Fix the Manage calendars way out and reformat the failure state (#304)

Opened from Settings, the backup screen has no calendar manager underneath,
so popping back landed on Settings. The action now opens the manager, which
is still a plain pop back when the manager is what opened the screen.

The failure state was one long string set as a headline. It now has a tonal
icon, a short headline and a supporting line, capped at a readable measure —
and the screen hands it an unscrolled column so it can actually centre.

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

@@ -550,10 +550,16 @@ fun CalendarHost(
             enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
             exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
         ) {
-            // The manager sits directly under this screen, so its failure states'
-            // "Manage calendars" way out is simply popping back to it (#304).
+            // Settings can open this screen without the manager underneath, so
+            // its failure states' "Manage calendars" way out has to open the
+            // manager rather than just pop — popping alone lands on Settings
+            // (#304). Coming from the manager the flag is already set, so this
+            // is the same pop-back there.
             CompositionLocalProvider(
-                LocalManageCalendars provides { showBackup = false },
+                LocalManageCalendars provides {
+                    showCalendars = true
+                    showBackup = false
+                },
             ) {
                 BackupScreen(
                     onBack = { showBackup = false },

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

@@ -8,6 +8,7 @@ import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
@@ -130,6 +131,10 @@ fun BackupScreen(
     CollapsingScaffold(
         title = stringResource(R.string.settings_section_backup),
         onBack = onBack,
+        // Loading and failure fill the screen and centre themselves, which they
+        // can only do in an unscrolled column — the scrolling one measures them
+        // against an unbounded height and leaves them hanging under the header.
+        scrollable = state is BackupUiState.Ready,
         snackbarHost = { SnackbarHost(snackbarHostState) },
         predictiveBack = true,
     ) {
@@ -172,13 +177,11 @@ fun BackupScreen(
     }
 }
 
-/** The screen's one-line loading state, in the scaffold's content column. */
+/** The screen's loading state, centred in the scaffold's content column. */
 @Composable
 private fun BackupLoading() {
     Box(
-        modifier = Modifier
-            .fillMaxWidth()
-            .padding(vertical = 48.dp),
+        modifier = Modifier.fillMaxSize(),
         contentAlignment = Alignment.Center,
     ) {
         CircularProgressIndicator()

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

@@ -4,19 +4,36 @@ import android.content.Context
 import android.content.Intent
 import android.provider.CalendarContract
 import android.provider.Settings
+import androidx.annotation.StringRes
+import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.widthIn
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.outlined.CalendarMonth
+import androidx.compose.material.icons.outlined.EditOff
+import androidx.compose.material.icons.outlined.ErrorOutline
+import androidx.compose.material.icons.outlined.EventBusy
+import androidx.compose.material.icons.outlined.Lock
+import androidx.compose.material.icons.outlined.SyncProblem
+import androidx.compose.material.icons.outlined.VisibilityOff
 import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.compositionLocalOf
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextAlign
@@ -26,28 +43,18 @@ import de.jeanlucmakiola.calendula.domain.FailureReason
 
 /**
  * Full-screen failure state shared by every calendar screen (spec §7).
- * One explanation line + one recovery action, never a toast.
+ * A tonal icon, one headline, one supporting line and one recovery action —
+ * never a toast.
  */
 @Composable
-fun CalendarFailure(reason: FailureReason, onRetry: () -> Unit) {
+fun CalendarFailure(
+    reason: FailureReason,
+    onRetry: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
     val context = LocalContext.current
     val manageCalendars = LocalManageCalendars.current
-    val titleRes = when (reason) {
-        FailureReason.PermissionRevoked -> R.string.state_failure_permission
-        FailureReason.NoCalendarsConfigured -> R.string.state_failure_no_calendars
-        FailureReason.AllCalendarsHidden -> R.string.state_failure_all_hidden
-        FailureReason.NoImportTarget -> R.string.state_failure_no_import_target
-        FailureReason.ProviderUnavailable -> R.string.state_failure_provider
-        FailureReason.Unknown,
-        FailureReason.EventNotFound -> R.string.state_failure_unknown
-    }
-    val actionRes = when (reason) {
-        FailureReason.NoCalendarsConfigured -> R.string.state_failure_no_calendars_action
-        FailureReason.AllCalendarsHidden -> R.string.state_failure_all_hidden_action
-        FailureReason.NoImportTarget -> R.string.state_failure_all_hidden_action
-        FailureReason.PermissionRevoked -> R.string.state_failure_permission_action
-        else -> R.string.state_retry
-    }
+    val copy = failureCopy(reason)
     val onAction: () -> Unit = when (reason) {
         FailureReason.NoCalendarsConfigured -> {
             { context.startCalendarSetup() }
@@ -58,24 +65,128 @@ fun CalendarFailure(reason: FailureReason, onRetry: () -> Unit) {
         else -> onRetry
     }
     Column(
-        modifier = Modifier
+        modifier = modifier
             .fillMaxSize()
-            .padding(32.dp),
+            .padding(horizontal = 32.dp, vertical = 24.dp),
         verticalArrangement = Arrangement.Center,
         horizontalAlignment = Alignment.CenterHorizontally,
     ) {
+        FailureIcon(icon = copy.icon, isError = copy.isError)
+        Spacer(Modifier.height(24.dp))
         Text(
-            text = stringResource(titleRes),
+            text = stringResource(copy.title),
             style = MaterialTheme.typography.headlineSmall,
             textAlign = TextAlign.Center,
+            modifier = Modifier.widthIn(max = TEXT_MAX_WIDTH),
         )
-        Spacer(Modifier.height(24.dp))
+        copy.body?.let { body ->
+            Spacer(Modifier.height(12.dp))
+            Text(
+                text = stringResource(body),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                textAlign = TextAlign.Center,
+                modifier = Modifier.widthIn(max = TEXT_MAX_WIDTH),
+            )
+        }
+        Spacer(Modifier.height(32.dp))
         FilledTonalButton(onClick = onAction) {
-            Text(stringResource(actionRes))
+            Text(stringResource(copy.action))
         }
     }
 }
 
+/** The state's mark: the reason's icon in a tonal circle above the headline. */
+@Composable
+private fun FailureIcon(icon: ImageVector, isError: Boolean) {
+    val container: Color
+    val content: Color
+    if (isError) {
+        container = MaterialTheme.colorScheme.errorContainer
+        content = MaterialTheme.colorScheme.onErrorContainer
+    } else {
+        container = MaterialTheme.colorScheme.secondaryContainer
+        content = MaterialTheme.colorScheme.onSecondaryContainer
+    }
+    Box(
+        modifier = Modifier
+            .size(72.dp)
+            .background(container, CircleShape),
+        contentAlignment = Alignment.Center,
+    ) {
+        Icon(
+            imageVector = icon,
+            contentDescription = null,
+            tint = content,
+            modifier = Modifier.size(36.dp),
+        )
+    }
+}
+
+/**
+ * What a reason says and offers. Headline and supporting line are separate so
+ * the explanation reads as body text instead of a headline that runs over three
+ * lines; [isError] tints the mark for the two reasons that are an actual fault
+ * rather than a calendar the user can switch back on.
+ */
+private data class FailureCopy(
+    val icon: ImageVector,
+    @StringRes val title: Int,
+    @StringRes val body: Int?,
+    @StringRes val action: Int,
+    val isError: Boolean = false,
+)
+
+private fun failureCopy(reason: FailureReason): FailureCopy = when (reason) {
+    FailureReason.PermissionRevoked -> FailureCopy(
+        icon = Icons.Outlined.Lock,
+        title = R.string.state_failure_permission,
+        body = R.string.state_failure_permission_body,
+        action = R.string.state_failure_permission_action,
+    )
+    FailureReason.NoCalendarsConfigured -> FailureCopy(
+        icon = Icons.Outlined.CalendarMonth,
+        title = R.string.state_failure_no_calendars,
+        body = R.string.state_failure_no_calendars_body,
+        action = R.string.state_failure_no_calendars_action,
+    )
+    FailureReason.AllCalendarsHidden -> FailureCopy(
+        icon = Icons.Outlined.VisibilityOff,
+        title = R.string.state_failure_all_hidden,
+        body = R.string.state_failure_all_hidden_body,
+        action = R.string.state_failure_all_hidden_action,
+    )
+    FailureReason.NoImportTarget -> FailureCopy(
+        icon = Icons.Outlined.EditOff,
+        title = R.string.state_failure_no_import_target,
+        body = R.string.state_failure_no_import_target_body,
+        action = R.string.state_failure_all_hidden_action,
+    )
+    FailureReason.EventNotFound -> FailureCopy(
+        icon = Icons.Outlined.EventBusy,
+        title = R.string.state_failure_event_not_found,
+        body = R.string.state_failure_event_not_found_body,
+        action = R.string.state_retry,
+    )
+    FailureReason.ProviderUnavailable -> FailureCopy(
+        icon = Icons.Outlined.SyncProblem,
+        title = R.string.state_failure_provider,
+        body = R.string.state_failure_provider_body,
+        action = R.string.state_retry,
+        isError = true,
+    )
+    FailureReason.Unknown -> FailureCopy(
+        icon = Icons.Outlined.ErrorOutline,
+        title = R.string.state_failure_unknown,
+        body = null,
+        action = R.string.state_retry,
+        isError = true,
+    )
+}
+
+/** Keeps the headline and its supporting line at a readable measure. */
+private val TEXT_MAX_WIDTH = 320.dp
+
 /**
  * Opens Settings → Calendars, the only screen that can switch a calendar back
  * on. Null outside the calendar host — screens without it never raise the

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailScreen.kt

@@ -302,6 +302,7 @@ fun EventDetailScreen(
             is EventDetailUiState.Failure -> CalendarFailure(
                 reason = s.reason,
                 onRetry = viewModel::retry,
+                modifier = contentModifier,
             )
             is EventDetailUiState.Success -> EventDetailContent(s, copyField, contentModifier)
         }

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

@@ -11,13 +11,20 @@
     <string name="state_retry">Retry</string>
     <string name="state_failure_unknown">Something went wrong.</string>
     <string name="state_failure_permission">Calendar access is required.</string>
+    <string name="state_failure_permission_body">Calendula reads your events straight from the system calendar, so it needs calendar access to show anything.</string>
     <string name="state_failure_permission_action">Grant access</string>
     <string name="state_failure_no_calendars">No calendars configured.</string>
+    <string name="state_failure_no_calendars_body">Add a calendar account to this device and its calendars show up here.</string>
     <string name="state_failure_no_calendars_action">Open system calendar settings</string>
     <string name="state_failure_all_hidden">All your calendars are switched off.</string>
+    <string name="state_failure_all_hidden_body">Switch at least one calendar back on to see its events.</string>
     <string name="state_failure_all_hidden_action">Manage calendars</string>
-    <string name="state_failure_no_import_target">None of your calendars can take new events. They are read-only, managed by another app, or not synced to this device.</string>
+    <string name="state_failure_no_import_target">No calendar can take new events.</string>
+    <string name="state_failure_no_import_target_body">The calendars that are switched on are read-only, managed by another app, or not synced to this device. Switch on a calendar that can take events, or add a local one.</string>
+    <string name="state_failure_event_not_found">This event is no longer there.</string>
+    <string name="state_failure_event_not_found_body">It may have been deleted, or moved to a calendar that is switched off.</string>
     <string name="state_failure_provider">Could not read the calendar.</string>
+    <string name="state_failure_provider_body">The system calendar did not answer. Try again in a moment.</string>
 
     <!-- Long-press a field to copy it (#195) -->
     <string name="field_copy_action">Copy</string>