From 6c502749501524acfaa307be17adf521dc3f52c8 Mon Sep 17 00:00:00 2001
From: Brent Vollebregt <brent.vollebregt@gmail.com>
Date: Mon, 22 Jan 2024 17:06:40 +1300
Subject: [PATCH] Use smoothing delay to calculate lyric position rather than
 API requests

---
 client/src/components/Player.tsx              |  2 +-
 client/src/hooks/useSmoothProgress.ts         |  4 +--
 client/src/pages/LyricsView/LyricsDisplay.tsx | 28 +++++++++++--------
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/client/src/components/Player.tsx b/client/src/components/Player.tsx
index ac60772..27f2570 100644
--- a/client/src/components/Player.tsx
+++ b/client/src/components/Player.tsx
@@ -118,7 +118,7 @@ const Player: React.FC<PlayerProps> = ({ currentlyPlayingSong, token }) => {
           </div>
 
           <Box display="inline-flex" alignItems="center" className={classes.sliderWrapper}>
-            <span className={classes.timeControl}>{formatMilliseconds(progressMs)}</span>
+            <span className={classes.timeControl}>{formatMilliseconds(smoothedProgressMs)}</span>
 
             <Slider
               valueLabelDisplay="off"
diff --git a/client/src/hooks/useSmoothProgress.ts b/client/src/hooks/useSmoothProgress.ts
index 5f59df6..a96e28f 100644
--- a/client/src/hooks/useSmoothProgress.ts
+++ b/client/src/hooks/useSmoothProgress.ts
@@ -7,7 +7,8 @@ const useSmoothProgress = (
   progressMs: number,
   duration: number,
   isPlaying: boolean,
-  token: IToken | null
+  token: IToken | null,
+  smoothingDelay: number = 500
 ) => {
   const [progress, setProgress] = useState(0);
   const [userSlidingProgress, setUserSlidingProgress] = useState(false);
@@ -26,7 +27,6 @@ const useSmoothProgress = (
       clearTimeout(smoothProgressTimer);
     }
 
-    const smoothingDelay = 500;
     setSmoothProgressTimer(
       setInterval(() => {
         if (!userSlidingProgress && isPlaying) {
diff --git a/client/src/pages/LyricsView/LyricsDisplay.tsx b/client/src/pages/LyricsView/LyricsDisplay.tsx
index 82dc3dc..71308eb 100644
--- a/client/src/pages/LyricsView/LyricsDisplay.tsx
+++ b/client/src/pages/LyricsView/LyricsDisplay.tsx
@@ -13,13 +13,11 @@ import SearchIcon from "@material-ui/icons/Search";
 import SyncEnabledIcon from "@material-ui/icons/Sync";
 import SyncDisabledIcon from "@material-ui/icons/SyncDisabled";
 import MarkJS from "mark.js";
-import React, { useEffect, useRef, useState } from "react";
+import React, { useEffect, useMemo, useRef, useState } from "react";
 import { IFoundLyrics } from "../../../../src/dto";
+import useSmoothProgress from "../../hooks/useSmoothProgress";
 import "./LyricsDisplay.css";
 
-// adjusting for latency to highlight lyrics due to the time it takes to render the components on screen
-const LATENCY_ADJUSTMENT_MAGIC_VALUE_MS = 0.135;
-
 interface IProps {
   lyricsDetails: IFoundLyrics;
   progressMs: number;
@@ -35,6 +33,14 @@ const LyricsDisplay: React.FunctionComponent<IProps> = ({ lyricsDetails, progres
   const [searchShown, setSearchShown] = useState(false);
   const [syncEnabled, setSyncEnabled] = useState(true);
 
+  const { progress: smoothedProgressMs } = useSmoothProgress(
+    progressMs,
+    Infinity,
+    !paused,
+    null,
+    250
+  );
+
   const isSyncingPossible = lyricsDetails.syncedLyrics !== null;
 
   // Highlight text when the search is changed
@@ -61,9 +67,12 @@ const LyricsDisplay: React.FunctionComponent<IProps> = ({ lyricsDetails, progres
     if (syncEnabled && element !== null) {
       element.scrollIntoView({ behavior: "smooth", block: "center", inline: "nearest" });
     }
-  }, [syncEnabled, progressMs]);
+  }, [syncEnabled, smoothedProgressMs]);
 
-  const lyricsState = calculateLyricsState(lyricsDetails, progressMs, syncEnabled, paused);
+  const lyricsState = useMemo(
+    () => calculateLyricsState(lyricsDetails, smoothedProgressMs, syncEnabled, paused),
+    [lyricsDetails, smoothedProgressMs, syncEnabled, paused]
+  );
 
   const onUserSearch = (event: React.ChangeEvent<HTMLTextAreaElement | HTMLInputElement>) =>
     setSearch(event.currentTarget.value ?? "");
@@ -135,7 +144,6 @@ const calculateLyricsState = (
   paused: boolean
 ) => {
   const progressSeconds = progressMs / 1000;
-  const artificialProgressSeconds = progressSeconds + LATENCY_ADJUSTMENT_MAGIC_VALUE_MS / 1000;
 
   // If there is no syncedLyricsArray or sync is disabled or the song is paused, return the plain lyrics
   if (lyricsDetails.syncedLyrics === null || !syncEnabled || paused) {
@@ -148,15 +156,13 @@ const calculateLyricsState = (
 
   // Calculate the current lyric state based on progress
   const passedLyricsAndCurrent =
-    lyricsDetails.syncedLyrics.filter(x => x.timestamp <= artificialProgressSeconds) ?? [];
+    lyricsDetails.syncedLyrics.filter(x => x.timestamp <= progressSeconds) ?? [];
   const passedLyrics = passedLyricsAndCurrent.slice(0, -1);
   const currentLyrics =
     passedLyricsAndCurrent.length > 0
       ? passedLyricsAndCurrent[passedLyricsAndCurrent.length - 1]
       : null;
-  const upcomingLyrics = lyricsDetails.syncedLyrics.filter(
-    x => x.timestamp > artificialProgressSeconds
-  );
+  const upcomingLyrics = lyricsDetails.syncedLyrics.filter(x => x.timestamp > progressSeconds);
 
   return {
     before: passedLyrics.map(x => x.content).join(" \n "),