fix: idle canvas animation, position overflow, title parsing

Canvas / viz:
- Idle animation when Winamp stopped/paused: slow sine-wave breathing
  across bars at low amplitude, dim colours — canvas is never dead-black
- 'PLAY' label overlay when stopped, 'NO SIGNAL' when WS disconnected
- hasSignal check: viz data must be < 1.5s old AND Winamp playing
- DPR resize uses Math.round() to avoid sub-pixel canvas size mismatch
- Peak indicators fade quickly in idle mode

winamp.go:
- GetPosition: clamp 0xFFFFFFFF sentinel at source (> 0xF0000000 → 0)
  instead of in server.go; also removed redundant clamp from statusMsg
- GetTitle: use strings.LastIndex/Index instead of hand-rolled helpers
  Returns empty string when window title is just 'Winamp' (stopped/empty)
  Playlist prefix strip is now bounded (dot <= 4) so track titles with
  '. ' in them are not accidentally trimmed

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/winamp/winamp.go

@@ -7,6 +7,7 @@ package winamp
 
 import (
 	"fmt"
+	"strings"
 	"syscall"
 	"unsafe"
 )
@@ -109,9 +110,10 @@ func (c *Controller) IsPaused() bool  { return c.PlayState() == 3 }
 func (c *Controller) IsStopped() bool { return c.PlayState() == 0 }
 
 // GetPosition returns current playback offset in seconds.
+// Returns 0 when stopped (Winamp returns 0xFFFFFFFF in that state).
 func (c *Controller) GetPosition() int {
 	v, ok := c.user(0, userGetPosition)
-	if !ok {
+	if !ok || v > 0xF0000000 { // 0xFFFFFFFF = stopped/no track
 		return 0
 	}
 	return int(v) / 1000
@@ -184,7 +186,14 @@ func (c *Controller) GetVersion() string {
 }
 
 // GetTitle returns the title of the currently playing track by reading
-// the Winamp window title (format: "N. Artist - Track - Winamp").
+// the Winamp window title.
+//
+// Winamp 5.x formats the window title as one of:
+//
+//	"N. Artist - Title - Winamp"   (playing)
+//	"Winamp"                        (stopped, no playlist)
+//
+// We strip the " - Winamp" suffix and the leading "N. " playlist prefix.
 func (c *Controller) GetTitle() string {
 	h := c.handle()
 	if h == 0 {
@@ -194,33 +203,20 @@ func (c *Controller) GetTitle() string {
 	getWindowTextW.Call(uintptr(h), uintptr(unsafe.Pointer(&buf[0])), 512)
 	title := syscall.UTF16ToString(buf)
 
-	// Strip trailing " - Winamp" suffix
+	// Strip " - Winamp" suffix (use last occurrence so track titles
+	// containing " - Winamp" are handled correctly).
 	const suffix = " - Winamp"
-	if idx := lastIndex(title, suffix); idx >= 0 {
+	if idx := strings.LastIndex(title, suffix); idx >= 0 {
 		title = title[:idx]
+	} else {
+		// Title is just "Winamp" (stopped, empty playlist).
+		return ""
 	}
-	// Strip leading playlist-number prefix "NNN. "
-	if idx := indexOf(title, ". "); idx >= 0 {
-		title = title[idx+2:]
-	}
-	return title
-}
-
-func lastIndex(s, sub string) int {
-	last := -1
-	for i := 0; i <= len(s)-len(sub); i++ {
-		if s[i:i+len(sub)] == sub {
-			last = i
-		}
-	}
-	return last
-}
 
-func indexOf(s, sub string) int {
-	for i := 0; i <= len(s)-len(sub); i++ {
-		if s[i:i+len(sub)] == sub {
-			return i
-		}
+	// Strip leading playlist-number prefix: digits followed by ". "
+	// e.g. "4. " or "12. "
+	if dot := strings.Index(title, ". "); dot >= 0 && dot <= 4 {
+		title = title[dot+2:]
 	}
-	return -1
+	return title
 }

web/static/app.js

@@ -25,10 +25,12 @@ let ws = null;
 let reconnectTimer = null;
 
 // Viz state
-const NUM_BARS = 64;
-const peaks    = new Float32Array(NUM_BARS);
-let   lastBars = new Float32Array(NUM_BARS);
-let   rafId    = null;
+const NUM_BARS  = 64;
+const peaks     = new Float32Array(NUM_BARS);
+let   lastBars  = new Float32Array(NUM_BARS);
+let   rafId     = null;
+let   lastVizAt = 0;       // timestamp of last received viz frame
+let   winampPlaying = false;
 
 // ── WebSocket ─────────────────────────────────────────────────────────────────
 function connect() {
@@ -94,6 +96,7 @@ function applyStatus(st) {
   }
 
   btnPlay.textContent = st.state === 'playing' ? '⏸' : '▶';
+  winampPlaying = st.state === 'playing';
 
   if (typeof st.volume === 'number') {
     currentVolume = st.volume;
@@ -193,54 +196,88 @@ $('btn-close-killist').addEventListener('click', () =>
 function applyViz(bars) {
   if (!bars || bars.length === 0) return;
   lastBars = new Float32Array(bars);
+  lastVizAt = performance.now();
 }
 
-function renderFrame() {
+function renderFrame(ts = 0) {
   rafId = requestAnimationFrame(renderFrame);
 
-  // Resize canvas to CSS size (handles window resize / DPR)
-  const dpr = window.devicePixelRatio || 1;
+  // Resize canvas to CSS size (handles window resize / DPR).
+  // Setting canvas.width resets the transform, so we re-apply scale.
+  const dpr  = window.devicePixelRatio || 1;
   const cssW = canvas.clientWidth;
   const cssH = canvas.clientHeight;
-  if (canvas.width !== cssW * dpr || canvas.height !== cssH * dpr) {
-    canvas.width  = cssW * dpr;
-    canvas.height = cssH * dpr;
+  if (canvas.width !== Math.round(cssW * dpr) || canvas.height !== Math.round(cssH * dpr)) {
+    canvas.width  = Math.round(cssW * dpr);
+    canvas.height = Math.round(cssH * dpr);
     ctx2d.scale(dpr, dpr);
   }
 
   const w = cssW;
   const h = cssH;
-  const n = lastBars.length || NUM_BARS;
+  if (w === 0 || h === 0) return;
+
+  // Check if real viz data is fresh (< 1.5 s old) and Winamp is playing.
+  const hasSignal = winampPlaying && (performance.now() - lastVizAt) < 1500;
 
   // Background
   ctx2d.fillStyle = '#000';
   ctx2d.fillRect(0, 0, w, h);
 
+  const n    = NUM_BARS;
   const gap  = 1;
-  const barW = (w - gap * (n - 1)) / n;
+  const barW = Math.max(1, (w - gap * (n - 1)) / n);
 
   for (let i = 0; i < n; i++) {
-    const val = lastBars[i] || 0;
-
-    // Peak: fast rise, slow fall (2% per frame)
-    if (val > peaks[i]) peaks[i] = val;
-    else peaks[i] = Math.max(0, peaks[i] - 0.012);
+    let val;
+
+    if (hasSignal) {
+      // Real spectrum data
+      val = lastBars[i] || 0;
+      if (val > peaks[i]) peaks[i] = val;
+      else peaks[i] = Math.max(0, peaks[i] - 0.012);
+    } else {
+      // Idle animation: slow sine "breathing" across the bars.
+      // Amplitude fades out when paused/stopped.
+      const phase  = (ts / 1800) + (i / n) * Math.PI * 2;
+      const breath = (Math.sin(ts / 2000) * 0.5 + 0.5) * 0.08; // 0..0.08
+      val = Math.max(0, Math.sin(phase) * breath);
+      peaks[i] = Math.max(0, peaks[i] - 0.02); // let peaks fall quickly
+    }
 
-    const x    = i * (barW + gap);
+    const x    = Math.round(i * (barW + gap));
     const barH = val * h;
 
-    // Bar colour: green (120°) → yellow (60°) → red (0°) based on amplitude
-    const hue = Math.round((1 - val) * 120);
-    ctx2d.fillStyle = `hsl(${hue},100%,42%)`;
-    ctx2d.fillRect(x, h - barH, barW, barH);
+    if (barH > 0.5) {
+      // Bar colour: green (120°) → yellow (60°) → red (0°)
+      const hue = Math.round((1 - val) * 120);
+      const lit  = hasSignal ? 42 : 25; // dimmer in idle
+      ctx2d.fillStyle = `hsl(${hue},100%,${lit}%)`;
+      ctx2d.fillRect(x, h - barH, barW, barH);
+    }
 
-    // Peak indicator — thin white line
+    // Peak indicator
     if (peaks[i] > 0.02) {
-      const py = h - peaks[i] * h - 1;
-      ctx2d.fillStyle = 'rgba(255,255,255,0.75)';
+      const py = Math.round(h - peaks[i] * h) - 1;
+      ctx2d.fillStyle = hasSignal ? 'rgba(255,255,255,0.75)' : 'rgba(255,255,255,0.2)';
       ctx2d.fillRect(x, py, barW, 2);
     }
   }
+
+  // "No signal" label when disconnected or stopped
+  if (!ws || ws.readyState !== WebSocket.OPEN) {
+    drawLabel(ctx2d, w, h, '● NO SIGNAL', '#333');
+  } else if (!winampPlaying) {
+    drawLabel(ctx2d, w, h, '▶ PLAY', '#1a3a1a');
+  }
+}
+
+function drawLabel(ctx, w, h, text, color) {
+  ctx.font = `bold ${Math.round(h * 0.22)}px monospace`;
+  ctx.textAlign = 'center';
+  ctx.textBaseline = 'middle';
+  ctx.fillStyle = color;
+  ctx.fillText(text, w / 2, h / 2);
 }
 
 // ── Helpers ───────────────────────────────────────────────────────────────────