fix(vnc-watcher): detect Xvfb display when launched with -displayfd

[paranoidi]

Disclaimer: PR made with AI but I verified locally that it fixes the issue for me.

Bug Description

When Camofox runs with VNC enabled (ENABLE_VNC=1), noVNC fails with "Failed to connect to 127.0.0.1:5900: Connection refused" because x11vnc never starts. The VNC watcher script loops forever unable to detect the Xvfb display.
Root Cause

The VNC watcher script uses the awk regex /\Xvfb :[0-9]+/ to find Xvfb, which only matches when Xvfb is launched with a hardcoded display number (e.g. Xvfb :0 -screen ...). The camoufox-js VirtualDisplay class launches Xvfb with -displayfd 3 (dynamic display assignment), so the command line looks like Xvfb -displayfd 3 -screen ... — no :0 in argv. The watcher never finds it, x11vnc never attaches, and noVNC stays permanently disconnected.
Fix

Replace the inline awk detection with a detect_display() function that tries three fallbacks in order:

1. Xvfb with hardcoded :N display in argv (original method, regex relaxed to /\Xvfb /)
2. /tmp/.X*-lock files — the traditional X lock file that contains the display number
3. /tmp/.X* sockets — fallback via /tmp/.X11-unix/X* files when no lock file exists

How to Verify

1. Start with ENABLE_VNC=1: docker run -d -p 9377:9377 -p 6080:6080 -p 5901:5900 -e ENABLE_VNC=1 camofox-browser:135.0.1-x86_64
2. Wait for the browser to pre-warm (check curl http://localhost:9377/health for browserConnected:true)
3. Open http://localhost:6080/vnc.html in a browser and click Connect
4. Confirm you see the Camofox browser window live

[gearwave00001]

This was also an issue for me with noVNC.html and was resolved in a similar way. My agent performed similar fixes plus a few additions so I ran it against your PR to combine.

Here's the full diff against the original vnc-watcher.sh:

diff
 #!/bin/sh
VNC watcher: detects Camoufox's dynamically-assigned Xvfb display and attaches
x11vnc + noVNC to it. Handles browser restarts (re-attaches on display change).

 set -e

 VNC_PORT="${VNC_PORT:-5900}"
 NOVNC_PORT="${NOVNC_PORT:-6080}"
 VNC_RESOLUTION="${VNC_RESOLUTION:-1920x1080x24}"

 log() { printf '[vnc-watcher] %s\n' "$*" >&2; }

 CURRENT_DISPLAY=""
 X11VNC_PID=""

Prepare password file if requested
 PASSFILE=""
 if [ -n "${VNC_PASSWORD:-}" ]; then
   mkdir -p /tmp/.vnc
   x11vnc -storepasswd "$VNC_PASSWORD" /tmp/.vnc/passwd >/dev/null 2>&1
   PASSFILE="/tmp/.vnc/passwd"
   log "x11vnc: password protected"
 else
   log "x11vnc: NO password (bind $NOVNC_PORT to $VNC_BIND on host)"
 fi

Start noVNC (websockify)
 NOVNC_DIR="/usr/share/novnc"
 if [ ! -d "$NOVNC_DIR" ]; then
   log "ERROR: $NOVNC_DIR not found; noVNC cannot start"
   exit 1
 fi
 VNC_BIND="${VNC_BIND:-127.0.0.1}"
 log "Starting noVNC (websockify) on $VNC_BIND:$NOVNC_PORT -> 127.0.0.1:$VNC_PORT"
 websockify --web "$NOVNC_DIR" "$VNC_BIND:$NOVNC_PORT" "127.0.0.1:$VNC_PORT" >/var/log/novnc.log 2>&1 &

+# detect_display - tries multiple methods to find the Xvfb display number
+detect_display() {
+  # Method 1: Xvfb with hardcoded :N in argv (original method)
+  _found=$(ps -eo args= 2>/dev/null | awk '/\/Xvfb / { for(i=1;i<=NF;i++) if($i ~ /^:[0-9]+$/) {print $i; exit} }' | head -1)
+  if [ -n "$_found" ]; then
+    echo "$_found"
+    return
+  fi
+
+  # Method 2: /tmp/.X*-lock files (works with -displayfd mode)
+  for _lock in /tmp/.X*-lock; do
+    if [ -f "$_lock" ]; then
+      _num=$(basename "$_lock" | sed 's/^\.X//')
+      echo ":$_num"
+      return
+    fi
+  done
+
+  # Method 3: /tmp/.X11-unix/X* sockets
+  for _sock in /tmp/.X11-unix/X*; do
+    if [ -S "$_sock" ] || [ -e "$_sock" ]; then
+      _num=$(basename "$_sock" | sed 's/^X//')
+      echo ":$_num"
+      return
+    fi
+  done
+}

 log "VNC watcher started -- will attach x11vnc when Camoufox's Xvfb appears"

 while true; do
-  # Find Xvfb with our patched resolution
-  FOUND=$(ps -eo args= 2>/dev/null | awk -v res="$VNC_RESOLUTION" '
-    /\/Xvfb :[0-9]+/ && index($0, res) {
-      for (i=1;i<=NF;i++) if ($i ~ /^:[0-9]+$/) { print $i; exit }
-    }
-  ' | head -1)
+  FOUND=$(detect_display)

   if [ -n "$FOUND" ] && [ "$FOUND" != "$CURRENT_DISPLAY" ]; then
     # New or changed display -- (re)attach x11vnc
     if [ -n "$X11VNC_PID" ] && kill -0 "$X11VNC_PID" 2>/dev/null; then
       log "Camoufox display changed ($CURRENT_DISPLAY -> $FOUND), restarting x11vnc"
       kill "$X11VNC_PID" 2>/dev/null || true
       sleep 0.5
     fi

     CURRENT_DISPLAY="$FOUND"
     log "Attaching x11vnc to DISPLAY=$CURRENT_DISPLAY"

+    # Poll xdpyinfo until the display accepts connections
+    for _wait in 1 2 3 4 5; do
+      if xdpyinfo -display "$CURRENT_DISPLAY" >/dev/null 2>&1; then
+        break
+      fi
+      sleep 1
+    done

-    X11VNC_ARGS="-display $CURRENT_DISPLAY -forever -shared -rfbport $VNC_PORT -noxdamage -quiet -bg -o /var/log/x11vnc.log"
+    X11VNC_ARGS="-display $CURRENT_DISPLAY -forever -shared -rfbport $VNC_PORT -quiet -bg -o /var/log/x11vnc.log"
     [ "${VIEW_ONLY:-0}" = "1" ] && X11VNC_ARGS="$X11VNC_ARGS -viewonly"
     if [ -n "$PASSFILE" ]; then
       X11VNC_ARGS="$X11VNC_ARGS -rfbauth $PASSFILE"
     else
       X11VNC_ARGS="$X11VNC_ARGS -nopw"
     fi

-    x11vnc $X11VNC_ARGS || true
+    x11vnc $X11VNC_ARGS || {
+      log "x11vnc failed to start, retrying in 2 seconds..."
+      sleep 2
+      x11vnc $X11VNC_ARGS || true
+    }
     sleep 1
     X11VNC_PID=$(pgrep -f "x11vnc.*-display $CURRENT_DISPLAY" | head -1)
     log "x11vnc running (pid=$X11VNC_PID) on DISPLAY=$CURRENT_DISPLAY"
   fi

   sleep 2
 done

From PR #5243 (paranoidi):

• detect_display() function with 3 fallback methods (argv, lock files, X11-unix sockets)
• Replaces the broken awk regex //Xvfb :[0-9]+/ that only matched hardcoded :0

My additions:

• xdpyinfo polling loop — waits up to 5 seconds for X display to accept connections before starting x11vnc (prevents XIO error crash)
• x11vnc retry logic — if first attempt fails, retries once after 2 seconds
• Removed -noxdamage flag (can cause issues with some X servers)
• Fixed basename parsing for /tmp/.X11-unix/X* sockets (was returning :X0 instead of :0)
• Replaced local bash-isms with prefixed variables (_found, _num, etc.) for dash compatibility

[skyfallsin]

Thank you — support for Xvfb launched with -displayfd has shipped in v1.12.1. The released implementation resolves the display through the owned Xvfb PID using lock files when available and /proc socket ownership when lock files are absent, avoiding attachment to another Camofox server’s display.

Included via commit 50b5031 with co-author credit.