new: add adjustable subtitle text size in player and preferences UI

data/preferences/src/commonMain/kotlin/fr/ajaury/gwenedeg/preferences/data/InMemoryPreferencesRepository.kt

@@ -27,6 +27,10 @@ internal class InMemoryPreferencesRepository : PreferencesRepository {
         subtitleState.update { it.copy(showTranslation = enabled) }
     }
 
+    override suspend fun setSubtitleTextScale(scale: Float) {
+        subtitleState.update { it.copy(textScale = scale) }
+    }
+
     override suspend fun setPlaybackSpeed(speed: Float) {
         playbackState.update { it.copy(speed = speed) }
     }

data/preferences/src/commonMain/kotlin/fr/ajaury/gwenedeg/preferences/domain/PreferencesRepository.kt

@@ -13,5 +13,7 @@ interface PreferencesRepository {
 
     suspend fun setShowTranslation(enabled: Boolean)
 
+    suspend fun setSubtitleTextScale(scale: Float)
+
     suspend fun setPlaybackSpeed(speed: Float)
 }

data/preferences/src/commonMain/kotlin/fr/ajaury/gwenedeg/preferences/model/SubtitlePreferences.kt

@@ -1,12 +1,30 @@
 package fr.ajaury.gwenedeg.preferences.model
 
 /**
- * User preferences controlling which subtitle lines are displayed on the player.
+ * User preferences controlling the subtitle display on the player.
  *
  * @property showTranscription whether the Breton (BZH) transcription line is shown.
  * @property showTranslation whether the French (FR) translation line is shown.
+ * @property textScale multiplier applied to the subtitle font size (see [TEXT_SCALE_STEPS]).
  */
 data class SubtitlePreferences(
     val showTranscription: Boolean = true,
     val showTranslation: Boolean = true,
-)
+    val textScale: Float = DEFAULT_TEXT_SCALE,
+) {
+    companion object {
+        const val DEFAULT_TEXT_SCALE = 1f
+
+        /** Allowed text-scale steps: 0.1 increments up to x1, then 0.2 increments up to x2. */
+        val TEXT_SCALE_STEPS: List<Float> =
+            listOf(0.5f, 0.6f, 0.7f, 0.8f, 0.9f, 1.0f, 1.2f, 1.4f, 1.6f, 1.8f, 2.0f)
+
+        /** The next allowed step above [scale], or the maximum when already at the top. */
+        fun nextTextScale(scale: Float): Float =
+            TEXT_SCALE_STEPS.firstOrNull { it > scale } ?: TEXT_SCALE_STEPS.last()
+
+        /** The previous allowed step below [scale], or the minimum when already at the bottom. */
+        fun previousTextScale(scale: Float): Float =
+            TEXT_SCALE_STEPS.lastOrNull { it < scale } ?: TEXT_SCALE_STEPS.first()
+    }
+}

data/preferences/src/dataStoreMain/kotlin/fr/ajaury/gwenedeg/preferences/data/DataStorePreferencesRepository.kt

@@ -32,6 +32,8 @@ internal class DataStorePreferencesRepository(
 
     override suspend fun setShowTranslation(enabled: Boolean) = edit { it[ShowTranslationKey] = enabled }
 
+    override suspend fun setSubtitleTextScale(scale: Float) = edit { it[SubtitleTextScaleKey] = scale }
+
     override suspend fun setPlaybackSpeed(speed: Float) = edit { it[PlaybackSpeedKey] = speed }
 
     private suspend fun edit(transform: (MutablePreferences) -> Unit) {
@@ -43,6 +45,7 @@ internal class DataStorePreferencesRepository(
         return SubtitlePreferences(
             showTranscription = this[ShowTranscriptionKey] ?: defaults.showTranscription,
             showTranslation = this[ShowTranslationKey] ?: defaults.showTranslation,
+            textScale = this[SubtitleTextScaleKey] ?: defaults.textScale,
         )
     }
 
@@ -54,6 +57,7 @@ internal class DataStorePreferencesRepository(
     private companion object {
         val ShowTranscriptionKey = booleanPreferencesKey("show_transcription")
         val ShowTranslationKey = booleanPreferencesKey("show_translation")
+        val SubtitleTextScaleKey = floatPreferencesKey("subtitle_text_scale")
         val PlaybackSpeedKey = floatPreferencesKey("playback_speed")
     }
 }