List the open-source projects Calendula ships (#284)

Adds a Settings entry listing the open-source projects Calendula ships, with copyright holder, SPDX licence id and a tap-through to each project's source. Apache-2.0 §4(a)/§4(d) are discharged by what the recipient of the APK is shown, not by a notice in the repository.

New `ui/licences/` package mirroring Agendula's:

- `OpenSourceLicences.kt` — `Attribution(name, copyright, licence, sourceUrl)` list plus a `Licence` enum (SPDX id + licence URL). Hand-maintained; the KDoc says why, and that adding a dependency means adding it here.
- `LicencesScreen.kt` — `CollapsingScaffold` + one `GroupedRow` per entry, summary `<copyright> · <SPDX id>`, tapping a row opens that project's source.

Reached from a new row in the **About** group in `SettingsScreen.kt`, before the privacy row so the group still ends on privacy. It uses `Icons.Default.Code`, since Gavel already belongs to the app's own License row.

Entries cover everything with `implementation` scope: AndroidX/Compose/Glance/WorkManager/DataStore/DocumentFile, Kotlin and kotlinx, Dagger and Hilt, Material Design icons, and floret-kit (MIT). Test-only dependencies are not shipped and stay off the list. Strings live in `values/strings.xml`.

Deviation from the issue: the footer text differs from Agendula's. Agendula's says every change to vendored code is listed in the linked repository — Calendula modifies nothing it ships, so the footer states that instead.

Closes #281

Co-authored-by: Jean-Luc Makiola <business@jeanlucmakiola.de>
Reviewed-on: https://codeberg.org/jlmakiola/calendula/pulls/284

app/src/main/java/de/jeanlucmakiola/calendula/ui/licences/LicencesScreen.kt

@@ -0,0 +1,60 @@
+package de.jeanlucmakiola.calendula.ui.licences
+
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalUriHandler
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.floret.components.CollapsingScaffold
+import de.jeanlucmakiola.floret.components.GroupedListInset
+import de.jeanlucmakiola.floret.components.GroupedRow
+import de.jeanlucmakiola.floret.components.positionOf
+
+/**
+ * Third-party attribution.
+ *
+ * Reachable from Settings rather than buried, because Apache-2.0 §4(a) is about
+ * what the *recipient of the binary* is told. Each row opens the project's source.
+ */
+@Composable
+internal fun LicencesScreen(onBack: () -> Unit) {
+    val uriHandler = LocalUriHandler.current
+
+    CollapsingScaffold(
+        title = stringResource(R.string.licences_title),
+        onBack = onBack,
+        predictiveBack = true,
+    ) {
+        Text(
+            stringResource(R.string.licences_intro),
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+            modifier = Modifier.padding(horizontal = GroupedListInset),
+        )
+        Spacer(Modifier.height(16.dp))
+
+        OpenSourceLicences.ALL.forEachIndexed { index, attribution ->
+            GroupedRow(
+                title = attribution.name,
+                summary = "${attribution.copyright} · ${attribution.licence.spdxId}",
+                position = positionOf(index, OpenSourceLicences.ALL.size),
+                onClick = { uriHandler.openUri(attribution.sourceUrl) },
+            )
+        }
+
+        Spacer(Modifier.height(24.dp))
+        Text(
+            stringResource(R.string.licences_footer),
+            style = MaterialTheme.typography.bodySmall,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+            modifier = Modifier.padding(horizontal = GroupedListInset),
+        )
+        Spacer(Modifier.height(24.dp))
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/licences/OpenSourceLicences.kt

@@ -0,0 +1,68 @@
+package de.jeanlucmakiola.calendula.ui.licences
+
+/**
+ * The third-party code Calendula ships, and what each licence obliges us to say.
+ *
+ * This screen is a **licence obligation, not an about-page nicety**:
+ * **Apache-2.0 §4(a)** requires the licence to travel with the work and **§4(d)**
+ * propagates any `NOTICE` file. What discharges that is what the recipient of the
+ * APK is shown — a notice only visible to someone reading the repository does not
+ * count. Nearly everything below is Apache-2.0.
+ *
+ * Hand-maintained on purpose. Generators read POM metadata, and POM metadata is
+ * routinely wrong — the licence name is often not an SPDX id and the licence URL
+ * frequently 404s, which produces confidently incomplete output. A short honest
+ * list beats a long generated one that omits the entry that mattered.
+ *
+ * **When adding a dependency, add it here.** There is no automated check that can
+ * tell you that you forgot. Test-only dependencies (JUnit, Truth, Turbine) are not
+ * shipped in the APK and stay off the list.
+ */
+data class Attribution(
+    val name: String,
+    val copyright: String,
+    val licence: Licence,
+    /** Where the source can actually be obtained; what each row links to. */
+    val sourceUrl: String,
+)
+
+enum class Licence(val spdxId: String, val url: String) {
+    APACHE_2("Apache-2.0", "https://www.apache.org/licenses/LICENSE-2.0"),
+    MIT("MIT", "https://opensource.org/license/mit"),
+}
+
+object OpenSourceLicences {
+
+    val ALL: List<Attribution> = listOf(
+        Attribution(
+            name = "AndroidX, Jetpack Compose, Glance, WorkManager, DataStore, DocumentFile",
+            copyright = "© The Android Open Source Project",
+            licence = Licence.APACHE_2,
+            sourceUrl = "https://cs.android.com/androidx/platform/frameworks/support",
+        ),
+        Attribution(
+            name = "Kotlin, kotlinx.coroutines, kotlinx.datetime",
+            copyright = "© JetBrains s.r.o. and Kotlin Programming Language contributors",
+            licence = Licence.APACHE_2,
+            sourceUrl = "https://github.com/JetBrains/kotlin",
+        ),
+        Attribution(
+            name = "Dagger and Hilt",
+            copyright = "© Google LLC and The Dagger Authors",
+            licence = Licence.APACHE_2,
+            sourceUrl = "https://github.com/google/dagger",
+        ),
+        Attribution(
+            name = "Material Design icons",
+            copyright = "© Google LLC",
+            licence = Licence.APACHE_2,
+            sourceUrl = "https://github.com/google/material-design-icons",
+        ),
+        Attribution(
+            name = "floret-kit",
+            copyright = "© Jean-Luc Makiola",
+            licence = Licence.MIT,
+            sourceUrl = "https://codeberg.org/jlmakiola/floret-kit",
+        ),
+    )
+}

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

@@ -21,6 +21,7 @@ import androidx.compose.material.icons.filled.Backup
 import androidx.compose.material.icons.filled.BugReport
 import androidx.compose.material.icons.filled.Cake
 import androidx.compose.material.icons.filled.CalendarMonth
+import androidx.compose.material.icons.filled.Code
 import androidx.compose.material.icons.filled.Favorite
 import androidx.compose.material.icons.filled.Gavel
 import androidx.compose.material.icons.filled.Language
@@ -54,6 +55,7 @@ import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import de.jeanlucmakiola.calendula.R
 import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
+import de.jeanlucmakiola.calendula.ui.licences.LicencesScreen
 import de.jeanlucmakiola.floret.components.AboutCard
 import de.jeanlucmakiola.floret.components.CollapsingScaffold
 import de.jeanlucmakiola.floret.components.GroupedListInset
@@ -67,7 +69,9 @@ import de.jeanlucmakiola.floret.crash.submitCrashReport
 import de.jeanlucmakiola.floret.locale.AppLanguage
 
 /** The settings sub-screens reached from the hub's category rows. */
-private enum class SettingsSection { Appearance, Views, EventForm, Notifications, SpecialDates, Widgets }
+private enum class SettingsSection {
+    Appearance, Views, EventForm, Notifications, SpecialDates, Widgets, Licences
+}
 
 /**
  * Settings hub: three labelled groups of category rows, each opening a
@@ -146,6 +150,13 @@ fun SettingsScreen(
         ) {
             WidgetsScreen(state = state, viewModel = viewModel, onBack = { section = null })
         }
+        AnimatedVisibility(
+            visible = section == SettingsSection.Licences,
+            enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
+            exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
+        ) {
+            LicencesScreen(onBack = { section = null })
+        }
     }
 }
 
@@ -253,6 +264,13 @@ private fun SettingsHub(
             icon = Icons.Default.Gavel,
             position = Position.Middle,
         )
+        GroupedRow(
+            title = stringResource(R.string.settings_licences),
+            summary = stringResource(R.string.settings_licences_subtitle),
+            position = Position.Middle,
+            leading = { CategoryIcon(Icons.Default.Code, ChipAccent.Neutral) },
+            onClick = { onOpenSection(SettingsSection.Licences) },
+        )
         AboutLinkRow(
             label = stringResource(R.string.settings_about_privacy),
             url = stringResource(R.string.about_privacy_url),

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

@@ -620,6 +620,8 @@
     <string name="settings_license_value">MIT</string>
     <string name="settings_about_author">by Jean-Luc Makiola</string>
     <string name="settings_about_source">Source</string>
+    <string name="settings_licences">Open source licenses</string>
+    <string name="settings_licences_subtitle">The projects Calendula is built on</string>
     <string name="settings_about_privacy">Privacy policy</string>
     <string name="settings_about_support">Support development</string>
     <string name="settings_about_version">Version %1$s</string>
@@ -627,6 +629,11 @@
     <string name="settings_report_problem">Report a problem</string>
     <string name="settings_report_problem_hint">Send a crash report or open the issue tracker</string>
 
+    <!-- Open source licences -->
+    <string name="licences_title">Open source licenses</string>
+    <string name="licences_intro">Calendula includes the work below. Tap any entry to get its source code.</string>
+    <string name="licences_footer">Every project here is included unmodified, under the license shown.</string>
+
     <!-- Calendar manager -->
     <string name="calendars_title">Calendars</string>
     <string name="calendars_local_header">Your calendars</string>