feat: replace progress bar with scrollable waveform display

index.html

@@ -32,9 +32,8 @@ canvas { width: 100%; height: 100px; border-radius: 6px; display: block; }
 .big-time .sep { color: #6b7089; margin: 0 4px; }
 .canvas-area { display: flex; flex-direction: column; flex: 1; min-width: 200px; gap: 6px; }
 .progress-row { display: flex; align-items: center; gap: 8px; font-size: 11px; color: #6b7089; font-variant-numeric: tabular-nums; font-family: 'SF Mono', 'Fira Code', 'Cascadia Code', monospace; }
-.progress-row .progress-bar { flex: 1; height: 6px; background: #272c42; border-radius: 3px; cursor: pointer; }
-.progress-row .progress-bar .fill { height: 100%; background: #84a0c6; border-radius: 3px; width: 0%; }
-.progress-row .progress-bar:hover .fill { background: #91acd1; }
+.waveform-wrap { flex: 1; overflow-x: auto; overflow-y: hidden; cursor: pointer; position: relative; height: 42px; }
+.waveform-wrap canvas { display: block; height: 42px; }
 #noiz-overlay { position: fixed; opacity: 0.75; inset: 0; display: flex; justify-content: center; align-items: center; background: transparent; pointer-events: none; z-index: 9999; animation: fadeout 750ms ease 750ms forwards; }
 #noiz-overlay img { max-width: 50vw; max-height: 50vh; filter: drop-shadow(0 8px 16px rgba(0,0,0,0.5)); }
 @keyframes fadeout { from { opacity: 0.75; transform: scale(1); } to { opacity: 0; transform: scale(1.75); visibility: hidden; } }
@@ -141,8 +140,8 @@ footer .footer-track { flex: 1; min-width: 0; white-space: nowrap; overflow: hid
         <canvas id="spectrum" width="480" height="200"></canvas>
         <div class="progress-row" id="progressRow">
           <span id="timeCurrent">0:00</span>
-          <div class="progress-bar" id="progressBar">
-            <div class="fill" id="progressFill"></div>
+          <div class="waveform-wrap" id="waveformWrap">
+            <canvas id="waveform"></canvas>
           </div>
           <span id="timeRemaining">0:00</span>
         </div>
@@ -571,6 +570,91 @@ function drawSpectrum() {
   animId = requestAnimationFrame(drawSpectrum);
 }
 drawSpectrum();
+const WF_PPS = 6;
+const WF_HEIGHT = 42;
+function computeWaveform(t) {
+  if (t.waveform || !t.file) return;
+  fetch(t.url)
+    .then(r => r.arrayBuffer())
+    .then(buf => {
+      if (!audioCtx) initAudioCtx();
+      return audioCtx.decodeAudioData(buf);
+    })
+    .then(ab => {
+      const ch = ab.getChannelData(0);
+      const len = Math.ceil(t.playtime * WF_PPS);
+      const step = Math.max(1, Math.floor(ch.length / len));
+      const data = new Float32Array(len * 2);
+      for (let i = 0; i < len; i++) {
+        let mn = 0, mx = 0;
+        const start = i * step;
+        const end = Math.min(start + step, ch.length);
+        for (let j = start; j < end; j++) {
+          if (ch[j] < mn) mn = ch[j];
+          if (ch[j] > mx) mx = ch[j];
+        }
+        data[i * 2] = mn;
+        data[i * 2 + 1] = mx;
+      }
+      t.waveform = { len, data };
+      drawWaveform();
+    })
+    .catch(() => {});
+}
+function drawWaveform() {
+  const t = tracks[currentIndex];
+  const dpr = window.devicePixelRatio || 1;
+  const wrap = waveformWrap;
+  const visWidth = wrap.clientWidth;
+  const canvas = waveformCanvas;
+  const h = WF_HEIGHT;
+  canvas.style.height = h + 'px';
+  if (!t || !t.waveform) {
+    canvas.style.width = visWidth + 'px';
+    canvas.width = Math.round(visWidth * dpr);
+    canvas.height = Math.round(h * dpr);
+    const ctx = canvas.getContext('2d');
+    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
+    ctx.clearRect(0, 0, visWidth, h);
+    return;
+  }
+  const wf = t.waveform;
+  const totalWidth = wf.len;
+  const newWidth = Math.max(totalWidth, visWidth);
+  canvas.style.width = newWidth + 'px';
+  canvas.style.height = h + 'px';
+  canvas.width = Math.round(newWidth * dpr);
+  canvas.height = Math.round(h * dpr);
+  const ctx = canvas.getContext('2d');
+  ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
+  ctx.clearRect(0, 0, newWidth, h);
+  const halfH = h / 2;
+  const ampScale = halfH * 0.85;
+  let playheadX = -1;
+  if (audio && audio.duration && t.playtime) {
+    const pct = audio.currentTime / audio.duration;
+    playheadX = pct * totalWidth;
+  }
+  const data = wf.data;
+  for (let i = 0; i < wf.len; i++) {
+    const mn = data[i * 2];
+    const mx = data[i * 2 + 1];
+    const y1 = halfH + mn * ampScale;
+    const y2 = halfH + mx * ampScale;
+    ctx.fillStyle = playheadX >= 0 && i < playheadX ? '#6b88b0' : '#84a0c6';
+    ctx.fillRect(i, y1, 1, Math.max(1, y2 - y1));
+  }
+  if (playheadX >= 0) {
+    ctx.strokeStyle = '#e27878';
+    ctx.lineWidth = 1;
+    ctx.beginPath();
+    ctx.moveTo(playheadX, 2);
+    ctx.lineTo(playheadX, h - 2);
+    ctx.stroke();
+    const targetScroll = playheadX - visWidth / 2;
+    wrap.scrollLeft = Math.max(0, Math.min(targetScroll, totalWidth - visWidth));
+  }
+}
 let tracks = [];
 let currentIndex = -1;
 let selectedIndices = new Set();
@@ -597,8 +681,8 @@ const trackArtist = document.getElementById('trackArtist');
 const playBtn = document.getElementById('playBtn');
 const prevBtn = document.getElementById('prevBtn');
 const nextBtn = document.getElementById('nextBtn');
-const progressFill = document.getElementById('progressFill');
-const progressBar = document.getElementById('progressBar');
+const waveformCanvas = document.getElementById('waveform');
+const waveformWrap = document.getElementById('waveformWrap');
 const timeCurrent = document.getElementById('timeCurrent');
 const timeRemaining = document.getElementById('timeRemaining');
 const progressRow = document.getElementById('progressRow');
@@ -1313,6 +1397,7 @@ function playTrack(i) {
         }, cd * 1000 + 100);
         updateUI();
         renderTracks();
+        drawWaveform();
       };
     audioNext.addEventListener('canplaythrough', onReady);
   } else {
@@ -1324,6 +1409,7 @@ function playTrack(i) {
     initAudioCtx();
     updateUI();
     renderTracks();
+    drawWaveform();
   }
 }
 function updateUI() {
@@ -1349,14 +1435,14 @@ function onLoadedmetadata(e) {
   if (t && audio.duration) {
     t.playtime = audio.duration;
     renderTracks();
+    computeWaveform(t);
   }
 }
 function onTimeupdate(e) {
   if (e.target !== audio) return;
   if (!audio.duration) return;
-  const pct = (audio.currentTime / audio.duration) * 100;
   const remaining = audio.duration - audio.currentTime;
-  progressFill.style.width = pct + '%';
+  drawWaveform();
   timeCurrent.textContent = fmtTime(audio.currentTime);
   timeRemaining.textContent = '-' + fmtTime(remaining);
   bigTime.innerHTML = `${fmtTime(audio.currentTime)} <span class="sep">/</span> ${fmtTime(audio.duration)}`;
@@ -1448,10 +1534,15 @@ function nextTrack() {
     playTrack(currentIndex >= tracks.length - 1 ? 0 : currentIndex + 1);
   }
 }
-progressBar.addEventListener('click', (e) => {
+waveformWrap.addEventListener('click', (e) => {
   if (!audio.duration) return;
-  const rect = progressBar.getBoundingClientRect();
-  audio.currentTime = ((e.clientX - rect.left) / rect.width) * audio.duration;
+  if (e.target !== waveformCanvas) return;
+  const t = tracks[currentIndex];
+  if (!t || !t.waveform) return;
+  const rect = waveformCanvas.getBoundingClientRect();
+  const x = e.clientX - rect.left + waveformWrap.scrollLeft;
+  const pct = x / t.waveform.length;
+  audio.currentTime = pct * audio.duration;
 });
 volumeSlider.addEventListener('input', () => {
   const v = parseFloat(volumeSlider.value);