.gitea/workflows/translations.yaml

@@ -0,0 +1,41 @@
+name: Translations
+
+# Fast, SDK-free parity check for translation resources, so Weblate PRs (which
+# only touch values-*/strings.xml) get quick feedback without the full Android
+# build. The deeper checks still run in CI via lintDebug (ExtraTranslation).
+on:
+  push:
+    branches:
+      - '**'
+    tags-ignore:
+      - '**'
+    paths:
+      - 'app/src/main/res/values*/strings.xml'
+      - 'app/src/main/res/xml/locales_config.xml'
+      - 'scripts/check_translations.py'
+      - '.gitea/workflows/translations.yaml'
+
+concurrency:
+  group: translations-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: docker
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Ensure python3
+        run: |
+          if ! command -v python3 >/dev/null 2>&1; then
+            if command -v apt-get >/dev/null 2>&1; then
+              apt-get update && apt-get install -y python3
+            elif command -v apk >/dev/null 2>&1; then
+              apk add --no-cache python3
+            fi
+          fi
+          python3 --version
+
+      - name: Check translation parity
+        run: python3 scripts/check_translations.py

app/build.gradle.kts

@@ -78,6 +78,15 @@ android {
         }
     }
 
+    lint {
+        // Community translations are expected to be partial — a missing string
+        // falls back to the English base at runtime — so don't fail the build on
+        // it. Stale/extra keys (ExtraTranslation) stay fatal; scripts/
+        // check_translations.py guards the same invariants with clearer,
+        // translator-facing messages.
+        informational += "MissingTranslation"
+    }
+
     testOptions {
         unitTests {
             all { it.useJUnitPlatform() }

app/src/main/AndroidManifest.xml

@@ -32,6 +32,7 @@
         android:fullBackupContent="@xml/backup_rules"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
+        android:localeConfig="@xml/locales_config"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Calendula"

app/src/main/java/de/jeanlucmakiola/calendula/MainActivity.kt

@@ -3,9 +3,9 @@ package de.jeanlucmakiola.calendula
 import android.content.Context
 import android.content.Intent
 import android.os.Bundle
-import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.appcompat.app.AppCompatActivity
 import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.getValue
@@ -24,7 +24,7 @@ import de.jeanlucmakiola.calendula.ui.theme.CalendulaTheme
 import kotlinx.datetime.LocalDate
 
 @AndroidEntryPoint
-class MainActivity : ComponentActivity() {
+class MainActivity : AppCompatActivity() {
 
     // The occurrence a reminder notification was tapped for (eventId, begin,
     // end — the detail screen's key shape). singleTop + onNewIntent route a

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

@@ -1,36 +1,78 @@
 package de.jeanlucmakiola.calendula.ui.settings
 
+import android.content.Context
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.core.os.LocaleListCompat
+import de.jeanlucmakiola.calendula.R
+import org.xmlpull.v1.XmlPullParser
+import java.util.Locale
 
-/** UI-facing language choice. AUTO follows the system languages. */
-enum class LanguagePref { AUTO, GERMAN, ENGLISH }
+private const val ANDROID_NS = "http://schemas.android.com/apk/res/android"
 
 /**
- * Per-app language via AppCompatDelegate. On API 33+ this delegates to the
- * platform per-app-languages API; below that the appcompat backport persists
- * the choice itself (manifest `autoStoreLocales` service), so we don't mirror
- * it in DataStore. Setting a locale recreates the activity, which re-reads the
- * current value for the dropdown.
+ * Per-app language via AppCompatDelegate, driven by res/xml/locales_config.xml.
+ *
+ * That file is the single source of truth for which languages we ship: dropping
+ * in a values-<tag> translation and adding a matching `<locale>` entry makes the
+ * language show up here and in the system per-app-language settings, with no
+ * other code change. The system-default choice is represented as `null`.
+ *
+ * On API 33+ this delegates to the platform per-app-languages API; below that
+ * the appcompat backport persists the choice itself (manifest `autoStoreLocales`
+ * service), so we don't mirror it in DataStore. Setting a locale recreates the
+ * activity, which re-reads the current value for the picker.
  */
 object AppLanguage {
 
-    fun current(): LanguagePref {
-        val locales = AppCompatDelegate.getApplicationLocales()
-        if (locales.isEmpty) return LanguagePref.AUTO
-        return when (locales[0]?.language) {
-            "de" -> LanguagePref.GERMAN
-            "en" -> LanguagePref.ENGLISH
-            else -> LanguagePref.AUTO
+    /**
+     * The BCP-47 tags the app ships translations for, in declaration order, as
+     * listed in locales_config.xml. Returns whatever could be parsed; a missing
+     * or malformed config yields an empty list (the picker then offers only the
+     * system-default entry rather than crashing).
+     */
+    fun supportedTags(context: Context): List<String> {
+        val tags = mutableListOf<String>()
+        val parser = context.resources.getXml(R.xml.locales_config)
+        try {
+            var event = parser.eventType
+            while (event != XmlPullParser.END_DOCUMENT) {
+                if (event == XmlPullParser.START_TAG && parser.name == "locale") {
+                    parser.getAttributeValue(ANDROID_NS, "name")?.let(tags::add)
+                }
+                event = parser.next()
+            }
+        } catch (_: Exception) {
+            // Fall back to whatever was parsed before the failure.
+        } finally {
+            parser.close()
         }
+        return tags
     }
 
-    fun apply(pref: LanguagePref) {
-        val locales = when (pref) {
-            LanguagePref.AUTO -> LocaleListCompat.getEmptyLocaleList()
-            LanguagePref.GERMAN -> LocaleListCompat.forLanguageTags("de")
-            LanguagePref.ENGLISH -> LocaleListCompat.forLanguageTags("en")
+    /** The applied app language as a BCP-47 tag, or `null` when following the system. */
+    fun currentTag(): String? {
+        val locales = AppCompatDelegate.getApplicationLocales()
+        return if (locales.isEmpty) null else locales[0]?.toLanguageTag()
+    }
+
+    /** Apply a BCP-47 tag, or `null` to follow the system languages. */
+    fun apply(tag: String?) {
+        val locales = if (tag == null) {
+            LocaleListCompat.getEmptyLocaleList()
+        } else {
+            LocaleListCompat.forLanguageTags(tag)
         }
         AppCompatDelegate.setApplicationLocales(locales)
     }
+
+    /**
+     * The autonym for a tag — the language's own name in its own script, e.g.
+     * "Deutsch", "English", "Français" — so users find their language regardless
+     * of the current UI language. Capitalised per the language's own rules.
+     */
+    fun displayName(tag: String): String {
+        val locale = Locale.forLanguageTag(tag)
+        return locale.getDisplayName(locale)
+            .replaceFirstChar { if (it.isLowerCase()) it.titlecase(locale) else it.toString() }
+    }
 }

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

@@ -204,11 +204,15 @@ private fun SettingsHub(
 
 @Composable
 private fun LanguageRow(position: Position) {
+    val context = LocalContext.current
     // Setting a locale recreates the activity; mirror the choice locally so the
     // row updates instantly even before the recreation lands.
-    var current by remember { mutableStateOf(AppLanguage.current()) }
+    var current by remember { mutableStateOf(AppLanguage.currentTag()) }
     var showDialog by remember { mutableStateOf(false) }
 
+    // null = follow the system; the rest are BCP-47 tags from locales_config.xml.
+    val options = remember { listOf<String?>(null) + AppLanguage.supportedTags(context) }
+
     GroupedRow(
         title = stringResource(R.string.settings_language),
         summary = languageLabel(current),
@@ -220,7 +224,7 @@ private fun LanguageRow(position: Position) {
     if (showDialog) {
         OptionPicker(
             title = stringResource(R.string.settings_language),
-            options = LanguagePref.entries,
+            options = options,
             selected = current,
             label = { languageLabel(it) },
             onSelect = {
@@ -848,10 +852,5 @@ private fun weekStartLabel(pref: WeekStartPref): String = stringResource(
 )
 
 @Composable
-private fun languageLabel(pref: LanguagePref): String = stringResource(
-    when (pref) {
-        LanguagePref.AUTO -> R.string.settings_language_auto
-        LanguagePref.GERMAN -> R.string.settings_language_german
-        LanguagePref.ENGLISH -> R.string.settings_language_english
-    },
-)
+private fun languageLabel(tag: String?): String =
+    if (tag == null) stringResource(R.string.settings_language_auto) else AppLanguage.displayName(tag)

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

@@ -268,8 +268,6 @@
     <string name="settings_section_language">Sprache</string>
     <string name="settings_language">App-Sprache</string>
     <string name="settings_language_auto">Systemstandard</string>
-    <string name="settings_language_german">Deutsch</string>
-    <string name="settings_language_english">English</string>
     <!-- Hub category subtitles -->
     <string name="settings_appearance_subtitle">Design, dynamische Farben, Wochenstart</string>
     <string name="settings_event_form_subtitle">Standardfelder für neue Termine</string>

app/src/main/res/values-night/colors.xml

@@ -0,0 +1,6 @@
+<resources>
+    <!-- Dark-scheme window backdrop, matching the Compose dark background/surface
+         (#101316) so activity recreation (e.g. language switch) doesn't flash a
+         lighter grey. See values/colors.xml. -->
+    <color name="window_background">#FF101316</color>
+</resources>

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

@@ -3,4 +3,8 @@
     <color name="seed">#FF5C6B7A</color>
     <!-- Adaptive icon background -->
     <color name="ic_launcher_background">#FF5C6B7A</color>
+    <!-- Window backdrop shown during activity recreation (e.g. on a language
+         switch). Matches the Compose light scheme background/surface so the
+         recreation is seamless; overridden for dark in values-night. -->
+    <color name="window_background">#FFFBFCFE</color>
 </resources>

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

@@ -265,8 +265,6 @@
     <string name="settings_section_language">Language</string>
     <string name="settings_language">App language</string>
     <string name="settings_language_auto">System default</string>
-    <string name="settings_language_german">Deutsch</string>
-    <string name="settings_language_english">English</string>
     <!-- Hub category subtitles -->
     <string name="settings_appearance_subtitle">Theme, dynamic colour, week start</string>
     <string name="settings_event_form_subtitle">Default fields for new events</string>

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

@@ -1,5 +1,10 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
-    <style name="Theme.Calendula" parent="android:Theme.Material.Light.NoActionBar">
+    <!-- AppCompat (DayNight) parent so MainActivity can be an AppCompatActivity,
+         which is required for AppCompatDelegate.setApplicationLocales (the in-app
+         language picker) to sync to the system. Actual colours are driven by the
+         Compose theme; this is essentially the launch/backdrop theme. -->
+    <style name="Theme.Calendula" parent="Theme.AppCompat.DayNight.NoActionBar">
+        <item name="android:windowBackground">@color/window_background</item>
         <item name="android:statusBarColor">@android:color/transparent</item>
         <item name="android:navigationBarColor">@android:color/transparent</item>
         <item name="android:windowLightStatusBar">true</item>

app/src/main/res/xml/locales_config.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+    The languages Calendula ships translations for. This is the single source of
+    truth: each entry must have a matching res/values-<tag>/strings.xml, and is
+    surfaced automatically in both the in-app language picker (parsed at runtime
+    by AppLanguage) and the system per-app language settings (Android 13+, via
+    android:localeConfig in the manifest). To add a community translation, drop
+    in the values-<tag> folder and add one <locale> line here.
+-->
+<locale-config xmlns:android="http://schemas.android.com/apk/res/android">
+    <locale android:name="en" />
+    <locale android:name="de" />
+</locale-config>

scripts/check_translations.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+"""Validate Android translation resources against the base strings.xml.
+
+Community translations live in ``app/src/main/res/values-<locale>/strings.xml``
+and are produced via Weblate. This guard keeps incoming translation PRs honest:
+
+  * every translation file must be well-formed XML;
+  * a translation must not define keys absent from the base — those are stale
+    keys left behind after a rename/removal upstream;
+  * a translation must not translate strings marked ``translatable="false"`` in
+    the base (URLs, IDs and the like).
+
+Missing keys are *allowed* and only reported as coverage: a missing string
+falls back to the English base at runtime, so partial translations are fine
+(this mirrors the lint config, which downgrades ``MissingTranslation``).
+
+Exits non-zero if any error is found. Errors are emitted as Gitea/GitHub
+Actions ``::error`` annotations so they surface inline on the PR.
+"""
+from __future__ import annotations
+
+import sys
+import xml.etree.ElementTree as ET
+from pathlib import Path
+
+RES_DIR = Path("app/src/main/res")
+BASE = RES_DIR / "values" / "strings.xml"
+RESOURCE_TAGS = ("string", "plurals", "string-array")
+
+
+def entries(path: Path) -> dict[str, bool]:
+    """Map resource name -> is-translatable for every entry in ``path``."""
+    root = ET.parse(path).getroot()
+    return {
+        el.attrib["name"]: el.attrib.get("translatable", "true") != "false"
+        for el in root
+        if el.tag in RESOURCE_TAGS and "name" in el.attrib
+    }
+
+
+def main() -> int:
+    if not BASE.exists():
+        print(f"::error::base resource file {BASE} not found", file=sys.stderr)
+        return 1
+
+    base = entries(BASE)
+    base_keys = set(base)
+    nontranslatable = {name for name, ok in base.items() if not ok}
+    translatable_total = len(base_keys - nontranslatable)
+
+    files = sorted(RES_DIR.glob("values-*/strings.xml"))
+    if not files:
+        print("No translation files found (values-*/strings.xml).")
+        return 0
+
+    errors = 0
+    for path in files:
+        locale = path.parent.name[len("values-"):]
+        try:
+            translated = entries(path)
+        except ET.ParseError as exc:
+            print(f"::error file={path}::{locale}: malformed XML: {exc}")
+            errors += 1
+            continue
+
+        keys = set(translated)
+        stale = sorted(keys - base_keys)
+        translated_fixed = sorted(keys & nontranslatable)
+        missing = base_keys - nontranslatable - keys
+
+        for name in stale:
+            print(f"::error file={path}::{locale}: stale key '{name}' is not in the base strings.xml")
+            errors += 1
+        for name in translated_fixed:
+            print(
+                f"::error file={path}::{locale}: key '{name}' is translatable=\"false\" "
+                "in the base and must not be translated"
+            )
+            errors += 1
+
+        covered = translatable_total - len(missing)
+        pct = covered * 100 // translatable_total if translatable_total else 100
+        verdict = "OK" if not (stale or translated_fixed) else "FAIL"
+        print(f"{locale:<10} {covered}/{translatable_total} keys ({pct}%) — {verdict}")
+
+    if errors:
+        print(f"\n{errors} translation error(s) found.", file=sys.stderr)
+        return 1
+    print("\nAll translation files are consistent with the base.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())