Add a comment, rename const

packages/block-editor/src/components/list-view/branch.js

@@ -128,7 +128,7 @@ function ListViewBranch( props ) {
 	// The appender means an extra row in List View, so add 1 to the row count.
 	const rowCount = showAppender ? blockCount + 1 : blockCount;
 	let nextPosition = listPosition;
-	const singleBlockSelection = selectedClientIds?.length === 1;
+	const isSingleBlockSelection = selectedClientIds?.length === 1;
 
 	return (
 		<>
@@ -169,11 +169,18 @@ function ListViewBranch( props ) {
 				);
 				const isSelectedBranch =
 					isBranchSelected || ( isSelected && hasNestedBlocks );
+
+				// To avoid performance issues, we only render blocks that are
+				// in view, or blocks that are selected or dragged.
+				// If a block is selected, it is only counted if it is the only
+				// block selected. This prevents the entire tree from being
+				// rendered when a branch is selected, or a user selects all blocks,
+				// while still enabling scroll into view behavior when selecting a block.
 				const showBlock =
 					isDragged ||
 					blockInView ||
 					isBranchDragged ||
-					( isSelected && singleBlockSelection );
+					( isSelected && isSingleBlockSelection );
 				return (
 					<AsyncModeProvider key={ clientId } value={ ! isSelected }>
 						{ showBlock && (