feat: on-the-fly SMS translation via offline-translator AIDL

Adds a small `:translate` Gradle module that translates received SMS /
MMS bubbles and conversation-list snippets on the fly by binding to the
offline-translator app on F-Droid (`dev.davidv.translator`). The actual
translation runs there — Mozilla Bergamot/Marian on-device — so this
patch ships no model, no inference, and no permissions beyond an
Android 11+ <queries> block for package visibility.

Behavior:
- User-defined source-language allowlist + target language in
  Settings → Translation (right after Language). Off by default.
- Auto-translate fires on RecyclerView bind for received bubbles and
  conversation snippets. Detection uses ML Kit Language Identification
  (CLD3, on-device). Once dev.davidv.translator exposes a
  detectLanguage() AIDL method we'll route through that and drop ML Kit.
- AIDL latency is sub-second, so the bubble just quietly swaps from
  the original to the translation — no loading spinner.
- Tap the translate icon next to a bubble to flip it back to the
  original; tap again to flip to the translation. Cached in process
  memory.
- Long-press → ⋮ → Translate forces a one-off translation regardless
  of the allowlist (useful for messages in non-allowlisted languages),
  with a toast surfacing AIDL errors like 'language pack not installed'.
- Copy / Share / Select on a translated bubble captures what the user
  sees, not the underlying source body.
- Silently no-ops when offline-translator isn't installed; settings
  screen shows an F-Droid install banner.
- Translation Settings is a regular Fossify sub-screen with
  MyAppBarLayout + MaterialToolbar + NestedScrollView, matching
  Manage Blocked Numbers / Keywords / SettingsActivity.

No new database, no service, no boot receiver, no foreground service.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/org/fossify/messages/activities/SettingsActivity.kt

@@ -106,6 +106,7 @@ class SettingsActivity : SimpleActivity() {
         setupLanguage()
         setupManageBlockedNumbers()
         setupManageBlockedKeywords()
+        setupTranslation()
         setupChangeDateTimeFormat()
         setupFontSize()
         setupShowCharacterCounter()
@@ -230,6 +231,12 @@ class SettingsActivity : SimpleActivity() {
         }
     }
 
+    private fun setupTranslation() = binding.apply {
+        settingsTranslationHolder.setOnClickListener {
+            startActivity(Intent(this@SettingsActivity, org.fossify.messages.translate.TranslationSettingsActivity::class.java))
+        }
+    }
+
     private fun setupChangeDateTimeFormat() = binding.apply {
         settingsChangeDateTimeFormatHolder.setOnClickListener {
             ChangeDateTimeFormatDialog(this@SettingsActivity) {

app/src/main/kotlin/org/fossify/messages/adapters/BaseConversationsAdapter.kt

@@ -19,6 +19,9 @@ import org.fossify.commons.extensions.getContrastColor
 import org.fossify.commons.extensions.getTextSize
 import org.fossify.commons.extensions.setupViewBackground
 import org.fossify.commons.helpers.FontHelper
+import org.fossify.messages.R
+import org.fossify.messages.translate.TranslateConfig
+import org.fossify.messages.translate.Translator
 import org.fossify.commons.helpers.SimpleContactsHelper
 import org.fossify.commons.helpers.ensureBackgroundThread
 import org.fossify.commons.views.MyRecyclerView
@@ -44,6 +47,7 @@ abstract class BaseConversationsAdapter(
     RecyclerViewFastScroller.OnPopupTextUpdate {
     private var fontSize = activity.getTextSize()
     private var drafts = HashMap<Long, String>()
+    private val translateConfig by lazy { TranslateConfig(activity) }
 
     private var recyclerViewState: Parcelable? = null
 
@@ -160,8 +164,20 @@ abstract class BaseConversationsAdapter(
             }
 
             conversationBodyShort.apply {
-                text = smsDraft ?: conversation.snippet
+                val original = smsDraft ?: conversation.snippet
+                text = original
                 setTextSize(TypedValue.COMPLEX_UNIT_PX, fontSize * 0.9f)
+                if (smsDraft == null && original.isNotEmpty()) {
+                    val view = this
+                    val token = conversation.threadId
+                    setTag(R.id.conversation_body_short, token)
+                    Translator.maybeAutoTranslate(original, activity, translateConfig) { result ->
+                        if (view.getTag(R.id.conversation_body_short) == token &&
+                            result is Translator.Result.Success) {
+                            view.text = result.translated
+                        }
+                    }
+                }
             }
 
             conversationDate.apply {

app/src/main/kotlin/org/fossify/messages/adapters/ThreadAdapter.kt

@@ -41,6 +41,7 @@ import org.fossify.commons.extensions.getTextSize
 import org.fossify.commons.extensions.getTimeFormat
 import org.fossify.commons.extensions.shareTextIntent
 import org.fossify.commons.extensions.showErrorToast
+import org.fossify.commons.extensions.toast
 import org.fossify.commons.extensions.usableScreenSize
 import org.fossify.commons.helpers.FontHelper
 import org.fossify.commons.helpers.SimpleContactsHelper
@@ -87,6 +88,7 @@ import org.fossify.messages.models.ThreadItem.ThreadDateTime
 import org.fossify.messages.models.ThreadItem.ThreadError
 import org.fossify.messages.models.ThreadItem.ThreadSending
 import org.fossify.messages.models.ThreadItem.ThreadSent
+import org.fossify.messages.translate.TranslationBubbleBinder
 import org.joda.time.DateTime
 
 class ThreadAdapter(
@@ -101,6 +103,7 @@ class ThreadAdapter(
     @SuppressLint("MissingPermission")
     private val hasMultipleSIMCards = (activity.subscriptionManagerCompat().activeSubscriptionInfoList?.size ?: 0) > 1
     private val maxChatBubbleWidth = (activity.usableScreenSize.x * 0.8f).toInt()
+    private val translationBinder = TranslationBubbleBinder(activity)
 
     companion object {
         private const val MAX_MEDIA_HEIGHT_RATIO = 3
@@ -130,6 +133,8 @@ class ThreadAdapter(
             findItem(R.id.cab_share).isVisible = isOneItemSelected && hasText
             findItem(R.id.cab_forward_message).isVisible = isOneItemSelected
             findItem(R.id.cab_select_text).isVisible = isOneItemSelected && hasText
+            findItem(R.id.cab_translate).isVisible =
+                isOneItemSelected && hasText && selectedMessages.firstOrNull()?.isReceivedMessage() == true
             findItem(R.id.cab_properties).isVisible = isOneItemSelected
             findItem(R.id.cab_restore).isVisible = isRecycleBin
         }
@@ -146,6 +151,7 @@ class ThreadAdapter(
             R.id.cab_share -> shareText()
             R.id.cab_forward_message -> forwardMessage()
             R.id.cab_select_text -> selectText()
+            R.id.cab_translate -> translateSelectedMessage()
             R.id.cab_delete -> askConfirmDelete()
             R.id.cab_restore -> askConfirmRestore()
             R.id.cab_select_all -> selectAll()
@@ -226,13 +232,15 @@ class ThreadAdapter(
         if (selectedMessages.isEmpty()) return
 
         val textToCopy = if (selectedMessages.size == 1) {
-            selectedMessages.first().body
+            val msg = selectedMessages.first()
+            translationBinder.visibleText(msg.id, msg.body).toString()
         } else {
             selectedMessages.filter { it.body.isNotEmpty() }.joinToString("\n\n") { message ->
                 val format = "${activity.config.dateFormat}, ${activity.getTimeFormat()}"
                 val dateTime = DateTime(message.millis()).toString(format)
                 val sender = if (message.isReceivedMessage()) message.senderName else activity.getString(R.string.me)
-                "[$dateTime] $sender: ${message.body}"
+                val visible = translationBinder.visibleText(message.id, message.body)
+                "[$dateTime] $sender: $visible"
             }
         }
 
@@ -255,13 +263,34 @@ class ThreadAdapter(
 
     private fun shareText() {
         val firstItem = getSelectedItems().firstOrNull() as? Message ?: return
-        activity.shareTextIntent(firstItem.body)
+        activity.shareTextIntent(translationBinder.visibleText(firstItem.id, firstItem.body).toString())
     }
 
     private fun selectText() {
         val firstItem = getSelectedItems().firstOrNull() as? Message ?: return
-        if (firstItem.body.trim().isNotEmpty()) {
-            SelectTextDialog(activity, firstItem.body)
+        val visible = translationBinder.visibleText(firstItem.id, firstItem.body).toString()
+        if (visible.trim().isNotEmpty()) {
+            SelectTextDialog(activity, visible)
+        }
+    }
+
+    private fun translateSelectedMessage() {
+        val message = getSelectedItems().firstOrNull() as? Message ?: return
+        if (message.body.isBlank()) return
+        val position = currentList.indexOf(message)
+        translationBinder.preloadTranslation(message.id, message.body) { result ->
+            when (result) {
+                is org.fossify.messages.translate.Translator.Result.Success -> {
+                    if (position >= 0) notifyItemChanged(position)
+                }
+                is org.fossify.messages.translate.Translator.Result.Failed -> {
+                    activity.toast(activity.getString(org.fossify.messages.translate.R.string.translation_failed) + ": " + result.reason)
+                }
+                org.fossify.messages.translate.Translator.Result.Skipped -> {
+                    activity.toast(org.fossify.messages.translate.R.string.translation_failed)
+                }
+            }
+            finishActMode()
         }
     }
 
@@ -431,6 +460,20 @@ class ThreadAdapter(
                 setLinkTextColor(activity.getProperPrimaryColor())
             }
 
+            // Translation: auto-translate if the rule allowlist matches; the
+            // binder also manages the show-original toggle on the icon.
+            if (message.body.isNotEmpty()) {
+                threadMessageTranslateIcon.setColorFilter(textColor)
+                translationBinder.bind(
+                    messageId = message.id,
+                    body = message.body,
+                    bodyView = threadMessageBody,
+                    iconView = threadMessageTranslateIcon,
+                )
+            } else {
+                threadMessageTranslateIcon.visibility = View.GONE
+            }
+
             if (!activity.isFinishing && !activity.isDestroyed) {
                 val contactLetterIcon = SimpleContactsHelper(activity).getContactLetterIcon(message.senderName)
                 val placeholder = contactLetterIcon.toDrawable(activity.resources)

app/src/main/res/layout/activity_settings.xml

@@ -113,6 +113,21 @@
 
             </RelativeLayout>
 
+            <RelativeLayout
+                android:id="@+id/settings_translation_holder"
+                style="@style/SettingsHolderTextViewOneLinerStyle"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content">
+
+                <org.fossify.commons.views.MyTextView
+                    android:id="@+id/settings_translation"
+                    style="@style/SettingsTextLabelStyle"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="@string/translation_settings" />
+
+            </RelativeLayout>
+
             <RelativeLayout
                 android:id="@+id/settings_change_date_time_format_holder"
                 style="@style/SettingsHolderTextViewOneLinerStyle"

app/src/main/res/layout/item_message.xml

@@ -65,5 +65,18 @@
             android:textSize="@dimen/normal_text_size"
             tools:drawableEndCompat="@drawable/scheduled_message_icon"
             tools:text="Message content" />
+
+        <ImageView
+            android:id="@+id/thread_message_translate_icon"
+            android:layout_width="20dp"
+            android:layout_height="20dp"
+            android:layout_below="@+id/thread_message_body"
+            android:layout_alignStart="@+id/thread_message_body"
+            android:layout_marginStart="@dimen/normal_margin"
+            android:layout_marginTop="-2dp"
+            android:padding="2dp"
+            android:src="@drawable/ic_translate_vector"
+            android:visibility="gone"
+            tools:ignore="ContentDescription" />
     </RelativeLayout>
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/menu/cab_thread.xml

@@ -37,6 +37,11 @@
         android:showAsAction="never"
         android:title="@string/select_text"
         app:showAsAction="never" />
+    <item
+        android:id="@+id/cab_translate"
+        android:showAsAction="never"
+        android:title="@string/translate"
+        app:showAsAction="never" />
     <item
         android:id="@+id/cab_select_all"
         android:icon="@drawable/ic_select_all_vector"