List View: render a fixed number of items

bin/plugin/commands/performance.js

@@ -40,6 +40,7 @@ const config = require( '../config' );
  * @property {number[]} inserterOpen         Average time to open global inserter.
  * @property {number[]} inserterSearch       Average time to search the inserter.
  * @property {number[]} inserterHover        Average time to move mouse between two block item in the inserter.
+ * @property {number[]} listViewOpen         Average time to open listView
  */
 
 /**
@@ -52,7 +53,7 @@ const config = require( '../config' );
  * @property {number=} firstContentfulPaint Represents the time when the browser first renders any text or media.
  * @property {number=} firstBlock           Represents the time when Puppeteer first sees a block selector in the DOM.
  * @property {number=} type                 Average type time.
- * @property {number=} minType              Minium type time.
+ * @property {number=} minType              Minimum type time.
  * @property {number=} maxType              Maximum type time.
  * @property {number=} focus                Average block selection time.
  * @property {number=} minFocus             Min block selection time.
@@ -66,6 +67,9 @@ const config = require( '../config' );
  * @property {number=} inserterHover        Average time to move mouse between two block item in the inserter.
  * @property {number=} minInserterHover     Min time to move mouse between two block item in the inserter.
  * @property {number=} maxInserterHover     Max time to move mouse between two block item in the inserter.
+ * @property {number=} listViewOpen         Average time to open list view.
+ * @property {number=} minListViewOpen      Min time to open list view.
+ * @property {number=} maxListViewOpen      Max time to open list view.
  */
 
 /**
@@ -136,6 +140,9 @@ function curateResults( results ) {
 		inserterHover: average( results.inserterHover ),
 		minInserterHover: Math.min( ...results.inserterHover ),
 		maxInserterHover: Math.max( ...results.inserterHover ),
+		listViewOpen: average( results.listViewOpen ),
+		minListViewOpen: Math.min( ...results.listViewOpen ),
+		maxListViewOpen: Math.max( ...results.listViewOpen ),
 	};
 }
 
@@ -378,6 +385,15 @@ async function runPerformanceTests( branches, options ) {
 					maxInserterHover: rawResults.map(
 						( r ) => r[ branch ].maxInserterHover
 					),
+					listViewOpen: rawResults.map(
+						( r ) => r[ branch ].listViewOpen
+					),
+					minListViewOpen: rawResults.map(
+						( r ) => r[ branch ].minListViewOpen
+					),
+					maxListViewOpen: rawResults.map(
+						( r ) => r[ branch ].maxListViewOpen
+					),
 				},
 				median
 			);

packages/block-editor/CHANGELOG.md

@@ -4,7 +4,8 @@
 
 ### Performance
 
--   Avoid re-rendering all List View items on block focus [#35706](https://github.com/WordPress/gutenberg/pull/35706). These changes speed up block focus time in large posts by 80% when List View is open.
+-   Avoid re-rendering all List View items on block focus [#35706](https://github.com/WordPress/gutenberg/pull/35706). When List View is open Block focus time is 4 times faster in large posts.
+-   Render fixed number of items in List View [#35706](https://github.com/WordPress/gutenberg/pull/35230). Opening List View is 13 times faster in large posts.
 
 ### Breaking change
 

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

@@ -1,41 +1,94 @@
 /**
  * External dependencies
  */
-import { map, compact } from 'lodash';
+import { compact } from 'lodash';
 
 /**
  * WordPress dependencies
  */
-import { Fragment } from '@wordpress/element';
+import { Fragment, memo } from '@wordpress/element';
 
 /**
  * Internal dependencies
  */
 import ListViewBlock from './block';
 import { useListViewContext } from './context';
 
-export default function ListViewBranch( props ) {
+function countBlocks( block, expandedState, draggedClientIds ) {
+	const isDragged = draggedClientIds?.includes( block.clientId );
+	if ( isDragged ) {
+		return 0;
+	}
+	const isExpanded = expandedState[ block.clientId ] ?? true;
+	if ( isExpanded ) {
+		return (
+			1 +
+			block.innerBlocks.reduce(
+				countReducer( expandedState, draggedClientIds ),
+				0
+			)
+		);
+	}
+	return 1;
+}
+const countReducer = ( expandedState, draggedClientIds ) => (
+	count,
+	block
+) => {
+	const isDragged = draggedClientIds?.includes( block.clientId );
+	if ( isDragged ) {
+		return count;
+	}
+	const isExpanded = expandedState[ block.clientId ] ?? true;
+	if ( isExpanded && block.innerBlocks.length > 0 ) {
+		return count + countBlocks( block, expandedState, draggedClientIds );
+	}
+	return count + 1;
+};
+
+function ListViewBranch( props ) {
 	const {
 		blocks,
 		selectBlock,
 		showBlockMovers,
 		showNestedBlocks,
 		level = 1,
 		path = '',
+		listPosition = 0,
+		fixedListWindow,
 	} = props;
 
-	const { expandedState, draggedClientIds } = useListViewContext();
+	const {
+		expandedState,
+		draggedClientIds,
+		__experimentalPersistentListViewFeatures,
+	} = useListViewContext();
 
 	const filteredBlocks = compact( blocks );
 	const blockCount = filteredBlocks.length;
+	let nextPosition = listPosition;
 
 	return (
 		<>
-			{ map( filteredBlocks, ( block, index ) => {
+			{ filteredBlocks.map( ( block, index ) => {
 				const { clientId, innerBlocks } = block;
+
+				if ( index > 0 ) {
+					nextPosition += countBlocks(
+						filteredBlocks[ index - 1 ],
+						expandedState,
+						draggedClientIds
+					);
+				}
+
+				const usesWindowing = __experimentalPersistentListViewFeatures;
+
+				const { itemInView } = fixedListWindow;
+
+				const blockInView =
+					! usesWindowing || itemInView( nextPosition );
+
 				const position = index + 1;
-				// This string value is used to trigger an animation change.
-				// This may be removed if we use a different animation library in the future.
 				const updatedPath =
 					path.length > 0
 						? `${ path }_${ position }`
@@ -49,20 +102,29 @@ export default function ListViewBranch( props ) {
 
 				const isDragged = !! draggedClientIds?.includes( clientId );
 
+				const showBlock = isDragged || blockInView;
 				return (
 					<Fragment key={ clientId }>
-						<ListViewBlock
-							block={ block }
-							selectBlock={ selectBlock }
-							isDragged={ isDragged }
-							level={ level }
-							position={ position }
-							rowCount={ blockCount }
-							siblingBlockCount={ blockCount }
-							showBlockMovers={ showBlockMovers }
-							path={ updatedPath }
-							isExpanded={ isExpanded }
-						/>
+						{ showBlock && (
+							<ListViewBlock
+								block={ block }
+								selectBlock={ selectBlock }
+								isDragged={ isDragged }
+								level={ level }
+								position={ position }
+								rowCount={ blockCount }
+								siblingBlockCount={ blockCount }
+								showBlockMovers={ showBlockMovers }
+								path={ updatedPath }
+								isExpanded={ isExpanded }
+								listPosition={ nextPosition }
+							/>
+						) }
+						{ ! showBlock && (
+							<tr>
+								<td className="block-editor-list-view-placeholder" />
+							</tr>
+						) }
 						{ hasNestedBlocks && isExpanded && ! isDragged && (
 							<ListViewBranch
 								blocks={ innerBlocks }
@@ -71,6 +133,8 @@ export default function ListViewBranch( props ) {
 								showNestedBlocks={ showNestedBlocks }
 								level={ level + 1 }
 								path={ updatedPath }
+								listPosition={ nextPosition + 1 }
+								fixedListWindow={ fixedListWindow }
 							/>
 						) }
 					</Fragment>
@@ -83,3 +147,5 @@ export default function ListViewBranch( props ) {
 ListViewBranch.defaultProps = {
 	selectBlock: () => {},
 };
+
+export default memo( ListViewBranch );

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

@@ -1,10 +1,12 @@
 /**
  * WordPress dependencies
  */
-
-import { useMergeRefs } from '@wordpress/compose';
+import {
+	useMergeRefs,
+	__experimentalUseFixedWindowList as useFixedWindowList,
+} from '@wordpress/compose';
 import { __experimentalTreeGrid as TreeGrid } from '@wordpress/components';
-import { AsyncModeProvider, useDispatch } from '@wordpress/data';
+import { AsyncModeProvider, useDispatch, useSelect } from '@wordpress/data';
 import {
 	useCallback,
 	useEffect,
@@ -67,6 +69,21 @@ function ListView(
 ) {
 	const { clientIdsTree, draggedClientIds } = useListViewClientIds( blocks );
 	const { selectBlock } = useDispatch( blockEditorStore );
+	const { visibleBlockCount } = useSelect(
+		( select ) => {
+			const { getGlobalBlockCount, getClientIdsOfDescendants } = select(
+				blockEditorStore
+			);
+			const draggedBlockCount =
+				draggedClientIds?.length > 0
+					? getClientIdsOfDescendants( draggedClientIds ).length + 1
+					: 0;
+			return {
+				visibleBlockCount: getGlobalBlockCount() - draggedBlockCount,
+			};
+		},
+		[ draggedClientIds ]
+	);
 	const selectEditorBlock = useCallback(
 		( clientId ) => {
 			selectBlock( clientId );
@@ -85,6 +102,15 @@ function ListView(
 		isMounted.current = true;
 	}, [] );
 
+	const [ fixedListWindow ] = useFixedWindowList(
+		elementRef,
+		36,
+		visibleBlockCount,
+		{
+			useWindowing: __experimentalPersistentListViewFeatures,
+		}
+	);
+
 	const expand = useCallback(
 		( clientId ) => {
 			if ( ! clientId ) {
@@ -158,6 +184,7 @@ function ListView(
 						selectBlock={ selectEditorBlock }
 						showNestedBlocks={ showNestedBlocks }
 						showBlockMovers={ showBlockMovers }
+						fixedListWindow={ fixedListWindow }
 						{ ...props }
 					/>
 				</ListViewContext.Provider>

packages/block-editor/src/components/list-view/style.scss

@@ -357,3 +357,9 @@ $block-navigation-max-indent: 8;
 	box-shadow: none;
 }
 
+.block-editor-list-view-placeholder {
+	padding: 0;
+	margin: 0;
+	height: 36px;
+}
+