⚡️(frontend) reduce re-renders of the ParticipantTile focus overlay

Optimize the idle mouse handling and the FocusOverlay component so
they no longer trigger frequent re-renders of the ParticipantTile
focus.

State related to hover and focus is now scoped closer to where it
is used, keeping updates local instead of propagating up the tile.

src/frontend/panda.config.ts

@@ -114,6 +114,10 @@ const config: Config = {
           clipPath: 'polygon(50% 50%, 0 0, 100% 0, 100% 100%, 0 100%, 0 0)',
         },
       },
+      overlayIn: {
+        from: { opacity: 0 },
+        to: { opacity: 0.6 },
+      },
     },
     tokens: defineTokens({
       /* we take a few things from the panda preset but for now we clear out some stuff.

src/frontend/src/features/participantTile/components/participantTileFocus/ParticipantTileFocus.tsx

@@ -1,7 +1,7 @@
 import { css } from '@/styled-system/css'
 import { HStack } from '@/styled-system/jsx'
 import { TrackReferenceOrPlaceholder } from '@livekit/components-core'
-import { useEffect, useRef, useState } from 'react'
+import { ReactNode, useEffect, useRef, useState } from 'react'
 import { Track } from 'livekit-client'
 import { useCanMute } from '@/features/rooms/livekit/hooks/useCanMute'
 import { FocusButton } from './FocusButton'
@@ -11,49 +11,34 @@ import { ZoomButton } from './ZoomButton'
 
 const MOUSE_IDLE_TIME = 3000
 
-export const ParticipantTileFocus = ({
-  trackRef,
-  hasKeyboardFocus,
-}: {
-  trackRef: TrackReferenceOrPlaceholder
+type FadeOverlayProps = {
+  children: ReactNode
   hasKeyboardFocus: boolean
-}) => {
-  const [hovered, setHovered] = useState(false)
-  const [opacity, setOpacity] = useState(0)
+}
 
+const FadeOverlay = ({ children, hasKeyboardFocus }: FadeOverlayProps) => {
+  const [active, setActive] = useState(false)
   const idleTimerRef = useRef<number | null>(null)
-  const [isIdleRef, setIsIdleRef] = useState(false)
 
-  const isVisible = hasKeyboardFocus || (hovered && !isIdleRef)
-
-  useEffect(() => {
-    if (isVisible) {
-      // Wait for next frame to ensure element is mounted
-      requestAnimationFrame(() => {
-        setOpacity(0.6)
-      })
-    } else {
-      setOpacity(0)
-    }
-  }, [isVisible])
-
-  const handleMouseMove = () => {
-    if (idleTimerRef.current) {
-      window.clearTimeout(idleTimerRef.current)
-    }
-    idleTimerRef.current = window.setTimeout(() => {
-      setIsIdleRef(true)
-    }, MOUSE_IDLE_TIME)
-    setIsIdleRef(false)
+  const clearIdleTimer = () => {
+    if (idleTimerRef.current) window.clearTimeout(idleTimerRef.current)
   }
 
-  const participant = trackRef.participant
+  const armIdleTimer = () => {
+    clearIdleTimer()
+    idleTimerRef.current = window.setTimeout(() => {
+      setActive(false)
+    }, MOUSE_IDLE_TIME)
+  }
 
-  const isScreenShare = trackRef.source == Track.Source.ScreenShare
-  const isLocal = trackRef.participant.isLocal
+  const handleActivity = () => {
+    setActive(true)
+    armIdleTimer()
+  }
 
-  const canMute = useCanMute(participant)
+  useEffect(() => clearIdleTimer, [])
 
+  const isVisible = hasKeyboardFocus || active
   return (
     <div
       className={css({
@@ -66,49 +51,62 @@ export const ParticipantTileFocus = ({
         width: '100%',
         height: '100%',
       })}
+      data-visible={isVisible || undefined}
       aria-hidden={!isVisible}
-      onMouseEnter={() => setHovered(true)}
-      onMouseLeave={() => setHovered(false)}
-      onMouseMove={handleMouseMove}
+      onMouseEnter={handleActivity}
+      onMouseMove={handleActivity}
+      onMouseLeave={() => {
+        clearIdleTimer()
+        setActive(false)
+      }}
     >
-      {isVisible && (
-        <div
-          className={css({
-            backgroundColor: 'primaryDark.50',
-            transition: 'opacity 200ms linear',
-            zIndex: 1,
-            borderRadius: '0.25rem',
-            display: 'flex',
-            _hover: {
-              opacity: '0.95 !important',
-            },
-          })}
-          style={{ opacity }}
-        >
-          <HStack
-            gap={0.5}
-            className={css({
-              padding: '0.5rem',
-              _hover: {
-                opacity: '1 !important',
-              },
-            })}
-          >
-            <FocusButton trackRef={trackRef} />
-            {!isScreenShare ? (
-              <>
-                {participant.isLocal ? (
-                  <EffectsButton />
-                ) : (
-                  canMute && <MuteButton participant={participant} />
-                )}
-              </>
-            ) : (
-              !isLocal && <ZoomButton trackRef={trackRef} />
-            )}
-          </HStack>
-        </div>
-      )}
+      {isVisible && children}
     </div>
   )
 }
+
+export const ParticipantTileFocus = ({
+  trackRef,
+  hasKeyboardFocus,
+}: {
+  trackRef: TrackReferenceOrPlaceholder
+  hasKeyboardFocus: boolean
+}) => {
+  const participant = trackRef.participant
+  const isScreenShare = trackRef.source == Track.Source.ScreenShare
+  const isLocal = participant.isLocal
+  const canMute = useCanMute(participant)
+
+  return (
+    <FadeOverlay hasKeyboardFocus={hasKeyboardFocus}>
+      <div
+        className={css({
+          backgroundColor: 'primaryDark.50',
+          zIndex: 1,
+          borderRadius: '0.25rem',
+          display: 'flex',
+          opacity: 0.6,
+          animation: 'overlayIn 200ms linear 300ms backwards',
+          _hover: {
+            opacity: 0.95,
+          },
+        })}
+      >
+        <HStack gap={0.5} padding={0.5}>
+          <FocusButton trackRef={trackRef} />
+          {!isScreenShare ? (
+            <>
+              {isLocal ? (
+                <EffectsButton />
+              ) : (
+                canMute && <MuteButton participant={participant} />
+              )}
+            </>
+          ) : (
+            !isLocal && <ZoomButton trackRef={trackRef} />
+          )}
+        </HStack>
+      </div>
+    </FadeOverlay>
+  )
+}