From 541cfb49192b955212c314f95913d79e32d066dd Mon Sep 17 00:00:00 2001
From: Kerry Liu <kerryliu@gmail.com>
Date: Tue, 5 Oct 2021 14:54:14 -0700
Subject: [PATCH] List View: calculate visible block count when dragging

---
 .../src/components/list-view/branch.js        | 41 ++++++++++++++-----
 .../src/components/list-view/index.js         | 23 ++++++++---
 2 files changed, 48 insertions(+), 16 deletions(-)

diff --git a/packages/block-editor/src/components/list-view/branch.js b/packages/block-editor/src/components/list-view/branch.js
index 2715779dc8d637..aabc22da47f7cf 100644
--- a/packages/block-editor/src/components/list-view/branch.js
+++ b/packages/block-editor/src/components/list-view/branch.js
@@ -16,17 +16,34 @@ import ListViewAppender from './appender';
 import { isClientIdSelected } from './utils';
 import { useListViewContext } from './context';
 
-function countBlocks( block, expandedState ) {
+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 ), 0 );
+		return (
+			1 +
+			block.innerBlocks.reduce(
+				countReducer( expandedState, draggedClientIds ),
+				0
+			)
+		);
 	}
 	return 1;
 }
-const countReducer = ( expandedState ) => ( count, block ) => {
+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 );
+		return count + countBlocks( block, expandedState, draggedClientIds );
 	}
 	return count + 1;
 };
@@ -48,7 +65,7 @@ export default function ListViewBranch( props ) {
 		isLastOfBranch = false,
 		listPosition = 0,
 		windowMeasurement,
-		globalBlockCount,
+		visibleBlockCount,
 	} = props;
 
 	const {
@@ -81,7 +98,8 @@ export default function ListViewBranch( props ) {
 		if ( index > 0 ) {
 			nextPosition += countBlocks(
 				filteredBlocks[ index - 1 ],
-				expandedState
+				expandedState,
+				draggedClientIds
 			);
 		}
 		const { start, maxVisible, focus } = windowMeasurement;
@@ -92,7 +110,8 @@ export default function ListViewBranch( props ) {
 			! __experimentalPersistentListViewFeatures ||
 			( start <= nextPosition && nextPosition <= start + maxVisible );
 
-		if ( ! blockInView && nextPosition > start ) {
+		const isDragging = draggedClientIds?.length > 0;
+		if ( ! isDragging && ! blockInView && nextPosition > start ) {
 			// found the end of the window, don't bother processing the rest of the items
 			break;
 		}
@@ -103,11 +122,11 @@ export default function ListViewBranch( props ) {
 				? { paddingTop: ITEM_HEIGHT * start }
 				: {} ),
 			...( __experimentalPersistentListViewFeatures &&
-			globalBlockCount > end &&
+			visibleBlockCount > end &&
 			end === nextPosition
 				? {
 						paddingBottom:
-							ITEM_HEIGHT * ( globalBlockCount - end - 1 ),
+							ITEM_HEIGHT * ( visibleBlockCount - end - 1 ),
 				  }
 				: {} ),
 		};
@@ -162,7 +181,7 @@ export default function ListViewBranch( props ) {
 
 		listItems.push(
 			<AsyncModeProvider key={ clientId } value={ ! isSelected }>
-				{ blockInView && (
+				{ ( isDragged || blockInView ) && (
 					<ListViewBlock
 						block={ block }
 						onClick={ selectBlockWithClientId }
@@ -199,7 +218,7 @@ export default function ListViewBranch( props ) {
 						path={ updatedPath }
 						listPosition={ nextPosition + 1 }
 						windowMeasurement={ windowMeasurement }
-						globalBlockCount={ globalBlockCount }
+						visibleBlockCount={ visibleBlockCount }
 					/>
 				) }
 			</AsyncModeProvider>
diff --git a/packages/block-editor/src/components/list-view/index.js b/packages/block-editor/src/components/list-view/index.js
index 3530600d398be8..82bd22e9729910 100644
--- a/packages/block-editor/src/components/list-view/index.js
+++ b/packages/block-editor/src/components/list-view/index.js
@@ -95,9 +95,21 @@ function ListView(
 		__experimentalPersistentListViewFeatures
 	);
 
-	const globalBlockCount = useSelect( ( select ) => {
-		return select( blockEditorStore ).getGlobalBlockCount();
-	}, [] );
+	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 { selectBlock } = useDispatch( blockEditorStore );
 	const selectEditorBlock = useCallback(
@@ -193,7 +205,7 @@ function ListView(
 			const { start, maxVisible } = lastMeasurement;
 			const nextStart = Math.min(
 				start + 1,
-				globalBlockCount - maxVisible
+				visibleBlockCount - maxVisible
 			);
 			return {
 				start: nextStart,
@@ -226,6 +238,7 @@ function ListView(
 			collapse,
 		]
 	);
+
 	return (
 		<AsyncModeProvider value={ true }>
 			<ListViewDropIndicator
@@ -246,7 +259,7 @@ function ListView(
 						blocks={ clientIdsTree }
 						selectBlock={ selectEditorBlock }
 						windowMeasurement={ windowMeasurement }
-						globalBlockCount={ globalBlockCount }
+						visibleBlockCount={ visibleBlockCount }
 						{ ...props }
 					/>
 				</ListViewContext.Provider>