.runtime.snapshotFlow
-import androidx.compose.ui.Modifier
-import androidx.compose.ui.unit.Dp
-import de.jeanlucmakiola.calendula.ui.common.ScaledViewPreview
-import de.jeanlucmakiola.calendula.ui.common.rememberTimelineDragController
-import de.jeanlucmakiola.calendula.ui.common.sampleTimelineEvents
-import de.jeanlucmakiola.calendula.ui.week.layoutAllDay
-import de.jeanlucmakiola.calendula.ui.week.layoutDay
-import kotlinx.coroutines.flow.first
-import kotlinx.datetime.LocalDate
-import kotlinx.datetime.TimeZone
-import kotlinx.datetime.toLocalDateTime
-import kotlin.time.Clock
-
-/**
- * A live, scaled-down Day view for the onboarding view chooser. Today's date is
- * real; only the events are stand-ins.
- */
-@Composable
-internal fun DayViewPreview(
-    height: Dp,
-    modifier: Modifier = Modifier,
-) {
-    val zone = remember { TimeZone.currentSystemDefault() }
-    val today = remember(zone) { Clock.System.now().toLocalDateTime(zone).date }
-    val state = remember(today, zone) { sampleDayState(today, zone) }
-    val scrollState = rememberScrollState()
-    LaunchedEffect(Unit) {
-        snapshotFlow { scrollState.maxValue }.first { it > 0 }
-        // Half the scroll range is noon — the same centring the live view does.
-        scrollState.scrollTo(scrollState.maxValue / 2)
-    }
-
-    ScaledViewPreview(height = height, modifier = modifier) {
-        DaySuccess(
-            state = state,
-            scrollState = scrollState,
-            allDayHeight = state.allDayStripHeight(),
-            dragController = rememberTimelineDragController(),
-            onEventClick = {},
-            onCreateAt = { _, _ -> },
-            onDrop = {},
-        )
-    }
-}
-
-/** Sample day state, laid out through the same helpers the live view uses. */
-private fun sampleDayState(today: LocalDate, zone: TimeZone): DayUiState.Success {
-    val days = listOf(today)
-    val events = sampleTimelineEvents(days, today, zone)
-    return DayUiState.Success(
-        date = today,
-        today = today,
-        allDay = layoutAllDay(events.filter { it.isAllDay }, days, zone),
-        timed = layoutDay(events, today, zone),
-    )
-}

app/src/main/java/de/jeanlucmakiola/calendula/ui/onboarding/ViewStep.kt

@@ -23,7 +23,6 @@ import de.jeanlucmakiola.calendula.ui.common.PickerDescription
 import de.jeanlucmakiola.calendula.ui.common.ViewPreviewFrame
 import de.jeanlucmakiola.calendula.ui.common.icon
 import de.jeanlucmakiola.calendula.ui.common.label
-import de.jeanlucmakiola.calendula.ui.day.DayViewPreview
 import de.jeanlucmakiola.calendula.ui.month.MonthStylePreview
 import de.jeanlucmakiola.calendula.ui.month.MonthViewStyle
 import de.jeanlucmakiola.calendula.ui.month.descriptionRes
@@ -73,7 +72,7 @@ internal fun ViewStep(
                     height = PREVIEW_HEIGHT,
                     dayCount = LocalMultiDayCount.current,
                 )
-                CalendarView.Day -> DayViewPreview(height = PREVIEW_HEIGHT)
+                CalendarView.Day -> WeekViewPreview(weekStart = weekStart, height = PREVIEW_HEIGHT, dayCount = 1)
                 CalendarView.Agenda -> AgendaViewPreview(height = PREVIEW_HEIGHT)
             }
         }

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

@@ -73,3 +73,23 @@ data class DaysGrid(override val dayCount: Int, val phase: Int) : PageGrid {
             DaysGrid(dayCount, Math.floorMod(DAYS_EPOCH.daysUntil(date), dayCount))
     }
 }
+
+/** Pages the day pager spans — a little under four centuries, centred on [DAY_EPOCH]. */
+internal const val DAY_PAGE_COUNT: Int = 140_000
+
+private const val DAY_EPOCH_PAGE = DAY_PAGE_COUNT / 2
+
+/** The day at [DAY_EPOCH_PAGE]; any date works, it only has to stay fixed. */
+private val DAY_EPOCH = LocalDate(2000, 1, 1)
+
+/** Single days: every date starts a page of its own. */
+data object DayGrid : PageGrid {
+    override val dayCount: Int get() = 1
+    override val pageCount: Int get() = DAY_PAGE_COUNT
+
+    override fun startForPage(page: Int): LocalDate =
+        DAY_EPOCH.plus(page - DAY_EPOCH_PAGE, DateTimeUnit.DAY)
+
+    override fun pageFor(date: LocalDate): Int =
+        (DAY_EPOCH_PAGE + DAY_EPOCH.daysUntil(date)).coerceIn(0, DAY_PAGE_COUNT - 1)
+}

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

@@ -66,6 +66,7 @@ import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
+import androidx.compose.ui.BiasAlignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.draw.clip
@@ -184,6 +185,9 @@ private val HEADER_BOTTOM_PADDING = 8.dp
 /** The header's date slot, reserved whether or not it holds today's circle. */
 private val DATE_SLOT_SIZE = 28.dp
 
+/** A start-aligned header cell's inset, lining its date up with the event titles below. */
+private val HEADER_START_INSET = BLOCK_OUTER_INSET + BLOCK_TEXT_PADDING
+
 /** The weekday header's height, which the day view takes off to fit the week's hours (#184). */
 @Composable
 internal fun weekDayHeaderHeight(): Dp {
@@ -216,7 +220,7 @@ fun WeekScreen(
     viewModel: WeekViewModel = hiltViewModel(),
 ) = PagedTimelineScreen(
     viewModel = viewModel,
-    showWeekNumber = true,
+    kind = TimelineKind.Week,
     selectedView = selectedView,
     onSelectView = onSelectView,
     onOpenDay = onOpenDay,
@@ -247,8 +251,7 @@ fun MultiDayScreen(
     viewModel: MultiDayViewModel = hiltViewModel(),
 ) = PagedTimelineScreen(
     viewModel = viewModel,
-    // A run of days often straddles two weeks, so no single number fits it.
-    showWeekNumber = false,
+    kind = TimelineKind.MultiDay,
     selectedView = selectedView,
     onSelectView = onSelectView,
     onOpenDay = onOpenDay,
@@ -262,11 +265,66 @@ fun MultiDayScreen(
     modifier = modifier,
 )
 
+/** The day view: the week view's timeline one day at a time. */
+@Composable
+fun DayScreen(
+    selectedView: CalendarView,
+    onSelectView: (CalendarView) -> Unit,
+    onEventClick: (EventInstance) -> Unit,
+    onOpenSettings: () -> Unit,
+    onOpenSearch: () -> Unit,
+    onCreateEvent: (LocalDate, Int?) -> Unit,
+    quickSwitchViews: List<CalendarView> = IMPLEMENTED_VIEWS,
+    drawerViewOrder: List<CalendarView> = IMPLEMENTED_VIEWS,
+    todayInToolbar: Boolean = false,
+    modifier: Modifier = Modifier,
+    initialDateIso: String? = null,
+    viewModel: DayViewModel = hiltViewModel(),
+) = PagedTimelineScreen(
+    viewModel = viewModel,
+    kind = TimelineKind.Day,
+    selectedView = selectedView,
+    onSelectView = onSelectView,
+    // Tapping the one column's header would only reopen this day.
+    onOpenDay = {},
+    onEventClick = onEventClick,
+    onOpenSettings = onOpenSettings,
+    onOpenSearch = onOpenSearch,
+    onCreateEvent = onCreateEvent,
+    quickSwitchViews = quickSwitchViews,
+    drawerViewOrder = drawerViewOrder,
+    todayInToolbar = todayInToolbar,
+    modifier = modifier,
+    initialDate = initialDateIso?.let(LocalDate::parse),
+)
+
+/** What sets the timeline views apart; everything else they share. */
+internal enum class TimelineKind(
+    val showWeekNumber: Boolean,
+    val todayText: Int,
+    /** Where a header cell sits in its column: centred, or at the start like the event titles. */
+    val headerBias: Float,
+) {
+    Week(showWeekNumber = true, todayText = R.string.week_today_action, headerBias = 0f),
+
+    // A run of days often straddles two weeks, so no single number fits it.
+    MultiDay(showWeekNumber = false, todayText = R.string.week_today_action, headerBias = 0f),
+    Day(showWeekNumber = false, todayText = R.string.day_today_action, headerBias = -1f),
+    ;
+
+    fun title(start: LocalDate, end: LocalDate, locale: Locale, currentYear: Int, abbreviated: Boolean): String =
+        if (this == Day) {
+            formatDayTitle(start, locale, currentYear, abbreviated)
+        } else {
+            formatWeekTitle(start, end, locale, currentYear, abbreviated)
+        }
+}
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 private fun PagedTimelineScreen(
     viewModel: PagedTimelineViewModel,
-    showWeekNumber: Boolean,
+    kind: TimelineKind,
     selectedView: CalendarView,
     onSelectView: (CalendarView) -> Unit,
     onOpenDay: (LocalDate) -> Unit,
@@ -278,7 +336,9 @@ private fun PagedTimelineScreen(
     drawerViewOrder: List<CalendarView>,
     todayInToolbar: Boolean,
     modifier: Modifier,
+    initialDate: LocalDate? = null,
 ) {
+    LaunchedEffect(initialDate) { initialDate?.let(viewModel::jumpTo) }
     val state by viewModel.state.collectAsStateWithLifecycle()
     val position by viewModel.position.collectAsStateWithLifecycle()
     val grid = position.grid
@@ -368,6 +428,7 @@ private fun PagedTimelineScreen(
             modifier = modifier,
             topBar = {
                 WeekTopBar(
+                    kind = kind,
                     weekStart = weekStart,
                     weekEnd = weekEnd,
                     currentYear = today.year,
@@ -384,7 +445,7 @@ private fun PagedTimelineScreen(
             floatingActionButton = {
                 CalendarFabColumn(
                     todayVisible = !isOnCurrentWeek && !todayInToolbar,
-                    todayText = stringResource(R.string.week_today_action),
+                    todayText = stringResource(kind.todayText),
                     onToday = jumpToToday,
                     onCreate = {
                         // Anchor on today when it's in view, else the week's first day.
@@ -398,7 +459,7 @@ private fun PagedTimelineScreen(
                     state = state,
                     pagerState = pagerState,
                     grid = grid,
-                    showWeekNumber = showWeekNumber,
+                    kind = kind,
                     span = viewModel::span,
                     onRetry = viewModel::goToToday,
                     onEventClick = onEventClick,
@@ -418,7 +479,7 @@ private fun WeekContent(
     state: WeekUiState,
     pagerState: PagerState,
     grid: PageGrid,
-    showWeekNumber: Boolean,
+    kind: TimelineKind,
     span: (DaySpan) -> StateFlow<WeekUiState>,
     onRetry: () -> Unit,
     onEventClick: (EventInstance) -> Unit,
@@ -466,7 +527,7 @@ private fun WeekContent(
                 is WeekUiState.Success -> WeekPager(
                     pagerState = pagerState,
                     grid = grid,
-                    showWeekNumber = showWeekNumber,
+                    kind = kind,
                     span = span,
                     today = s.today,
                     initialStripHeight = s.allDayStripHeight(),
@@ -491,7 +552,7 @@ private fun WeekContent(
 private fun WeekPager(
     pagerState: PagerState,
     grid: PageGrid,
-    showWeekNumber: Boolean,
+    kind: TimelineKind,
     span: (DaySpan) -> StateFlow<WeekUiState>,
     today: LocalDate,
     initialStripHeight: Dp,
@@ -506,7 +567,7 @@ private fun WeekPager(
     val allDayHeight = pagedHeight(pagerState, stripHeights, initialStripHeight)
     WeekFrame(
         weekStart = grid.startForPage(pagerState.currentPage),
-        showWeekNumber = showWeekNumber,
+        showWeekNumber = kind.showWeekNumber,
         allDayHeight = allDayHeight,
         scrollState = scrollState,
         dragController = dragController,
@@ -537,6 +598,7 @@ private fun WeekPager(
             ViewMorphPage(active = morphPageActive(page, pagerState.settledPage)) {
                 WeekPage(
                     state = loaded ?: empty,
+                    headerBias = kind.headerBias,
                     allDayHeight = allDayHeight,
                     scrollState = scrollState,
                     dragController = dragController,
@@ -610,6 +672,7 @@ private fun WeekFrame(
 internal fun WeekSuccess(
     state: WeekUiState.Success,
     showWeekNumber: Boolean = true,
+    headerBias: Float = 0f,
     scrollState: ScrollState,
     allDayHeight: Dp,
     dragController: TimelineDragController,
@@ -627,6 +690,7 @@ internal fun WeekSuccess(
     ) {
         WeekPage(
             state = state,
+            headerBias = headerBias,
             allDayHeight = allDayHeight,
             scrollState = scrollState,
             dragController = dragController,
@@ -648,6 +712,7 @@ internal fun WeekSuccess(
 @Composable
 private fun WeekPage(
     state: WeekUiState.Success,
+    headerBias: Float,
     allDayHeight: Dp,
     scrollState: ScrollState,
     dragController: TimelineDragController,
@@ -663,7 +728,7 @@ private fun WeekPage(
                 .fillMaxWidth()
                 .background(MaterialTheme.colorScheme.surface),
         ) {
-            WeekDayHeader(days = state.days, today = state.today, onOpenDay = onOpenDay)
+            WeekDayHeader(days = state.days, today = state.today, bias = headerBias, onOpenDay = onOpenDay)
             // This strip is painted on `surface`, so an outlined chip has to
             // fill with that and not with the columns' container (#230).
             CompositionLocalProvider(
@@ -689,6 +754,7 @@ private fun WeekPage(
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 private fun WeekTopBar(
+    kind: TimelineKind,
     weekStart: LocalDate,
     weekEnd: LocalDate,
     currentYear: Int,
@@ -702,9 +768,9 @@ private fun WeekTopBar(
     onToday: () -> Unit,
 ) {
     val locale = currentLocale()
-    val (title, shortTitle) = remember(weekStart, weekEnd, locale, currentYear) {
-        formatWeekTitle(weekStart, weekEnd, locale, currentYear) to
-            formatWeekTitle(weekStart, weekEnd, locale, currentYear, abbreviated = true)
+    val (title, shortTitle) = remember(kind, weekStart, weekEnd, locale, currentYear) {
+        kind.title(weekStart, weekEnd, locale, currentYear, abbreviated = false) to
+            kind.title(weekStart, weekEnd, locale, currentYear, abbreviated = true)
     }
     TopAppBar(
         title = {
@@ -751,6 +817,7 @@ private fun WeekTopBar(
 private fun WeekDayHeader(
     days: List<LocalDate>,
     today: LocalDate,
+    bias: Float,
     onOpenDay: (LocalDate) -> Unit,
 ) {
     val locale = currentLocale()
@@ -766,8 +833,9 @@ private fun WeekDayHeader(
                 modifier = Modifier
                     .weight(1f)
                     .clip(RoundedCornerShape(12.dp))
-                    .clickable { onOpenDay(date) },
-                horizontalAlignment = Alignment.CenterHorizontally,
+                    .clickable { onOpenDay(date) }
+                    .padding(start = HEADER_START_INSET * -bias),
+                horizontalAlignment = BiasAlignment.Horizontal(bias),
             ) {
                 // One line, as the gutter cell beside it assumes (see WeekNumberCell).
                 Text(
@@ -1384,3 +1452,17 @@ private fun formatWeekTitle(
         forceYear = weekEnd.year != weekStart.year,
     )
 }
+
+/** The day's title: its weekday and date, abbreviated to the date alone when short of room. */
+private fun formatDayTitle(
+    date: LocalDate,
+    locale: Locale,
+    currentYear: Int,
+    abbreviated: Boolean = false,
+): String =
+    formatCalendarTitle(
+        date = java.time.LocalDate.of(date.year, date.month.ordinal + 1, date.day),
+        locale = locale,
+        currentYear = currentYear,
+        skeleton = if (abbreviated) "dMMM" else "EEEdMMM",
+    )

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

@@ -24,6 +24,7 @@ import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.filterNot
 import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
@@ -208,6 +209,20 @@ class MultiDayViewModel @Inject constructor(
     initialRule = { DaysGrid.startingAt(it, SettingsPrefs.DEFAULT_MULTI_DAY_COUNT) },
 )
 
+/** The day view: the timeline one day at a time. */
+@HiltViewModel
+class DayViewModel @Inject constructor(
+    repository: CalendarRepository,
+    settingsPrefs: SettingsPrefs,
+    @IoDispatcher io: CoroutineDispatcher,
+) : PagedTimelineViewModel(
+    repository = repository,
+    settingsPrefs = settingsPrefs,
+    io = io,
+    gridRule = flowOf { _: LocalDate -> DayGrid },
+    initialRule = { DayGrid },
+)
+
 /**
  * Lay out all-day events as connected horizontal spans across the visible week.
  * Each event becomes one [AllDaySpan] from its first to its last covered column;

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

@@ -50,6 +50,7 @@ internal fun WeekViewPreview(
         WeekSuccess(
             state = state,
             showWeekNumber = dayCount == 7,
+            headerBias = if (dayCount == 1) TimelineKind.Day.headerBias else 0f,
             scrollState = scrollState,
             allDayHeight = state.allDayStripHeight(),
             dragController = rememberTimelineDragController(),

app/src/test/java/de/jeanlucmakiola/calendula/ui/day/DayPagingTest.kt

@@ -1,22 +0,0 @@
-package de.jeanlucmakiola.calendula.ui.day
-
-import com.google.common.truth.Truth.assertThat
-import kotlinx.datetime.LocalDate
-import org.junit.jupiter.api.Test
-
-class DayPagingTest {
-
-    @Test
-    fun `a page and its day round-trip`() {
-        listOf(LocalDate(2026, 9, 27), LocalDate(1990, 5, 16), LocalDate(2100, 2, 28)).forEach { day ->
-            assertThat(dayForPage(dayPageFor(day))).isEqualTo(day)
-        }
-    }
-
-    @Test
-    fun `adjacent pages are adjacent days across a month end`() {
-        val page = dayPageFor(LocalDate(2026, 2, 28))
-        assertThat(dayForPage(page + 1)).isEqualTo(LocalDate(2026, 3, 1))
-        assertThat(dayForPage(page - 1)).isEqualTo(LocalDate(2026, 2, 27))
-    }
-}

app/src/test/java/de/jeanlucmakiola/calendula/ui/week/WeekPagingTest.kt

@@ -64,4 +64,18 @@ class WeekPagingTest {
         assertThat(grid.startForPage(page)).isEqualTo(date)
         assertThat(grid.startForPage(page - 1)).isEqualTo(LocalDate(1990, 5, 13))
     }
+
+    @Test
+    fun `a day page and its day round-trip`() {
+        listOf(LocalDate(2026, 9, 27), LocalDate(1990, 5, 16), LocalDate(2100, 2, 28)).forEach { day ->
+            assertThat(DayGrid.startForPage(DayGrid.pageFor(day))).isEqualTo(day)
+        }
+    }
+
+    @Test
+    fun `adjacent day pages are adjacent days across a month end`() {
+        val page = DayGrid.pageFor(LocalDate(2026, 2, 28))
+        assertThat(DayGrid.startForPage(page + 1)).isEqualTo(LocalDate(2026, 3, 1))
+        assertThat(DayGrid.startForPage(page - 1)).isEqualTo(LocalDate(2026, 2, 27))
+    }
 }