player: scroll the info text in thirds of a screen (#23)

One D-pad press moved 85% of the panel, so consecutive stops barely overlapped
and the middle of a long description was never on screen — on
tube.jeena.net/w/p4HtZrDCMbPfGYpMfG9fMN Jeena could not read the passage about
the credit-card outlier at all (#23 review). A press now moves about a third of
a screenful, so each stop repeats two thirds of the previous one and every line
gets shown on the way down.

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

@@ -245,7 +245,11 @@ private fun DescriptionScroll(
             .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)
+                // One press moves a third of a screenful, so consecutive stops
+                // overlap and every line of a long description gets shown (issue
+                // #23 review: the old 85% step jumped past the middle of the text
+                // on tube.jeena.net/w/p4HtZrDCMbPfGYpMfG9fMN).
+                val step = (viewportPx * 0.34f).coerceAtLeast(150f)
                 val code = ke.nativeKeyEvent.keyCode
                 // Match Compose's normalised key AND the raw keycode: remotes don't all
                 // report the same native codes, and matching only the raw one left UP

app/src/main/java/net/jeena/jtubetv/ui/screens/ChannelsScreen.kt

@@ -358,6 +358,14 @@ fun ChannelsScreen(
             // as stats stream in the rows re-sort, and re-focusing their first card
             // would steal focus mid-navigation (user: "up jumps to the first row").
             val focusHandedOut = remember { mutableStateOf(false) }
+            // The channel we came back from only wins the focus while it is still
+            // in the rows. When it isn't (renamed, unsubscribed, or the rows simply
+            // never carried it) every row used to ask for no focus at all — "when I
+            // click on Channels, none is selected" (#32 review). Fall back to the
+            // first row in that case, like the video cards do.
+            val focusRowExists = focusHandle != null && viewModel.userRows.any {
+                group -> group.channels.any { it.name + "@" + it.host == focusHandle }
+            }
             LazyColumn(Modifier.fillMaxSize()) {
                 viewModel.userRows.forEach { group ->
                     item(key = "hdr-" + group.ownerName) {
@@ -379,7 +387,7 @@ fun ChannelsScreen(
                             onOpenDrawer,
                             drawerPulse = drawerPulse,
                             focused = !focusHandedOut.value && (
-                                if (focusHandle != null) isTargetRow
+                                if (focusRowExists) isTargetRow
                                 else group == viewModel.userRows.firstOrNull()
                             ),
                             focusIndex = if (isTargetRow) target else 0,
@@ -479,6 +487,11 @@ private fun ChannelRow(
                         return@LaunchedEffect
                     }
                 }
+                // The wanted card never became focusable (its row scrolled past it,
+                // or the handle went stale): take the first card instead, so the
+                // screen is never left with nothing selected (#32 review).
+                val first = focusRequesters[0]
+                if (first != null && runCatching { first.requestFocus() }.isSuccess) onFocused()
             }
         }
     }

app/src/main/java/net/jeena/jtubetv/ui/screens/list/VideoListScreen.kt

@@ -78,6 +78,29 @@ fun VideoListScreen(
     val requesters = androidx.compose.runtime.remember(items.size, epoch) {
         androidx.compose.runtime.mutableStateMapOf<Int, FocusRequester>()
     }
+    // Scroll position survives destination switches (per source), not just player exits.
+    val gridState = androidx.compose.runtime.saveable.rememberSaveable(
+        inputs = arrayOf(epoch),
+        key = "g$epoch:" + sourceKey(source), saver = androidx.compose.foundation.lazy.grid.LazyGridState.Saver,
+    ) { androidx.compose.foundation.lazy.grid.LazyGridState() }
+
+    if (source is ListSource.Channel) {
+        // Fetch the banner/avatar/counts for the channel page header.
+        LaunchedEffect(source) { viewModel.loadChannelHeader(AppGraph.repository) }
+        // Park the grid at the top as soon as the page has content, BEFORE the
+        // first card takes focus (the effect below). It used to run after it:
+        // handing the first card the focus animates the grid up (a focused card
+        // that sits partly off-screen is pulled into view), and this effect then
+        // snapped it back down — the jump that was still reported on the channel
+        // page when the first video got focus (#27 review). Doing the park first,
+        // and only while the grid is actually displaced, leaves nothing to undo.
+        LaunchedEffect(items.isNotEmpty(), source) {
+            if (items.isNotEmpty() && gridState.firstVisibleItemIndex > 0) {
+                runCatching { gridState.scrollToItem(0) }
+            }
+        }
+    }
+
     // Pull initial focus out of the sidebar rail and into the content grid.
     val initialFocus = remember { FocusRequester() }
     // Which card was opened last — re-focus it when playback ends (UX report BUG-3).
@@ -86,6 +109,9 @@ fun VideoListScreen(
         // With a running search the first RESULT gets focus; without one the
         // field does (the SearchHeader's own effect) — never both (issue #20).
         if (items.isNotEmpty() && (source !is ListSource.Search || viewModel.searchActive)) {
+            // The channel page parks its grid at the top just above; wait for that
+            // beat so the focus handover can never leave a scroll to undo (#27).
+            if (source is ListSource.Channel) kotlinx.coroutines.delay(250)
             runCatching { requesters[0]?.requestFocus() ?: initialFocus.requestFocus() }
         }
     }
@@ -100,26 +126,6 @@ fun VideoListScreen(
             lastOpenedIndex = -1
         }
     }
-    // Scroll position survives destination switches (per source), not just player exits.
-    val gridState = androidx.compose.runtime.saveable.rememberSaveable(
-        inputs = arrayOf(epoch),
-        key = "g$epoch:" + sourceKey(source), saver = androidx.compose.foundation.lazy.grid.LazyGridState.Saver,
-    ) { androidx.compose.foundation.lazy.grid.LazyGridState() }
-
-    if (source is ListSource.Channel) {
-        // Fetch the banner/avatar/counts for the channel page header.
-        LaunchedEffect(source) { viewModel.loadChannelHeader(AppGraph.repository) }
-        // Focusing the first card nudges the grid down far enough to clip the
-        // header's top (and its Subscribe button); the header and the first row
-        // both fit, so park the grid back at the top when the page opens.
-        LaunchedEffect(items.isNotEmpty(), source) {
-            if (items.isNotEmpty()) {
-                kotlinx.coroutines.delay(150)
-                runCatching { gridState.scrollToItem(0) }
-            }
-        }
-    }
-
     // Row starts of the grid: LEFT from a row's first card opens the drawer
     // (issue #7). The adaptive columns use a `rowCardWidth() - 12` minimum with
     // zero spacing, and the content pane eats 40dp (8 start + 32 end), so the
@@ -217,7 +223,7 @@ fun VideoListScreen(
             // Placeholder cards while the page's first chunk loads (issue #19):
             // shaped like the real cards, with the faint shimmer, on every
             // VideoListScreen (My videos, Search, Subscriptions, History, channel pages).
-            item(key = "initial-placeholders", span = { androidx.compose.foundation.lazy.grid.GridItemSpan(maxLineSpan) }) {
+            item(key = "initial-placeholders") {
                 LaunchedEffect(source) { viewModel.loadMore(force = true) }
                 // A single loading card, not a full fake grid (issue #31).
                 ShimmerCard(