refactor: set traversal order for player

feature/records/src/commonMain/kotlin/bzh/ajaury/chombev/player/ui/PlayerControl.kt

@@ -58,6 +58,7 @@ fun PlayerControl(
                 contentAlignment = Alignment.Center,
             ) {
                 SpeedPreferenceButton(
+                    modifier = Modifier.traversalOrder(PlayerTraversalOrder.PLAYBACK_SETTINGS),
                     isActive = isPlaybackModified,
                     onSpeedClicked = onSpeedClicked,
                 )
@@ -69,17 +70,20 @@ fun PlayerControl(
                 verticalAlignment = Alignment.CenterVertically,
             ) {
                 PreviousButton(
+                    modifier = Modifier.traversalOrder(PlayerTraversalOrder.PREVIOUS),
                     canGoToPreviousSentence = canGoToPreviousSentence,
                     onPreviousSentenceClicked = onPreviousSentenceClicked,
                 )
 
                 PlayButton(
+                    modifier = Modifier.traversalOrder(PlayerTraversalOrder.PLAY),
                     playbackState = playbackState,
                     breakDuration = breakBetweenPhrases,
                     onMainPlayActionButtonClicked = onMainPlayActionButtonClicked,
                 )
 
                 NextButton(
+                    modifier = Modifier.traversalOrder(PlayerTraversalOrder.NEXT),
                     canGoToNextSentence = canGoToNextSentence,
                     onNextSentenceClicked = onNextSentenceClicked,
                 )

feature/records/src/commonMain/kotlin/bzh/ajaury/chombev/player/ui/PlayerScreen.kt

@@ -32,6 +32,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.shadow
 import androidx.compose.ui.semantics.clearAndSetSemantics
 import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.isTraversalGroup
 import androidx.compose.ui.semantics.onClick
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.style.TextOverflow
@@ -116,6 +117,9 @@ fun PlayerScreen(
     var showSpeed by remember { mutableStateOf(false) }
 
     Scaffold(
+        // Root of the screen reader order defined by PlayerTraversalOrder, which interleaves the
+        // top bar and the controls.
+        modifier = Modifier.semantics { isTraversalGroup = true },
         topBar = {
             PlayerTopBar(
                 uiState = uiState,
@@ -191,7 +195,11 @@ private fun PlayerTopBar(
     showPreferences: () -> Unit,
 ) {
     TopAppBar(
-        modifier = Modifier.shadow(elevation = 2.dp),
+        modifier = Modifier
+            .shadow(elevation = 2.dp)
+            // TopAppBar makes itself a traversal group, which would keep its subtitle settings
+            // button next to the title. Flattened so PlayerTraversalOrder can move it last.
+            .semantics { isTraversalGroup = false },
         title = {
             // Animate the title in as it loads, and between records: the record data isn't there on
             // the first frame, so fade + rise it into place once uiState carries it.
@@ -204,7 +212,9 @@ private fun PlayerTopBar(
                 label = "PlayerTitle",
             ) { (emoji, title) ->
                 Row(
-                    modifier = Modifier.clearAndSetSemantics {
+                    modifier = Modifier
+                        .traversalOrder(PlayerTraversalOrder.TITLE)
+                        .clearAndSetSemantics {
                             contentDescription = title.translation ?: title.transcription
                         },
                     verticalAlignment = Alignment.CenterVertically,
@@ -242,7 +252,9 @@ private fun PlayerTopBar(
             val openSettingsLabel = stringResource(Res.string.settings_open_action_description)
             IconButton(
                 // Names the action: "double-tap to open settings" rather than the generic "to activate".
-                modifier = Modifier.semantics {
+                modifier = Modifier
+                    .traversalOrder(PlayerTraversalOrder.SUBTITLE_SETTINGS)
+                    .semantics {
                         onClick(label = openSettingsLabel) {
                             showPreferences()
                             true
@@ -265,6 +277,7 @@ private fun BackButton(onBackClicked: () -> Unit) {
     IconButton(
         onClick = onBackClicked,
         modifier = Modifier
+            .traversalOrder(PlayerTraversalOrder.BACK)
             .semantics {
                 onClick(label = backActionLabel) {
                     onBackClicked()

feature/records/src/commonMain/kotlin/bzh/ajaury/chombev/player/ui/PlayerTraversalOrder.kt

@@ -0,0 +1,30 @@
+package bzh.ajaury.chombev.player.ui
+
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.isTraversalGroup
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.semantics.traversalIndex
+
+/**
+ * Screen reader order on the player, which departs from the visual layout: the title and back
+ * button first, then the transport controls, the settings last.
+ */
+internal enum class PlayerTraversalOrder {
+    TITLE,
+    BACK,
+    PLAY,
+    PREVIOUS,
+    NEXT,
+    PLAYBACK_SETTINGS,
+    SUBTITLE_SETTINGS,
+}
+
+/**
+ * Places this element at [order] in the player's screen reader order. Grouped so that an element
+ * made of several nodes (e.g. the play button and its break ring) moves as a whole.
+ */
+internal fun Modifier.traversalOrder(order: PlayerTraversalOrder): Modifier =
+    semantics {
+        isTraversalGroup = true
+        traversalIndex = order.ordinal.toFloat()
+    }