From 0d6651b0da19e7ea9be1969399298f4f0591d707 Mon Sep 17 00:00:00 2001
From: Apoorv Mishra <apoorvmishra101092@gmail.com>
Date: Fri, 3 Feb 2023 09:41:24 +0530
Subject: [PATCH] Scroll children into view upon expansion (#4812)

* feat: smoothly scroll children into view

* fix: disable smooth scroll and throttling
---
 app/components/DocumentExplorer.tsx     | 32 +++++++++++++++++-
 app/components/DocumentExplorerNode.tsx | 45 ++++++++++---------------
 2 files changed, 48 insertions(+), 29 deletions(-)

diff --git a/app/components/DocumentExplorer.tsx b/app/components/DocumentExplorer.tsx
index c2df49ad4..82b0ab1cb 100644
--- a/app/components/DocumentExplorer.tsx
+++ b/app/components/DocumentExplorer.tsx
@@ -1,11 +1,12 @@
 import FuzzySearch from "fuzzy-search";
-import { includes, difference, concat, filter } from "lodash";
+import { includes, difference, concat, filter, map, fill } from "lodash";
 import { observer } from "mobx-react";
 import { StarredIcon, DocumentIcon } from "outline-icons";
 import * as React from "react";
 import { useTranslation } from "react-i18next";
 import AutoSizer from "react-virtualized-auto-sizer";
 import { FixedSizeList as List } from "react-window";
+import scrollIntoView from "smooth-scroll-into-view-if-needed";
 import styled, { useTheme } from "styled-components";
 import breakpoint from "styled-components-breakpoint";
 import { NavigationNode } from "@shared/types";
@@ -50,6 +51,9 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
   const [nodes, setNodes] = React.useState<NavigationNode[]>([]);
   const [activeNode, setActiveNode] = React.useState<number>(0);
   const [expandedNodes, setExpandedNodes] = React.useState<string[]>([]);
+  const [itemRefs, setItemRefs] = React.useState<
+    React.RefObject<HTMLSpanElement>[]
+  >([]);
 
   const inputSearchRef = React.useRef<HTMLInputElement | HTMLTextAreaElement>(
     null
@@ -86,10 +90,31 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
     setNodes(results);
   }, [searchTerm, items, searchIndex]);
 
+  React.useEffect(() => {
+    setItemRefs((itemRefs) =>
+      map(
+        fill(Array(items.length), 0),
+        (_, i) => itemRefs[i] || React.createRef()
+      )
+    );
+  }, [items.length]);
+
   React.useEffect(() => {
     onSelect(selectedNode);
   }, [selectedNode, onSelect]);
 
+  const scrollNodeIntoView = React.useCallback(
+    (node: number) => {
+      if (itemRefs[node] && itemRefs[node].current) {
+        scrollIntoView(itemRefs[node].current as HTMLSpanElement, {
+          behavior: "auto",
+          block: "center",
+        });
+      }
+    },
+    [itemRefs]
+  );
+
   const handleSearch = (ev: React.ChangeEvent<HTMLInputElement>) => {
     setSearchTerm(ev.target.value);
   };
@@ -241,6 +266,7 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
         title={title}
         depth={node.depth as number}
         hasChildren={hasChildren(index)}
+        ref={itemRefs[index]}
       />
     );
   };
@@ -262,6 +288,7 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
       case "ArrowDown": {
         ev.preventDefault();
         setActiveNode(next());
+        scrollNodeIntoView(next());
         break;
       }
       case "ArrowUp": {
@@ -270,6 +297,7 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
           focusSearchInput();
         } else {
           setActiveNode(prev());
+          scrollNodeIntoView(prev());
         }
         break;
       }
@@ -282,6 +310,8 @@ function DocumentExplorer({ onSubmit, onSelect, items }: Props) {
       case "ArrowRight": {
         if (!searchTerm) {
           toggleCollapse(activeNode);
+          // let the nodes re-render first and then scroll
+          setImmediate(() => scrollNodeIntoView(activeNode));
         }
         break;
       }
diff --git a/app/components/DocumentExplorerNode.tsx b/app/components/DocumentExplorerNode.tsx
index e3eb6bfd7..1431661b9 100644
--- a/app/components/DocumentExplorerNode.tsx
+++ b/app/components/DocumentExplorerNode.tsx
@@ -1,7 +1,6 @@
 import { observer } from "mobx-react";
 import * as React from "react";
 import { useTranslation } from "react-i18next";
-import scrollIntoView from "smooth-scroll-into-view-if-needed";
 import styled from "styled-components";
 import breakpoint from "styled-components-breakpoint";
 import Flex from "~/components/Flex";
@@ -23,38 +22,28 @@ type Props = {
   onClick: (ev: React.MouseEvent) => void;
 };
 
-function DocumentExplorerNode({
-  selected,
-  active,
-  style,
-  expanded,
-  icon,
-  title,
-  depth,
-  hasChildren,
-  onDisclosureClick,
-  onPointerMove,
-  onClick,
-}: Props) {
+function DocumentExplorerNode(
+  {
+    selected,
+    active,
+    style,
+    expanded,
+    icon,
+    title,
+    depth,
+    hasChildren,
+    onDisclosureClick,
+    onPointerMove,
+    onClick,
+  }: Props,
+  ref: React.RefObject<HTMLSpanElement>
+) {
   const { t } = useTranslation();
   const OFFSET = 12;
   const ICON_SIZE = 24;
 
   const width = depth ? depth * ICON_SIZE + OFFSET : ICON_SIZE;
 
-  const ref = React.useCallback(
-    (node: HTMLSpanElement | null) => {
-      if (active && node) {
-        scrollIntoView(node, {
-          scrollMode: "if-needed",
-          behavior: "auto",
-          block: "nearest",
-        });
-      }
-    },
-    [active]
-  );
-
   return (
     <Node
       ref={ref}
@@ -142,4 +131,4 @@ export const Node = styled.span<{
   `}
 `;
 
-export default observer(DocumentExplorerNode);
+export default observer(React.forwardRef(DocumentExplorerNode));