Add real-time CAVA audio visualizer for VU bars

CAVA runs in background via cava-start.sh, writing bar values to
/tmp/skeledance_bars. A new QML DataSource polls that file at 80ms
and calls updateBars() in JS. Falls back to rest state when not playing.

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

plugin/contents/ui/cava-start.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# Kill any previous instance tied to this config
+pkill -f "cava -p.*skeledance" 2>/dev/null
+sleep 0.2
+
+CONF="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/cava.conf"
+cava -p "$CONF" | while IFS= read -r line; do
+    printf '%s\n' "$line" > /tmp/skeledance_bars
+done

plugin/contents/ui/cava.conf

@@ -0,0 +1,14 @@
+[general]
+bars = 38
+framerate = 60
+sleep_timer = 0
+
+[input]
+method = pulse
+
+[output]
+method = raw
+raw_target = /dev/stdout
+data_format = ascii
+ascii_max_range = 100
+bar_delimiter = 59

plugin/contents/ui/dancer.html

@@ -873,33 +873,30 @@ const VU_PALETTE = [
   '#00eebb','#00ddaa','#00cc99','#00bb88',
 ];
 
+const MAX_BAR_H = 70;
+
 for (let i = 0; i < VU_COUNT; i++) {
   const bar      = document.createElement('div');
   bar.className  = 'vu-bar';
   bar.style.background = VU_PALETTE[i % VU_PALETTE.length];
   bar.style.boxShadow  = `0 0 4px ${VU_PALETTE[i % VU_PALETTE.length]}`;
-  bar._maxH  = 15 + Math.random() * 55;
-  bar._phase = Math.random() * Math.PI * 2;
-  bar._speed = 1.5 + Math.random() * 4;
+  bar.style.height     = '3px';
+  bar.style.opacity    = '0.15';
   vuMeter.appendChild(bar);
   vuBars.push(bar);
 }
 
-function animateVU(ts) {
-  const t = ts * 0.001;
-  vuBars.forEach(bar => {
-    if (isPlaying) {
-      const h = bar._maxH * Math.abs(Math.sin(t * bar._speed + bar._phase));
-      bar.style.height  = Math.max(3, h) + 'px';
-      bar.style.opacity = 0.55 + 0.45 * (h / bar._maxH);
-    } else {
-      bar.style.height  = '3px';
-      bar.style.opacity = '0.15';
-    }
+// Called by QML with semicolon-separated CAVA values (0–100 per bar)
+function updateBars(raw) {
+  if (!isPlaying) return;
+  const vals = raw.split(';');
+  vuBars.forEach((bar, i) => {
+    const v   = Math.min(100, parseInt(vals[i] || 0, 10));
+    const h   = Math.max(3, (v / 100) * MAX_BAR_H);
+    bar.style.height  = h + 'px';
+    bar.style.opacity = 0.3 + 0.7 * (v / 100);
   });
-  requestAnimationFrame(animateVU);
 }
-requestAnimationFrame(animateVU);
 
 /* ============================================================
    FLOATING MUSIC NOTES
@@ -943,8 +940,9 @@ function updateMusic(artist, title) {
              : (title || artist || '— —');
   const playing = !!(artist || title);
   isPlaying = playing;
-  document.querySelector('.robot-wrap').style.opacity  = playing ? '1' : '0';
+  document.querySelector('.robot-wrap').style.opacity   = playing ? '1' : '0';
   document.querySelector('.music-ticker').style.opacity = playing ? '1' : '0';
+  if (!playing) vuBars.forEach(b => { b.style.height = '3px'; b.style.opacity = '0.15'; });
   if (el.textContent === text) return;
   el.textContent = text;
   if (playing) pickSkeleton();

plugin/contents/ui/main.qml

@@ -24,6 +24,14 @@ WallpaperItem {
         }
     }
 
+    // Start CAVA on load
+    Plasma5Support.DataSource {
+        id: cavaStarter
+        engine: "executable"
+        connectedSources: ["bash " + Qt.resolvedUrl("cava-start.sh").toString().replace("file://", "") + " &"]
+        interval: 0
+    }
+
     // Polls playerctl every 2s and injects music info into the page
     Plasma5Support.DataSource {
         id: musicSource
@@ -42,4 +50,19 @@ WallpaperItem {
             )
         }
     }
+
+    // Polls CAVA bars at ~60fps
+    Plasma5Support.DataSource {
+        id: cavaSource
+        engine: "executable"
+        connectedSources: ["cat /tmp/skeledance_bars 2>/dev/null || echo ''"]
+        interval: 80
+
+        onNewData: function(sourceName, data) {
+            var raw = data["stdout"].trim()
+            if (raw !== "") {
+                webView.runJavaScript("updateBars(" + JSON.stringify(raw) + ")")
+            }
+        }
+    }
 }