kototoro-browse-source-scroll

name	kototoro-browse-source-scroll
description	Diagnose and fix Kototoro Browse/Explore page content source scrolling jank when many sources exist. Use for ExploreHostScreen, ExploreViewModel, source quick access, LazyColumn source rows, source grouping, browse recommendation loading, and tab switching performance.

Kototoro Browse Source Scroll

Use this skill when the Browse/Explore page stalls, freezes, or shows a blank frame while switching to the sources area, especially with hundreds or thousands of installed/enabled sources.

Root Cause Pattern

Do not treat this as only an image/icon loading problem. In Kototoro the expensive path can be:

• Rendering all sources inside one large composable block.
• Grouping/chunking sources during every recomposition.
• Showing source quick access fully expanded while tracking recommendation hero content is also present.
• Mixing discover recommendation loading state with source loading state.
• Recreating source rows on every tab/filter change because keys/content types are too coarse.

Preferred Fix Pattern

• Split source quick access into LazyListScope items instead of a single detached block.
• Render source cards as lazy rows with stable row keys and contentType.
• Precompute source metrics with remember(gridScale).
• Precompute groups with remember(sources, isGroupedByLanguage, context).
• Default to a collapsed source section when recommendations are enabled; expand only on user request.
• Force expanded only when recommendations are disabled, so source-only mode preserves the old direct-access behavior.
• Track source loading separately from discover/recommendation loading.

Implementation Checklist

• Add a BrowseSourceItems.isLoadingOnly or equivalent source-specific loading state.
• Keep recommendation loading in a separate isDiscoverLoadingOnly.
• Compute sourceColumns from list mode and metrics.
• Use a small collapsed count such as columns * 5.
• Build visibleSourceGroups with a max source count.
• Use itemsIndexed rows:

itemsIndexed(
    items = rows,
    key = { rowIndex, rowSources ->
        val firstId = rowSources.firstOrNull()?.id ?: rowIndex.toLong()
        "source_row_${groupIndex}_${rowIndex}_$firstId"
    },
    contentType = { _, _ -> "source_row" },
) { _, rowSources ->
    SourceQuickAccessRow(...)
}

Pitfalls

• Do not put a large nested source grid inside one item if the page itself is a LazyColumn.
• Do not use only index keys for source rows if groups can change.
• Do not let disabled recommendation features still trigger recommendation load or refresh.
• Do not remove source long-click selection behavior while refactoring rows.

Verification

Run:

JAVA_HOME="/usr/lib/jvm/java-17-openjdk-amd64" ./gradlew :app:compileDebugKotlin --no-daemon

Manual acceptance:

• Switching to Browse with many sources does not pause before first paint.
• Scrolling remains responsive with hundreds or thousands of sources.
• "Show more/less" works and preserves source click/long-click behavior.
• Source-only mode still shows all sources without hiding access behind recommendations.