App exit diagnostics, desktop file discovery, WiFi wpa_supplicant fix

- Capture stderr from GUI apps and show meaningful exit reasons (signal names,
  error messages) instead of generic "Application exited"
- Add /api/display/discover-apps endpoint that scans .desktop files for
  installed GUI apps, replacing manual-only app configuration
- Settings > Applications now shows discoverable apps with one-click Add,
  with manual form available as fallback
- Fix WiFi: start wpa_supplicant before bringing interface up, handle rfkill
  blocks, add retry logic and error messages to scan results
- Fix WiFi scan frontend bug: response is {networks:[...]} not a bare array
- Add iw and wpasupplicant to install.sh dependencies

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

backend/display.py

@@ -90,7 +90,10 @@ class ManagedGuiApp:
     target_fps: int = 10
     created_at: float = field(default_factory=time.time)
     last_frame: Optional[bytes] = field(default=None, repr=False)
+    exit_reason: Optional[str] = field(default=None, repr=False)
     _capture_task: Optional[asyncio.Task] = field(default=None, repr=False)
+    _stderr_task: Optional[asyncio.Task] = field(default=None, repr=False)
+    _stderr_lines: list = field(default_factory=list, repr=False)
     _websockets: list = field(default_factory=list, repr=False)
     _streaming: bool = field(default=False, repr=False)
 
@@ -128,6 +131,26 @@ class ManagedGuiApp:
     def start_capture(self):
         if self._capture_task is None or self._capture_task.done():
             self._capture_task = asyncio.create_task(self._capture_loop())
+        if self._stderr_task is None or self._stderr_task.done():
+            self._stderr_task = asyncio.create_task(self._read_stderr())
+
+    async def _read_stderr(self):
+        """Read stderr in background, keep last N lines for exit diagnostics."""
+        if not self.process or not self.process.stderr:
+            return
+        try:
+            while True:
+                line = await self.process.stderr.readline()
+                if not line:
+                    break
+                decoded = line.decode(errors="replace").rstrip()
+                if decoded:
+                    self._stderr_lines.append(decoded)
+                    # Keep only last 20 lines
+                    if len(self._stderr_lines) > 20:
+                        self._stderr_lines = self._stderr_lines[-20:]
+        except Exception:
+            pass
 
     async def _capture_loop(self):
         """Background: capture window pixmap → JPEG → fan-out."""
@@ -173,14 +196,56 @@ class ManagedGuiApp:
                 break
             await asyncio.sleep(1.0 / self.target_fps)
 
-        # Process exited — notify viewers
+        # Process exited — build exit reason from stderr + return code
+        exit_msg = self._build_exit_reason()
+        self.exit_reason = exit_msg
+        log.info("App %s exited: %s", self.app_id, exit_msg)
+
         for ws in list(self._websockets):
             try:
-                await ws.send_json({"type": "closed", "data": "Application exited"})
+                await ws.send_json({"type": "closed", "data": exit_msg})
             except Exception:
                 pass
         log.info("Capture loop ended for app %s", self.app_id)
 
+    def _build_exit_reason(self) -> str:
+        """Build a human-readable exit reason from stderr output and return code."""
+        rc = self.process.returncode if self.process else None
+        # Filter stderr for meaningful error lines
+        error_hints = []
+        for line in self._stderr_lines:
+            low = line.lower()
+            # Skip noisy Qt/GTK debug lines
+            if any(skip in low for skip in ("qt.qpa.xcb: qxcb", "libgl", "mesa",
+                                             "dbind-warning", "g_dbus", "gtk-warning")):
+                continue
+            # Keep lines with error-like keywords
+            if any(kw in low for kw in ("error", "fatal", "failed", "abort",
+                                         "cannot", "could not", "not found",
+                                         "no such", "missing", "permission denied",
+                                         "segfault", "signal", "killed", "crash")):
+                error_hints.append(line)
+
+        if error_hints:
+            # Show last few relevant error lines
+            hint_text = "\n".join(error_hints[-5:])
+            if rc is not None and rc < 0:
+                sig = abs(rc)
+                return f"Killed by signal {sig}\n{hint_text}"
+            return hint_text
+
+        # No meaningful stderr — use return code
+        if rc is None:
+            return "Application exited unexpectedly"
+        if rc == 0:
+            return "Application closed normally"
+        if rc < 0:
+            sig = abs(rc)
+            sig_names = {6: "SIGABRT", 9: "SIGKILL", 11: "SIGSEGV", 15: "SIGTERM"}
+            sig_name = sig_names.get(sig, f"signal {sig}")
+            return f"Crashed ({sig_name})"
+        return f"Exited with code {rc}"
+
     async def _capture_frame(self) -> Optional[bytes]:
         """Capture window as JPEG using ImageMagick import."""
         if not self.window_id or not IMPORT_BIN:
@@ -321,7 +386,7 @@ class ManagedGuiApp:
                 pass
 
     def to_dict(self) -> dict:
-        return {
+        d = {
             "app_id": self.app_id,
             "command": self.command,
             "title": self.title,
@@ -332,6 +397,9 @@ class ManagedGuiApp:
             "viewers": len(self._websockets),
             "created_at": self.created_at,
         }
+        if self.exit_reason:
+            d["exit_reason"] = self.exit_reason
+        return d
 
 
 # ---------------------------------------------------------------------------

backend/routers/display.py

@@ -5,6 +5,10 @@ receives JPEG frames, sends input events. REST endpoints manage app lifecycle.
 """
 
 import logging
+import os
+import re
+import shutil
+from pathlib import Path
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Query, WebSocket, WebSocketDisconnect
@@ -85,6 +89,131 @@ async def display_status(user: str = Depends(get_current_user)):
     }
 
 
+# ---------------------------------------------------------------------------
+# Desktop file discovery — find installed GUI apps
+# ---------------------------------------------------------------------------
+
+_DESKTOP_DIRS = [
+    Path("/usr/share/applications"),
+    Path("/usr/local/share/applications"),
+    Path(os.path.expanduser("~/.local/share/applications")),
+    Path("/var/lib/flatpak/exports/share/applications"),
+    Path(os.path.expanduser("~/.local/share/flatpak/exports/share/applications")),
+    Path("/snap/applications"),
+]
+
+# Categories that indicate a docked/GUI application
+_GUI_CATEGORIES = {
+    "network", "webbrowser", "email", "office", "graphics", "audio", "video",
+    "chat", "instantmessaging", "filetransfer", "p2p", "remoteaccess",
+    "viewer", "player", "game", "utility", "system", "settings",
+    "monitor", "filesystem", "security", "accessibility",
+}
+
+# Commands to exclude (system utilities, terminals, etc.)
+_EXCLUDED_CMDS = {
+    "bash", "sh", "zsh", "fish", "xterm", "xfce4-terminal", "gnome-terminal",
+    "lxterminal", "urxvt", "alacritty", "kitty", "foot",
+    "true", "false", "update-manager", "software-properties-gtk",
+}
+
+
+def _parse_desktop_file(path: Path) -> Optional[dict]:
+    """Parse a .desktop file and return app info, or None if not a GUI app."""
+    try:
+        content = path.read_text(errors="replace")
+    except Exception:
+        return None
+
+    entry = {}
+    in_desktop_entry = False
+
+    for line in content.splitlines():
+        line = line.strip()
+        if line == "[Desktop Entry]":
+            in_desktop_entry = True
+            continue
+        if line.startswith("[") and line.endswith("]"):
+            if in_desktop_entry:
+                break  # End of [Desktop Entry] section
+            continue
+        if not in_desktop_entry or "=" not in line:
+            continue
+        key, _, value = line.partition("=")
+        key = key.strip()
+        value = value.strip()
+        if key in ("Name", "Exec", "Icon", "Type", "NoDisplay", "Hidden",
+                    "Categories", "Terminal", "Comment"):
+            entry[key] = value
+
+    # Must be Type=Application
+    if entry.get("Type") != "Application":
+        return None
+    # Skip hidden/no-display
+    if entry.get("NoDisplay", "").lower() == "true":
+        return None
+    if entry.get("Hidden", "").lower() == "true":
+        return None
+    # Skip terminal apps
+    if entry.get("Terminal", "").lower() == "true":
+        return None
+
+    exec_line = entry.get("Exec", "")
+    if not exec_line:
+        return None
+
+    # Extract command: remove field codes (%u, %U, %f, %F, etc.)
+    exec_clean = re.sub(r"%[a-zA-Z]", "", exec_line).strip()
+    # Get first token as command, strip path
+    parts = exec_clean.split()
+    if not parts:
+        return None
+    command = os.path.basename(parts[0])
+
+    if command in _EXCLUDED_CMDS or not command:
+        return None
+
+    # Check the command actually exists
+    if not shutil.which(command):
+        return None
+
+    # Parse categories
+    categories = set()
+    if entry.get("Categories"):
+        categories = {c.strip().lower() for c in entry["Categories"].split(";")}
+
+    name = entry.get("Name", command)
+    icon = entry.get("Icon", "🖥")
+    comment = entry.get("Comment", "")
+
+    return {
+        "name": name,
+        "command": command,
+        "icon": icon,
+        "comment": comment,
+        "categories": sorted(categories - {""}),
+        "desktop_file": path.name,
+    }
+
+
+@router.get("/discover-apps")
+async def discover_apps(_user: str = Depends(get_current_user)):
+    """Scan .desktop files for installed GUI applications."""
+    apps = {}
+
+    for d in _DESKTOP_DIRS:
+        if not d.is_dir():
+            continue
+        for f in d.glob("*.desktop"):
+            app = _parse_desktop_file(f)
+            if app and app["command"] not in apps:
+                apps[app["command"]] = app
+
+    # Sort alphabetically
+    result = sorted(apps.values(), key=lambda a: a["name"].lower())
+    return result
+
+
 # ---------------------------------------------------------------------------
 # WebSocket — frame streaming + input
 # ---------------------------------------------------------------------------

backend/routers/network.py

@@ -744,6 +744,11 @@ async def configure_interface(
         wifi_password=cfg.wifi_password or "",
     )
 
+    # For wireless interfaces, handle wpa_supplicant
+    is_wireless = Path(f"/sys/class/net/{name}/wireless").exists()
+    if is_wireless and cfg.ssid:
+        await _start_wpa_supplicant(name)
+
     # Apply: bring interface down then up
     # Use ifdown/ifup if available, else ip commands
     ifdown = _find_bin("ifdown")
@@ -832,6 +837,50 @@ network={{
     log.info("Wrote wpa_supplicant config for %s: ssid=%s", iface, ssid)
 
 
+async def _start_wpa_supplicant(iface: str):
+    """Start wpa_supplicant for a wireless interface.
+
+    Kills any existing instance for this interface first.
+    """
+    wpa_bin = _find_bin("wpa_supplicant")
+    if not wpa_bin:
+        log.warning("wpa_supplicant not found — WiFi auth will not work")
+        return
+
+    conf_file = _WPA_SUPPLICANT_DIR / f"{iface}.conf"
+    if not conf_file.exists():
+        log.warning("No wpa_supplicant config for %s", iface)
+        return
+
+    # Kill any existing wpa_supplicant for this interface
+    killall = _find_bin("killall")
+    pkill = _find_bin("pkill")
+    if pkill:
+        await _run_cmd(pkill, "-f", f"wpa_supplicant.*{iface}", timeout=5)
+    elif killall:
+        await _run_cmd(killall, "wpa_supplicant", timeout=5)
+
+    await asyncio.sleep(0.5)
+
+    # Bring interface up first
+    await _run_cmd(_IP_BIN, "link", "set", iface, "up")
+
+    # Start wpa_supplicant in background
+    rc, _, stderr = await _run_cmd(
+        wpa_bin, "-B",  # background/daemonize
+        "-i", iface,
+        "-c", str(conf_file),
+        "-D", "nl80211,wext",  # try nl80211 first, fallback to wext
+        timeout=10,
+    )
+    if rc != 0:
+        log.warning("wpa_supplicant failed for %s: %s", iface, stderr.strip())
+    else:
+        log.info("wpa_supplicant started for %s", iface)
+        # Wait a moment for association
+        await asyncio.sleep(2)
+
+
 @router.get("/wifi/scan/{name}")
 async def scan_wifi(name: str, _user: str = Depends(get_current_user)):
     """Scan for WiFi networks using iw or iwlist (no NetworkManager required)."""
@@ -841,28 +890,56 @@ async def scan_wifi(name: str, _user: str = Depends(get_current_user)):
     if not Path(f"/sys/class/net/{name}/wireless").exists():
         raise HTTPException(400, f"{name} is not a wireless interface")
 
+    # Check if interface is rfkill blocked
+    rfkill = _find_bin("rfkill")
+    if rfkill:
+        rc, stdout, _ = await _run_cmd(rfkill, "list", "wifi", timeout=5)
+        if rc == 0 and "Soft blocked: yes" in stdout:
+            # Try to unblock
+            await _run_cmd(rfkill, "unblock", "wifi", timeout=5)
+            await asyncio.sleep(0.5)
+
     networks = []
+    last_error = ""
+
+    # Bring interface up first — scan requires it
+    await _run_cmd(_IP_BIN, "link", "set", name, "up")
+    await asyncio.sleep(0.5)
 
     # Try iw first
     if _IW_BIN:
-        rc, stdout, _ = await _run_cmd(_IW_BIN, "dev", name, "scan", timeout=15)
+        rc, stdout, stderr = await _run_cmd(_IW_BIN, "dev", name, "scan", timeout=20)
         if rc == 0:
             networks = _parse_iw_scan(stdout)
-        elif rc != 0:
-            # May need to bring interface up first
-            await _run_cmd(_IP_BIN, "link", "set", name, "up")
-            await asyncio.sleep(1)
-            rc, stdout, _ = await _run_cmd(_IW_BIN, "dev", name, "scan", timeout=15)
+        else:
+            last_error = stderr.strip()
+            log.warning("iw scan failed for %s: %s", name, last_error)
+            # Retry once after a brief wait (scan can fail if device is busy)
+            await asyncio.sleep(2)
+            rc, stdout, stderr = await _run_cmd(_IW_BIN, "dev", name, "scan", timeout=20)
             if rc == 0:
                 networks = _parse_iw_scan(stdout)
+            else:
+                last_error = stderr.strip()
+                log.warning("iw scan retry failed for %s: %s", name, last_error)
 
     # Fallback: iwlist
     if not networks:
         iwlist = _find_bin("iwlist")
         if iwlist:
-            rc, stdout, _ = await _run_cmd(iwlist, name, "scan", timeout=15)
+            rc, stdout, stderr = await _run_cmd(iwlist, name, "scan", timeout=15)
             if rc == 0:
                 networks = _parse_iwlist_scan(stdout)
+            else:
+                last_error = stderr.strip() or last_error
+                log.warning("iwlist scan failed for %s: %s", name, last_error)
+
+    if not networks and not _IW_BIN and not _find_bin("iwlist"):
+        return {"networks": [], "error": "Neither iw nor iwlist found. Install: apt-get install iw wireless-tools"}
+
+    if not networks and last_error:
+        # Return empty with error context
+        return {"networks": [], "error": last_error}
 
     return {"networks": networks}
 

frontend/css/apps/display.css

@@ -72,3 +72,17 @@
 .gui-status.exited .gui-status-icon {
     opacity: 0.7;
 }
+
+.gui-status.exited .gui-status-text,
+.gui-status.error .gui-status-text {
+    max-width: 600px;
+    font-size: 12px;
+    line-height: 1.5;
+    text-align: left;
+    background: rgba(0,0,0,0.3);
+    padding: 12px 16px;
+    border-radius: var(--radius-md);
+    border: 1px solid var(--border-structural);
+    word-break: break-word;
+    white-space: pre-wrap;
+}

frontend/css/apps/settings.css

@@ -357,6 +357,36 @@
     cursor: pointer;
 }
 
+/* App discovery list */
+.app-discover-list {
+    max-height: 300px;
+    overflow-y: auto;
+    -webkit-overflow-scrolling: touch;
+}
+
+.app-discover-item {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: 12px;
+    padding: 10px 0;
+    border-bottom: 1px solid var(--border-structural);
+}
+
+.app-discover-item:last-child {
+    border-bottom: none;
+}
+
+.app-manual-form {
+    margin-top: 16px;
+    padding-top: 16px;
+    border-top: 1px dashed var(--border-structural);
+}
+
+.app-manual-form.hidden {
+    display: none;
+}
+
 /* WiFi network list */
 .wifi-network-list {
     max-height: 360px;

frontend/js/apps/display.js

@@ -188,9 +188,12 @@
         state.statusEl.className = 'gui-status ' + type;
 
         const icons = { connecting: '🖥', error: '⚠', exited: '✖' };
+        // Escape HTML and preserve newlines for multiline error messages
+        const escaped = text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+        const formatted = escaped.replace(/\n/g, '<br>');
         state.statusEl.innerHTML = `
             <div class="gui-status-icon">${icons[type] || '🖥'}</div>
-            <div class="gui-status-text">${text}</div>
+            <div class="gui-status-text">${formatted}</div>
         `;
     }
 

frontend/js/apps/settings.js

@@ -470,11 +470,14 @@
                 try {
                     const res = await Atlus.apiFetch(`/api/network/wifi/scan/${name}`);
                     if (!res.ok) {
-                        resultsEl.innerHTML = '<div class="net-error">Failed to scan WiFi networks</div>';
+                        const err = await res.json().catch(() => ({}));
+                        resultsEl.innerHTML = `<div class="net-error">Failed to scan: ${err.detail || 'Unknown error'}</div>`;
                     } else {
-                        const networks = await res.json();
+                        const data = await res.json();
+                        const networks = data.networks || [];
                         if (networks.length === 0) {
-                            resultsEl.innerHTML = '<div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">No networks found</div>';
+                            const errMsg = data.error ? `<br><span style="font-size:11px;">${data.error}</span>` : '';
+                            resultsEl.innerHTML = `<div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">No networks found${errMsg}</div>`;
                         } else {
                             resultsEl.innerHTML = '';
                             for (const net of networks) {
@@ -908,10 +911,17 @@
         }
         html += '</div>';
 
-        // Add app form
+        // Discover installed apps
         html += `
             <div class="settings-group">
                 <div class="settings-group-title">ADD APPLICATION</div>
+                <div id="appDiscoverList" class="app-discover-list">
+                    <div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">Loading installed apps…</div>
+                </div>
+                <div style="margin-top:12px;">
+                    <button class="settings-btn secondary" id="appAddManualToggle" style="font-size:12px;">+ Add manually</button>
+                </div>
+                <div id="appAddManualForm" class="app-manual-form hidden">
                     <div class="settings-row">
                         <div><div class="settings-row-label">Name</div><div class="settings-row-desc">Display name for the app</div></div>
                         <input class="settings-input" id="appAddName" placeholder="e.g. Nextcloud">
@@ -921,7 +931,7 @@
                         <input class="settings-input" id="appAddCommand" placeholder="e.g. nextcloud">
                     </div>
                     <div class="settings-row">
-                    <div><div class="settings-row-label">Icon</div><div class="settings-row-desc">Emoji icon for dock and panel</div></div>
+                        <div><div class="settings-row-label">Icon</div><div class="settings-row-desc">Emoji icon for panel</div></div>
                         <input class="settings-input" id="appAddIcon" value="🖥" style="width:80px;text-align:center;">
                     </div>
                     <div class="settings-row">
@@ -943,6 +953,7 @@
                         <button class="settings-btn" id="appAddSave">Add Application</button>
                     </div>
                 </div>
+            </div>
         `;
 
         contentEl.innerHTML = html;
@@ -981,7 +992,13 @@
             });
         });
 
-        // Add app
+        // Manual form toggle
+        contentEl.querySelector('#appAddManualToggle').addEventListener('click', () => {
+            const form = contentEl.querySelector('#appAddManualForm');
+            form.classList.toggle('hidden');
+        });
+
+        // Manual add
         contentEl.querySelector('#appAddSave').addEventListener('click', async () => {
             const name = contentEl.querySelector('#appAddName').value.trim();
             const command = contentEl.querySelector('#appAddCommand').value.trim();
@@ -995,7 +1012,6 @@
                 return;
             }
 
-            // Check for duplicate command
             if (guiApps.some(a => a.command === command)) {
                 alert(`An application with command "${command}" already exists.`);
                 return;
@@ -1020,6 +1036,80 @@
             _refreshPanel();
             renderApplications();
         });
+
+        // Load discovered apps
+        _loadDiscoverableApps(guiApps);
+    }
+
+    async function _loadDiscoverableApps(existingApps) {
+        const listEl = contentEl.querySelector('#appDiscoverList');
+        if (!listEl) return;
+
+        try {
+            const res = await Atlus.apiFetch('/api/display/discover-apps');
+            if (!res.ok) {
+                listEl.innerHTML = '<div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">Could not scan for installed apps</div>';
+                return;
+            }
+            const discovered = await res.json();
+
+            // Filter out apps already configured
+            const existingCmds = new Set(existingApps.map(a => a.command));
+            const available = discovered.filter(a => !existingCmds.has(a.command));
+
+            if (available.length === 0) {
+                listEl.innerHTML = '<div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">No additional applications found on this system</div>';
+                return;
+            }
+
+            listEl.innerHTML = '';
+            for (const app of available) {
+                const row = document.createElement('div');
+                row.className = 'app-discover-item';
+                row.innerHTML = `
+                    <div class="app-config-info">
+                        <span class="app-config-icon">${_desktopIcon(app.icon)}</span>
+                        <div class="app-config-details">
+                            <div class="app-config-name">${app.name}</div>
+                            <div class="app-config-cmd">${app.command}${app.comment ? ' — ' + app.comment : ''}</div>
+                        </div>
+                    </div>
+                    <button class="settings-btn" style="height:28px;font-size:11px;padding:0 14px;flex-shrink:0;">Add</button>
+                `;
+                row.querySelector('.settings-btn').addEventListener('click', async () => {
+                    const newApp = {
+                        id: _slugify(app.name),
+                        name: app.name,
+                        command: app.command,
+                        icon: _desktopIcon(app.icon),
+                        args: [],
+                        target_fps: 10,
+                        autostart: false,
+                    };
+                    const apps = [...existingApps, newApp];
+                    await Atlus.apiFetch('/api/settings', {
+                        method: 'PUT',
+                        body: { gui_apps: apps },
+                    });
+                    _refreshPanel();
+                    renderApplications();
+                });
+                listEl.appendChild(row);
+            }
+        } catch (e) {
+            listEl.innerHTML = '<div style="padding:8px 0;color:var(--text-muted);font-family:var(--font-mono);font-size:12px;">Failed to scan for apps</div>';
+        }
+    }
+
+    function _desktopIcon(icon) {
+        // If it's already an emoji or short text, use it directly
+        // If it's a path or icon name (from .desktop files), use a default emoji
+        if (!icon) return '🖥';
+        // Emoji detection: if first char is > U+2000, likely an emoji
+        if (icon.codePointAt(0) > 0x2000) return icon;
+        // Short text like "A" or icon names like "nextcloud" — use default
+        if (icon.length <= 3 && !icon.includes('/')) return icon;
+        return '🖥';
     }
 
     async function renderServicesConfig() {

install.sh

@@ -53,6 +53,8 @@ install_deps() {
         imagemagick \
         x11-utils \
         libxcb-cursor0 \
+        iw \
+        wpasupplicant \
         > /dev/null 2>&1
     ok "System dependencies installed."
 }