From 6e898597e614a97b4a820a6abf2cf9270e901bee Mon Sep 17 00:00:00 2001
From: Felix Habib <fhabib@seek.com.au>
Date: Mon, 9 Sep 2024 15:29:20 +1000
Subject: [PATCH] Improve snippets scrolling behaviour

---
 .changeset/wicked-carrots-watch.md         |  6 ++
 src/Playroom/Snippets/Snippets.css.ts      |  8 +-
 src/Playroom/Snippets/Snippets.tsx         | 87 +++++++---------------
 src/Playroom/Snippets/useScrollIntoView.ts | 37 +++++++++
 4 files changed, 74 insertions(+), 64 deletions(-)
 create mode 100644 .changeset/wicked-carrots-watch.md
 create mode 100644 src/Playroom/Snippets/useScrollIntoView.ts

diff --git a/.changeset/wicked-carrots-watch.md b/.changeset/wicked-carrots-watch.md
new file mode 100644
index 00000000..cb34342b
--- /dev/null
+++ b/.changeset/wicked-carrots-watch.md
@@ -0,0 +1,6 @@
+---
+'playroom': patch
+---
+
+Update snippets behaviour to instantly navigate and scroll to the currently selected snippet.
+This eliminates sluggish feeling caused by smooth scroll.
diff --git a/src/Playroom/Snippets/Snippets.css.ts b/src/Playroom/Snippets/Snippets.css.ts
index 51b49886..1b6b13ec 100644
--- a/src/Playroom/Snippets/Snippets.css.ts
+++ b/src/Playroom/Snippets/Snippets.css.ts
@@ -33,19 +33,24 @@ export const snippetsContainer = style([
     right: 0,
     overflow: 'auto',
     padding: 'none',
-    margin: 'small',
+    margin: 'none',
   }),
   {
     top: toolbarItemSize,
   },
 ]);
 
+export const snippetPadding = sprinkles({
+  padding: 'small',
+});
+
 export const snippet = style([
   sprinkles({
     position: 'relative',
     cursor: 'pointer',
     paddingY: 'large',
     paddingX: 'xlarge',
+    margin: 'none',
   }),
   {
     color: colorPaletteVars.foreground.neutral,
@@ -60,7 +65,6 @@ export const snippet = style([
       backgroundColor: colorPaletteVars.background.selection,
       borderRadius: vars.radii.medium,
       opacity: 0,
-      transition: vars.transition.slow,
       pointerEvents: 'none',
     },
   },
diff --git a/src/Playroom/Snippets/Snippets.tsx b/src/Playroom/Snippets/Snippets.tsx
index 348ed793..424a94a2 100644
--- a/src/Playroom/Snippets/Snippets.tsx
+++ b/src/Playroom/Snippets/Snippets.tsx
@@ -9,6 +9,7 @@ import { Strong } from '../Strong/Strong';
 import { Text } from '../Text/Text';
 
 import * as styles from './Snippets.css';
+import { useScrollIntoView } from './useScrollIntoView';
 
 type HighlightIndex = number | null;
 type ReturnedSnippet = Snippet | null;
@@ -29,52 +30,6 @@ const filterSnippetsForTerm = (snippets: Props['snippets'], term: string) =>
         .map(({ original, score }) => ({ ...original, score }))
     : snippets;
 
-const scrollToHighlightedSnippet = (
-  listEl: HTMLUListElement | null,
-  highlightedEl: HTMLLIElement | null
-) => {
-  if (highlightedEl && listEl) {
-    const scrollStep = Math.max(
-      Math.ceil(listEl.offsetHeight * 0.25),
-      highlightedEl.offsetHeight * 2
-    );
-    const currentListTop = listEl.scrollTop + scrollStep;
-    const currentListBottom =
-      listEl.offsetHeight + listEl.scrollTop - scrollStep;
-    let top = 0;
-
-    if (
-      highlightedEl === listEl.firstChild ||
-      highlightedEl === listEl.lastChild
-    ) {
-      highlightedEl.scrollIntoView(false);
-      return;
-    }
-
-    if (highlightedEl.offsetTop >= currentListBottom) {
-      top =
-        highlightedEl.offsetTop -
-        listEl.offsetHeight +
-        highlightedEl.offsetHeight +
-        scrollStep;
-    } else if (highlightedEl.offsetTop <= currentListTop) {
-      top = highlightedEl.offsetTop - scrollStep;
-    } else {
-      return;
-    }
-
-    if ('scrollBehavior' in window.document.documentElement.style) {
-      listEl.scrollTo({
-        left: 0,
-        top,
-        behavior: 'smooth',
-      });
-    } else {
-      listEl.scrollTo(0, top);
-    }
-  }
-};
-
 export default ({ snippets, onHighlight, onClose }: Props) => {
   const [searchTerm, setSearchTerm] = useState<string>('');
   const [highlightedIndex, setHighlightedIndex] =
@@ -94,15 +49,21 @@ export default ({ snippets, onHighlight, onClose }: Props) => {
     },
     50
   );
-  const debounceScrollToHighlighted = useDebouncedCallback(
-    scrollToHighlightedSnippet,
-    50
-  );
+
   const filteredSnippets = useMemo(
     () => filterSnippetsForTerm(snippets, searchTerm),
     [searchTerm, snippets]
   );
 
+  const highlightedItem =
+    typeof highlightedIndex === 'number'
+      ? document.getElementById(
+          `${filteredSnippets[highlightedIndex].group}_${filteredSnippets[highlightedIndex].name}_${highlightedIndex}`
+        )
+      : null;
+
+  useScrollIntoView(highlightedItem, listEl.current);
+
   useEffect(() => {
     debouncedPreview(
       typeof highlightedIndex === 'number'
@@ -125,9 +86,6 @@ export default ({ snippets, onHighlight, onClose }: Props) => {
           onBlur={() => {
             setHighlightedIndex(null);
           }}
-          onKeyUp={() => {
-            debounceScrollToHighlighted(listEl.current, highlightedEl.current);
-          }}
           onKeyDown={(event) => {
             if (/^(?:Arrow)?Down$/.test(event.key)) {
               if (
@@ -173,22 +131,27 @@ export default ({ snippets, onHighlight, onClose }: Props) => {
           return (
             <li
               ref={isHighlighted ? highlightedEl : undefined}
+              id={`${snippet.group}_${snippet.name}_${index}`}
               key={`${snippet.group}_${snippet.name}_${index}`}
-              className={classnames(styles.snippet, {
-                [styles.highlight]: isHighlighted,
-              })}
+              className={styles.snippetPadding}
               onMouseMove={
                 isHighlighted ? undefined : () => setHighlightedIndex(index)
               }
               onMouseDown={() => closeHandler(filteredSnippets[index])}
               title={getLabel(snippet)}
             >
-              <span style={{ display: 'block', position: 'relative' }}>
-                <Text size="large">
-                  <Strong>{snippet.group}</Strong>
-                  <span className={styles.snippetName}>{snippet.name}</span>
-                </Text>
-              </span>
+              <div
+                className={classnames(styles.snippet, {
+                  [styles.highlight]: isHighlighted,
+                })}
+              >
+                <span style={{ display: 'block', position: 'relative' }}>
+                  <Text size="large">
+                    <Strong>{snippet.group}</Strong>
+                    <span className={styles.snippetName}>{snippet.name}</span>
+                  </Text>
+                </span>
+              </div>
             </li>
           );
         })}
diff --git a/src/Playroom/Snippets/useScrollIntoView.ts b/src/Playroom/Snippets/useScrollIntoView.ts
new file mode 100644
index 00000000..40e5d03e
--- /dev/null
+++ b/src/Playroom/Snippets/useScrollIntoView.ts
@@ -0,0 +1,37 @@
+import { useEffect } from 'react';
+
+export function useScrollIntoView(
+  element: HTMLElement | null,
+  scrollContainer: HTMLElement | null
+) {
+  useEffect(() => {
+    if (!scrollContainer || !element) {
+      return;
+    }
+
+    const itemOffsetRelativeToContainer =
+      element.offsetParent === scrollContainer
+        ? element.offsetTop
+        : element.offsetTop - scrollContainer.offsetTop;
+
+    let { scrollTop } = scrollContainer; // Top of the visible area
+
+    if (itemOffsetRelativeToContainer < scrollTop) {
+      // Item is off the top of the visible area
+      scrollTop = itemOffsetRelativeToContainer;
+    } else if (
+      itemOffsetRelativeToContainer + element.offsetHeight >
+      scrollTop + scrollContainer.offsetHeight
+    ) {
+      // Item is off the bottom of the visible area
+      scrollTop =
+        itemOffsetRelativeToContainer +
+        element.offsetHeight -
+        scrollContainer.offsetHeight;
+    }
+
+    if (scrollTop !== scrollContainer.scrollTop) {
+      scrollContainer.scrollTop = scrollTop;
+    }
+  }, [scrollContainer, element]);
+}