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⚡ Bolt: [performance improvement] Optimize LazyVerticalGrid items composition #9

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⚡ Bolt: [performance improvement] Optimize LazyVerticalGrid items composition #9

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Expand Up @@ -3,3 +3,6 @@
## 2024-05-24 - O(N) Iteration in Cache Size Calculation
**Learning:** Calculating dynamic capacity dynamically via `store.values.sumOf { it.sizeBytes }` effectively incurs an O(N) cost on every `put` because it runs when `trimToCapacity()` calls `dynamicCapacity`. When cache sizes get large, this causes O(N²) overall insertion performance and UI stutters.
**Action:** Use an `AtomicLong` (O(1)) to track the running sum of cache size instead of dynamically iterating through the entire collection.
## 2023-10-05 - [Compose LazyList Performance]
**Learning:** Using `indexOf(item)` inside Compose `items()` loops in a `LazyVerticalGrid` or `LazyColumn` causes unnecessary O(N) operations during recomposition, which leads to dropped frames and laggy scrolling, especially for large lists.
**Action:** Always use `itemsIndexed()` when the index is needed inside the `item` block to provide an O(1) index lookup and ensure smooth scrolling performance.
10 changes: 6 additions & 4 deletions app/src/main/java/com/example/reddittube/ui/main/HomeScreen.kt
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Expand Up @@ -629,11 +629,13 @@ private fun BrowseGrid(
horizontalArrangement = Arrangement.spacedBy(10.dp),
verticalArrangement = Arrangement.spacedBy(10.dp)
) {
items(
// ⚡ Bolt: Performance optimization
// Impact: Prevents O(N) lookup (indexOf) for every visible item during composition by using itemsIndexed.
// Measurement: Scrolling through large feed lists will be noticeably smoother with fewer dropped frames.
itemsIndexed(
items = distinctData,
key = { post -> post.id }
) { post ->
val index = distinctData.indexOf(post).coerceAtLeast(0)
key = { _, post -> post.id }
) { index, post ->
VideoCard(
post = post,
isLiked = likedIds.contains(post.id),
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1 change: 0 additions & 1 deletion app/src/main/java/com/example/reddittube/ui/main/components/MinimalButton.kt
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Expand Up @@ -16,7 +16,6 @@ import androidx.compose.ui.draw.clip
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

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