From 5aa20b99f370213c141b639bc613778d933a0dd1 Mon Sep 17 00:00:00 2001
From: Josefina Mancilla <32556167+jnm2377@users.noreply.github.com>
Date: Tue, 19 May 2020 09:10:51 -0500
Subject: [PATCH] fix: left nav duplicate active selection and jumping scroll
 (#819)

* v1.17.2

* v1.17.3

* fix: left nav is active bug and jumping scroll

* fix: query selector classname

* chore: add testing example

* chore: comments

* fix: update scollOffset name

* fix: tweak hooks logic

* fix: remove hook reference

* fix: only set scroll top when it isn't defined

* fix: remove nav context scroll function

* fix: remove testing pages

Co-authored-by: Vince Picone <vpicone@gmail.com>
Co-authored-by: Scott Strubberg <sstrubberg@protonmail.com>
Co-authored-by: Vince Picone <Vincent.Patrick.Picone@ibm.com>
---
 .../src/components/LeftNav/LeftNav.js         | 28 +++++++++++++++++--
 .../src/components/LeftNav/LeftNavItem.js     | 10 +++----
 .../src/util/context/NavContext.js            |  8 +++++-
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNav.js b/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNav.js
index 032062eb8..f96a360c3 100644
--- a/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNav.js
+++ b/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNav.js
@@ -1,4 +1,4 @@
-import React, { useContext } from 'react';
+import React, { useContext, useRef, useEffect } from 'react';
 import classnames from 'classnames';
 import { SideNav, SideNavItems } from 'carbon-components-react';
 import { useNavItems } from './LeftNavItemProvider';
@@ -11,7 +11,28 @@ import LeftNavWrapper from './LeftNavWrapper';
 import { sideNavDark } from './LeftNav.module.scss';
 
 const LeftNav = (props) => {
-  const { leftNavIsOpen } = useContext(NavContext);
+  const { leftNavIsOpen, leftNavScrollTop, setLeftNavScrollTop } = useContext(
+    NavContext
+  );
+
+  const sideNavRef = useRef();
+  const sideNavListRef = useRef();
+
+  useEffect(() => {
+    sideNavListRef.current = sideNavRef.current.querySelector('.sidenav-list');
+  }, []);
+
+  useEffect(() => {
+    sideNavListRef.current.addEventListener('scroll', (e) => {
+      setLeftNavScrollTop(e.target.scrollTop);
+    });
+  }, [setLeftNavScrollTop]);
+
+  useEffect(() => {
+    if (leftNavScrollTop >= 0 && !sideNavListRef?.current.scrollTop) {
+      sideNavListRef.current.scrollTop = leftNavScrollTop;
+    }
+  }, [leftNavScrollTop]);
 
   const navItems = useNavItems();
 
@@ -19,6 +40,7 @@ const LeftNav = (props) => {
   return (
     <LeftNavWrapper expanded={leftNavIsOpen}>
       <SideNav
+        ref={sideNavRef}
         expanded
         defaultExpanded
         aria-label="Side navigation"
@@ -31,7 +53,7 @@ const LeftNav = (props) => {
             props.theme !== 'dark' && !props.homepage,
         })}
       >
-        <SideNavItems>
+        <SideNavItems className="sidenav-list">
           {navItems.map((item, i) => (
             <LeftNavItem items={item.pages} category={item.title} key={i} />
           ))}
diff --git a/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNavItem.js b/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNavItem.js
index 324a13281..b83826d8f 100644
--- a/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNavItem.js
+++ b/packages/gatsby-theme-carbon/src/components/LeftNav/LeftNavItem.js
@@ -16,7 +16,9 @@ import usePathprefix from '../../util/hooks/usePathprefix';
 const LeftNavItem = (props) => {
   const { items, category } = props;
   const { toggleNavState } = useContext(NavContext);
-  const closeLeftNav = () => toggleNavState('leftNavIsOpen', 'close');
+  const closeLeftNav = () => {
+    toggleNavState('leftNavIsOpen', 'close');
+  };
   const pathPrefix = usePathprefix();
 
   return (
@@ -66,10 +68,8 @@ const LeftNavItem = (props) => {
 const SubNavItems = ({ items, pathname, onClick }) =>
   items.map((item, i) => {
     const hasActiveTab =
-      item.path.split('/') > 3
-        ? item.path.split('/')[3] === pathname.split('/')[3]
-        : item.path.split('/')[2] === pathname.split('/')[2];
-
+      `${item.path.split('/')[1]}/${item.path.split('/')[2]}` ===
+      `${pathname.split('/')[1]}/${pathname.split('/')[2]}`;
     return (
       <SideNavMenuItem
         to={`${item.path}`}
diff --git a/packages/gatsby-theme-carbon/src/util/context/NavContext.js b/packages/gatsby-theme-carbon/src/util/context/NavContext.js
index e889d5934..2fdd9c07b 100644
--- a/packages/gatsby-theme-carbon/src/util/context/NavContext.js
+++ b/packages/gatsby-theme-carbon/src/util/context/NavContext.js
@@ -5,6 +5,7 @@ const NavContext = React.createContext({
   searchIsOpen: false,
   switcherIsOpen: false,
   isManagingFocus: false,
+  leftNavScrollOffset: 0,
 });
 
 const reducer = (state, action) => {
@@ -19,7 +20,7 @@ const reducer = (state, action) => {
 };
 export const NavContextProvider = ({ children }) => {
   const [
-    { leftNavIsOpen, searchIsOpen, switcherIsOpen },
+    { leftNavIsOpen, searchIsOpen, switcherIsOpen, leftNavScrollOffset },
     dispatch,
   ] = useReducer(reducer, {
     leftNavIsOpen: false,
@@ -27,6 +28,8 @@ export const NavContextProvider = ({ children }) => {
     switcherIsOpen: false,
   });
 
+  const [leftNavScrollTop, setLeftNavScrollTop] = useState(0);
+
   const toggleNavState = (nav, type) => {
     dispatch({ nav, type });
   };
@@ -40,6 +43,9 @@ export const NavContextProvider = ({ children }) => {
     toggleNavState,
     isManagingFocus,
     setIsManagingFocus,
+    leftNavScrollOffset,
+    leftNavScrollTop,
+    setLeftNavScrollTop,
   };
 
   return <NavContext.Provider value={value}>{children}</NavContext.Provider>;