fix: keep group visible as header for the running event

apps/client/src/features/operator/Operator.module.scss

@@ -18,6 +18,12 @@
   padding-bottom: 95vh;
 }
 
+.groupSection {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
 .editPrompt {
   position: fixed;
   z-index: $zindex-dialog;

apps/client/src/features/operator/Operator.tsx

@@ -1,5 +1,5 @@
 import { OntimeView, isOntimeEvent, isOntimeGroup } from 'ontime-types';
-import { Fragment, useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 
 import EmptyFill from '../../common/components/state/EmptyFill';
 import EmptyPage from '../../common/components/state/EmptyPage';
@@ -25,7 +25,10 @@ import { OperatorData, useOperatorData } from './useOperatorData';
 
 import style from './Operator.module.scss';
 
-const selectedOffset = 50;
+/** Keeps the running event clear of the list edge when no group header is pinned above it */
+const edgeOffset = 50;
+/** How far the running event may drift from where we placed it before we stop following */
+const followTolerance = 50;
 
 export default function OperatorLoader() {
   const { data, status } = useOperatorData();
@@ -54,11 +57,20 @@ function Operator({ rundown, rundownMetadata, customFields, settings }: Operator
   const [lockAutoScroll, setLockAutoScroll] = useState(false);
   const selectedRef = useRef<HTMLDivElement | null>(null);
   const scrollRef = useRef<HTMLDivElement | null>(null);
+  const stickyHeaderRef = useRef<HTMLDivElement | null>(null);
+
+  // The header height varies with the viewport, so measure it at scroll time.
+  const getTopOffset = useCallback(() => {
+    const header = stickyHeaderRef.current;
+    // Sit right under the pinned header, so it covers the previous event instead of half of it.
+    return header ? header.offsetHeight + 2 : edgeOffset;
+  }, []);
+
   const scrollToComponent = useFollowComponent({
     followRef: selectedRef,
     scrollRef,
     doFollow: !lockAutoScroll,
-    topOffset: selectedOffset,
+    getTopOffset,
     followTrigger: selectedEventId,
   });
 
@@ -82,15 +94,16 @@ function Operator({ rundown, rundownMetadata, customFields, settings }: Operator
 
   // prevent considering automated scrolls as user scrolls
   const handleUserScroll = () => {
-    if (selectedRef?.current && scrollRef?.current) {
-      const selectedRect = selectedRef.current.getBoundingClientRect();
-      const scrollerRect = scrollRef.current.getBoundingClientRect();
-      if (selectedRect && scrollerRect) {
-        const distanceFromTop = selectedRect.top - scrollerRect.top;
-        const hasScrolledOutOfThreshold = distanceFromTop < -8 || distanceFromTop > selectedOffset;
-        setLockAutoScroll(hasScrolledOutOfThreshold);
-      }
+    if (!selectedRef.current || !scrollRef.current) {
+      return;
     }
+
+    const selectedRect = selectedRef.current.getBoundingClientRect();
+    const scrollerRect = scrollRef.current.getBoundingClientRect();
+    // Measure the drift from where an automated scroll would place the event.
+    const distanceFromTop = selectedRect.top - scrollerRect.top - getTopOffset();
+    const hasScrolledOutOfThreshold = distanceFromTop < -8 || distanceFromTop > followTolerance;
+    setLockAutoScroll(hasScrolledOutOfThreshold);
   };
   const throttledHandleScroll = throttle(handleUserScroll, 1000);
 
@@ -186,9 +199,9 @@ function Operator({ rundown, rundownMetadata, customFields, settings }: Operator
               }
 
               return (
-                <Fragment key={entry.id}>
+                <div className={style.groupSection} key={entry.id}>
                   <OperatorGroup
-                    key={entry.id}
+                    ref={isCurrentParent ? stickyHeaderRef : undefined}
                     title={entry.title}
                     colour={entry.colour}
                     count={entry.entries.length}
@@ -239,7 +252,7 @@ function Operator({ rundown, rundownMetadata, customFields, settings }: Operator
                       />
                     );
                   })}
-                </Fragment>
+                </div>
               );
             }
             return null;

apps/client/src/features/operator/operator-group/OperatorGroup.module.scss

@@ -1,13 +1,20 @@
 .group {
   width: 100%;
+  /* Padding is kept under the min-height so a single line fits without the list having to shrink the header,
+     while a taller title still grows the row. */
   min-height: 2.5rem;
-  padding: 0.4rem 0.75rem;
+  padding: 0.25rem 0.75rem;
   border-left: 0.35rem solid var(--group-colour, $gray-500);
   background-color: $gray-1350;
   background: color-mix(in srgb, transparent 88%, var(--group-colour, $gray-500) 12%);
   font-size: 1.25rem;
   font-weight: 600;
 
+  position: sticky;
+  /* Cover the list padding so rows cannot scroll above the header. */
+  top: -0.25rem;
+  z-index: 1;
+
   display: flex;
   align-items: center;
   gap: 1rem;

apps/client/src/features/operator/operator-group/OperatorGroup.tsx

@@ -1,4 +1,4 @@
-import { CSSProperties, memo } from 'react';
+import { type CSSProperties, type Ref, memo } from 'react';
 
 import { getAccessibleColour } from '../../../common/utils/styleUtils';
 import { formatDuration } from '../../../common/utils/time';
@@ -10,15 +10,16 @@ interface OperatorGroup {
   colour: string;
   count: number;
   duration: number;
+  ref?: Ref<HTMLDivElement>;
 }
 
 export default memo(OperatorGroup);
-function OperatorGroup({ title, colour, count, duration }: OperatorGroup) {
+function OperatorGroup({ title, colour, count, duration, ref }: OperatorGroup) {
   const groupColour = colour || '#929292';
   const groupColours = getAccessibleColour(groupColour);
 
   return (
-    <div className={style.group} style={{ ...groupColours, '--group-colour': groupColour } as CSSProperties}>
+    <div className={style.group} style={{ ...groupColours, '--group-colour': groupColour } as CSSProperties} ref={ref}>
       <span className={style.title}>{title}</span>
       <span className={style.meta}>
         <span>{`${count} ${count === 1 ? 'event' : 'events'}`}</span>