refactor: Migrate screen sharing media handling from direct WebRTC to Mediasoup.

client/pipewire.js

@@ -254,6 +254,55 @@ class PipewireHelper {
             return false;
         }
     }
+    // Monitor PipeWire graph for changes (new/removed audio streams)
+    // Calls `onChange` whenever a relevant change is detected (debounced)
+    static _monitorProcess = null;
+    static _debounceTimer = null;
+
+    static startMonitoring(onChange) {
+        if (this._monitorProcess) return; // already monitoring
+
+        const { spawn } = require('child_process');
+        // pw-mon outputs a line for every PipeWire graph event (node added, removed, etc.)
+        const proc = spawn('pw-mon', ['--color=never'], {
+            stdio: ['ignore', 'pipe', 'ignore']
+        });
+
+        this._monitorProcess = proc;
+
+        proc.stdout.on('data', (data) => {
+            const text = data.toString();
+            // Only react to node add/remove events that are likely audio-related
+            if (text.includes('added') || text.includes('removed')) {
+                // Debounce: multiple events fire in quick succession when an app starts/stops
+                clearTimeout(this._debounceTimer);
+                this._debounceTimer = setTimeout(() => {
+                    onChange();
+                }, 500);
+            }
+        });
+
+        proc.on('error', (err) => {
+            console.error('pw-mon failed to start:', err.message);
+            this._monitorProcess = null;
+        });
+
+        proc.on('exit', () => {
+            this._monitorProcess = null;
+        });
+
+        console.log('Started PipeWire graph monitoring (pw-mon)');
+    }
+
+    static stopMonitoring() {
+        if (this._monitorProcess) {
+            this._monitorProcess.kill();
+            this._monitorProcess = null;
+        }
+        clearTimeout(this._debounceTimer);
+        this._debounceTimer = null;
+        console.log('Stopped PipeWire graph monitoring');
+    }
 }
 
 module.exports = PipewireHelper;