player: title header + scrollable description in info/comments (#23, #24)

The info and comments side panels showed a generic "Info"/"Comments" label,
which read as an empty black bar with no clue which video it belonged to. Both
now show the video's title instead (#24, and the same complaint in #23).

The info panel's description also could not be scrolled with the D-pad: a plain
Text in a LazyColumn takes no focus, so a long description was unreadable past
the first screenful unless it happened to contain links. It is now a focusable,
D-pad-scrollable box; Down at the bottom hands focus to the link list, Left
closes the panel (#23).

app/src/main/java/net/jeena/jtubetv/ui/player/PlayerSidebar.kt

@@ -4,6 +4,10 @@ import android.view.KeyEvent
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.focusable
+import androidx.compose.foundation.gestures.animateScrollBy
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -93,15 +97,16 @@ fun PlayerSidebar(
             .width(SIDEBAR_WIDTH)
             .background(SidebarBg),
     ) {
+        // Header = the video's title (issue #23/#24): the old generic "Info" /
+        // "Comments" label read as an empty black bar with no context about
+        // which video the panel belongs to. Playlists keeps its own label.
         Text(
-            text = when (mode) {
-                "playlists" -> "Playlists"
-                "info" -> "Info"
-                else -> "Comments"
-            },
+            text = if (mode == "playlists") "Playlists" else detail.name,
             color = Color.White,
             style = MaterialTheme.typography.titleMedium,
-            modifier = Modifier.padding(20.dp),
+            maxLines = 2,
+            overflow = androidx.compose.ui.text.style.TextOverflow.Ellipsis,
+            modifier = Modifier.padding(start = 20.dp, end = 20.dp, top = 16.dp, bottom = 10.dp),
         )
         when (mode) {
             "playlists" -> PlaylistsColumn(detail, onDismiss)
@@ -161,19 +166,7 @@ private fun InfoColumn(
         .distinct()
         .toList()
 
-    val firstLinkFocus = remember { FocusRequester() }
-    LaunchedEffect(links) {
-        if (links.isNotEmpty()) {
-            kotlinx.coroutines.delay(150)
-            runCatching { firstLinkFocus.requestFocus() }
-        }
-    }
-
-    LazyColumn(Modifier.fillMaxSize()) {
-        if (description.isNotBlank()) {
-            item(key = "desc") {
-                Text(
-                    text = buildAnnotatedString {
+    val annotated = buildAnnotatedString {
         var rest = description
         while (true) {
             val match = UrlPattern.find(rest) ?: break
@@ -194,26 +187,53 @@ private fun InfoColumn(
             rest = rest.substringAfter(match.value)
         }
         append(rest)
+    }
+
+    val descFocus = remember { FocusRequester() }
+    val firstLinkFocus = remember { FocusRequester() }
+    // Focus the description so the D-pad can scroll it right away (issue #23):
+    // a description with no links used to have nothing focusable, so a long
+    // text could never be scrolled down with the remote. Fall back to the
+    // first link when there is no description text.
+    LaunchedEffect(Unit) {
+        kotlinx.coroutines.delay(150)
+        runCatching {
+            if (description.isNotBlank()) descFocus.requestFocus()
+            else firstLinkFocus.requestFocus()
+        }
+    }
+
+    Column(Modifier.fillMaxSize()) {
+        if (description.isNotBlank()) {
+            DescriptionScroll(
+                annotated = annotated,
+                focusRequester = descFocus,
+                onDismiss = onDismiss,
+                onLeaveBottom = {
+                    if (links.isNotEmpty()) {
+                        runCatching { firstLinkFocus.requestFocus() }.isSuccess
+                    } else false
                 },
-                    color = TextMain,
-                    style = MaterialTheme.typography.bodyMedium,
-                    modifier = Modifier.padding(horizontal = 20.dp, vertical = 6.dp),
+                modifier = Modifier.weight(1f, fill = false),
             )
         }
-        }
         if (links.isNotEmpty()) {
-            item(key = "linkshdr") {
             Text(
                 text = "Links",
                 color = TextDim,
                 style = MaterialTheme.typography.labelMedium,
                 modifier = Modifier.padding(start = 20.dp, top = 10.dp, bottom = 2.dp),
             )
-            }
+            LazyColumn(Modifier.heightIn(max = 220.dp)) {
                 links.forEachIndexed { index, url ->
                     item(key = "l" + index + url) {
                         SidebarRow(
                             onLeft = onDismiss,
+                            onUp = if (index == 0 && description.isNotBlank()) {
+                                { runCatching { descFocus.requestFocus() } }
+                            } else null,
+                            atTop = index == 0 && description.isBlank(),
+                            atBottom = index == links.size - 1,
                             focusRequester = if (index == 0) firstLinkFocus else null,
                             onClick = { open(url) },
                         ) {
@@ -228,6 +248,65 @@ private fun InfoColumn(
                 }
             }
         }
+    }
+}
+
+/**
+ * Focusable, D-pad-scrollable description (issue #23). On TV a plain Text in a
+ * LazyColumn can't be scrolled with the remote — nothing in it takes focus — so
+ * long descriptions were unreadable past the first screenful. This box takes
+ * focus and scrolls on UP/DOWN; LEFT closes the panel; DOWN at the bottom hands
+ * focus to the link list (if any).
+ */
+@Composable
+private fun DescriptionScroll(
+    annotated: androidx.compose.ui.text.AnnotatedString,
+    focusRequester: FocusRequester,
+    onDismiss: () -> Unit,
+    onLeaveBottom: () -> Boolean,
+    modifier: Modifier = Modifier,
+) {
+    val scroll = androidx.compose.foundation.rememberScrollState()
+    val scope = rememberCoroutineScope()
+    var focused by remember { mutableStateOf(false) }
+    var viewportPx by remember { mutableStateOf(0) }
+    Box(
+        modifier
+            .fillMaxWidth()
+            .onFocusChanged { focused = it.isFocused }
+            .focusRequester(focusRequester)
+            .focusable()
+            .background(if (focused) Color(0x0DFFFFFF) else Color.Transparent)
+            .onPreviewKeyEvent { ke ->
+                if (ke.type != KeyEventType.KeyDown) return@onPreviewKeyEvent false
+                val step = (viewportPx * 0.85f).coerceAtLeast(240f)
+                when (ke.nativeKeyEvent.keyCode) {
+                    KeyEvent.KEYCODE_DPAD_DOWN ->
+                        if (scroll.value < scroll.maxValue) {
+                            scope.launch { scroll.animateScrollBy(step) }
+                            true
+                        } else onLeaveBottom()
+                    KeyEvent.KEYCODE_DPAD_UP ->
+                        if (scroll.value > 0) {
+                            scope.launch { scroll.animateScrollBy(-step) }
+                            true
+                        } else true // nothing above the description; stay put
+                    KeyEvent.KEYCODE_DPAD_LEFT -> {
+                        onDismiss(); true
+                    }
+                    else -> false
+                }
+            }
+            .verticalScroll(scroll)
+            .onSizeChanged { viewportPx = it.height },
+    ) {
+        Text(
+            text = annotated,
+            color = TextMain,
+            style = MaterialTheme.typography.bodyMedium,
+            modifier = Modifier.padding(horizontal = 20.dp, vertical = 6.dp),
+        )
+    }
 }
 
 /** Link click listener: the annotation callback shape. */