refactor: improve accessibility for subtitle size settings

data/resources/src/commonMain/composeResources/values/strings.xml

@@ -17,6 +17,7 @@
     <string name="subtitle_translation_label">Traduction (FR)</string>
     <string name="subtitle_translation_description">Afficher la traduction française</string>
     <string name="subtitle_text_size_label">Taille du texte</string>
+    <string name="subtitle_text_size_value">%1$d %</string>
     <string name="subtitle_text_size_decrease">Réduire la taille du texte</string>
     <string name="subtitle_text_size_increase">Augmenter la taille du texte</string>
     <string name="subtitle_marked_letters_label">Marques de prononciation</string>

feature/records/src/commonMain/kotlin/bzh/ajaury/chombev/preferences/ui/SubtitlePreferencesBottomSheet.kt

@@ -20,6 +20,14 @@ import androidx.compose.material3.rememberBottomSheetState
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.CustomAccessibilityAction
+import androidx.compose.ui.semantics.ProgressBarRangeInfo
+import androidx.compose.ui.semantics.clearAndSetSemantics
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.customActions
+import androidx.compose.ui.semantics.progressBarRangeInfo
+import androidx.compose.ui.semantics.setProgress
+import androidx.compose.ui.semantics.stateDescription
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import bzh.ajaury.chombev.preferences.model.SubtitlePreferences
@@ -30,6 +38,7 @@ import bzh.ajaury.chombev.resources.generated.resources.subtitle_preferences_tit
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_text_size_decrease
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_text_size_increase
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_text_size_label
+import bzh.ajaury.chombev.resources.generated.resources.subtitle_text_size_value
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_transcription_description
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_transcription_label
 import bzh.ajaury.chombev.resources.generated.resources.subtitle_translation_description
@@ -120,10 +129,50 @@ private fun SubtitleTextSizeControl(
     onDecrease: () -> Unit = {},
     onIncrease: () -> Unit = {},
 ) {
+    val label = stringResource(Res.string.subtitle_text_size_label)
+    val value = stringResource(Res.string.subtitle_text_size_value, (textScale * 100).roundToInt())
+    val decreaseLabel = stringResource(Res.string.subtitle_text_size_decrease)
+    val increaseLabel = stringResource(Res.string.subtitle_text_size_increase)
+    // The steps are uneven (0.1 then 0.2 apart), so screen readers adjust a step index instead.
+    val steps = SubtitlePreferences.TEXT_SCALE_STEPS
+    val stepIndex = steps.indexOfFirst { it >= textScale - 0.001f }.coerceAtLeast(0)
+
     Row(
         modifier = Modifier
             .fillMaxWidth()
-            .padding(vertical = 8.dp),
+            .padding(vertical = 8.dp)
+            // A single adjustable element for screen readers, like a slider: swiping up or down
+            // changes the size and announces the new value. The buttons only serve touch use.
+            .clearAndSetSemantics {
+                contentDescription = label
+                stateDescription = value
+                progressBarRangeInfo = ProgressBarRangeInfo(
+                    current = stepIndex.toFloat(),
+                    range = 0f..steps.lastIndex.toFloat(),
+                    steps = steps.size - 2,
+                )
+                setProgress { target ->
+                    val targetIndex = target.roundToInt()
+                    when {
+                        targetIndex > stepIndex -> onIncrease()
+                        targetIndex < stepIndex -> onDecrease()
+                        else -> return@setProgress false
+                    }
+                    true
+                }
+                // Same adjustments from the screen reader's actions menu, for users unaware of the
+                // adjust gesture.
+                customActions = listOf(
+                    CustomAccessibilityAction(label = increaseLabel) {
+                        onIncrease()
+                        true
+                    },
+                    CustomAccessibilityAction(label = decreaseLabel) {
+                        onDecrease()
+                        true
+                    },
+                )
+            },
         horizontalArrangement = Arrangement.spacedBy(8.dp),
         verticalAlignment = Alignment.CenterVertically,
     ) {