add a low-data-mode option to disable images

app/src/main/kotlin/com/github/gotify/MarkwonFactory.kt

@@ -40,11 +40,17 @@ import org.commonmark.parser.Parser
 import org.tinylog.kotlin.Logger
 
 internal object MarkwonFactory {
-    fun createForMessage(context: Context, imageLoader: ImageLoader): Markwon {
-        return Markwon.builder(context)
+    fun createForMessage(
+        context: Context,
+        imageLoader: ImageLoader,
+        lowDataMode: Boolean = false
+    ): Markwon {
+        val builder = Markwon.builder(context)
             .usePlugin(CorePlugin.create())
             .usePlugin(MovementMethodPlugin.create(TableAwareMovementMethod.create()))
-            .usePlugin(
+
+        if (!lowDataMode) {
+            builder.usePlugin(
                 CoilImagesPlugin.create(
                     object : CoilImagesPlugin.CoilStore {
                         override fun load(drawable: AsyncDrawable): ImageRequest {
@@ -68,6 +74,9 @@ internal object MarkwonFactory {
                     imageLoader
                 )
             )
+        }
+
+        return builder
             .usePlugin(StrikethroughPlugin.create())
             .usePlugin(TablePlugin.create(context))
             .usePlugin(object : AbstractMarkwonPlugin() {

app/src/main/kotlin/com/github/gotify/messages/ListMessageAdapter.kt

@@ -40,7 +40,8 @@ internal class ListMessageAdapter(
     private val delete: Delete
 ) : ListAdapter<MessageWithImage, ListMessageAdapter.ViewHolder>(DiffCallback) {
     private val prefs: SharedPreferences = PreferenceManager.getDefaultSharedPreferences(context)
-    private val markwon: Markwon = MarkwonFactory.createForMessage(context, imageLoader)
+    private val lowDataMode = prefs.getBoolean(context.getString(R.string.setting_key_low_data_mode), false)
+    private val markwon: Markwon = MarkwonFactory.createForMessage(context, imageLoader, lowDataMode)
 
     private val timeFormatRelative =
         context.resources.getString(R.string.time_format_value_relative)
@@ -81,11 +82,18 @@ internal class ListMessageAdapter(
             holder.message.text = message.message.message
         }
         holder.title.text = message.message.title
-        if (message.image != null) {
-            val url = Utils.resolveAbsoluteUrl("${settings.url}/", message.image)
-            holder.image.load(url, imageLoader) {
-                error(R.drawable.ic_alarm)
-                placeholder(R.drawable.ic_placeholder)
+        if (lowDataMode) {
+            holder.image.visibility = View.GONE
+        } else {
+            holder.image.visibility = View.VISIBLE
+            if (message.image != null) {
+                val url = Utils.resolveAbsoluteUrl("${settings.url}/", message.image)
+                holder.image.load(url, imageLoader) {
+                    error(R.drawable.ic_alarm)
+                    placeholder(R.drawable.ic_placeholder)
+                }
+            } else {
+                holder.image.setImageDrawable(null)
             }
         }
 

app/src/main/kotlin/com/github/gotify/messages/MessagesActivity.kt

@@ -198,23 +198,31 @@ internal class MessagesActivity :
         val menu: Menu = binding.navView.menu
         menu.removeGroup(R.id.apps)
         viewModel.targetReferences.clear()
+
+        val prefs = PreferenceManager.getDefaultSharedPreferences(this)
+        val lowDataMode = prefs.getBoolean(getString(R.string.setting_key_low_data_mode), false)
+
         updateMessagesAndStopLoading(viewModel.messages[viewModel.appId])
         var selectedItem = menu.findItem(R.id.nav_all_messages)
         applications.indices.forEach { index ->
             val app = applications[index]
             val item = menu.add(R.id.apps, index, APPLICATION_ORDER, app.name)
             item.isCheckable = true
             if (app.id == viewModel.appId) selectedItem = item
-            val t = Utils.toDrawable { icon -> item.icon = icon }
-            viewModel.targetReferences.add(t)
-            val request = ImageRequest.Builder(this)
-                .data(Utils.resolveAbsoluteUrl(viewModel.settings.url + "/", app.image))
-                .error(R.drawable.ic_alarm)
-                .placeholder(R.drawable.ic_placeholder)
-                .size(100, 100)
-                .target(t)
-                .build()
-            CoilInstance.get(this).enqueue(request)
+            if (lowDataMode) {
+                item.setIcon(R.drawable.ic_placeholder)
+            } else {
+                val t = Utils.toDrawable { icon -> item.icon = icon }
+                viewModel.targetReferences.add(t)
+                val request = ImageRequest.Builder(this)
+                    .data(Utils.resolveAbsoluteUrl(viewModel.settings.url + "/", app.image))
+                    .error(R.drawable.ic_alarm)
+                    .placeholder(R.drawable.ic_placeholder)
+                    .size(100, 100)
+                    .target(t)
+                    .build()
+                CoilInstance.get(this).enqueue(request)
+            }
         }
         selectAppInMenu(selectedItem)
     }

app/src/main/kotlin/com/github/gotify/settings/SettingsActivity.kt

@@ -78,6 +78,13 @@ internal class SettingsActivity :
 
         override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
             super.onViewCreated(view, savedInstanceState)
+            findPreference<SwitchPreferenceCompat>(
+                getString(R.string.setting_key_low_data_mode)
+            )?.onPreferenceChangeListener =
+                Preference.OnPreferenceChangeListener { _, _ ->
+                    showRestartDialog()
+                    true
+                }
             findPreference<ListPreference>(
                 getString(R.string.setting_key_message_layout)
             )?.onPreferenceChangeListener =

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

@@ -99,6 +99,12 @@
     <string name="setting_prompt_onreceive_intent">Confirm onReceive intents</string>
     <string name="setting_key_prompt_onreceive_intent">prompt_onreceive_intent</string>
     <string name="setting_summary_prompt_onreceive_intent">If enabled, a dialog is shown before onReceive.intentUrl is executed.</string>
+
+    <string name="setting_general">General</string>
+    <string name="setting_low_data_mode">Low data mode</string>
+    <string name="setting_low_data_mode_summary">Disable loading images from the server</string>
+    <string name="setting_key_low_data_mode">low_data_mode</string>
+
     <string name="push_message">Push message</string>
     <string name="appListDescription">App:</string>
     <string name="priorityDescription">Priority:</string>

app/src/main/res/xml/root_preferences.xml

@@ -2,6 +2,14 @@
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <PreferenceCategory app:title="@string/setting_general">
+        <SwitchPreferenceCompat
+            android:defaultValue="false"
+            android:key="@string/setting_key_low_data_mode"
+            android:title="@string/setting_low_data_mode"
+            android:summary="@string/setting_low_data_mode_summary" />
+    </PreferenceCategory>
+
     <PreferenceCategory app:title="@string/settings_appearance" >
         <ListPreference
             android:defaultValue="@string/theme_default"