fix: accept low-latency desktop move channel

docs/runbooks/webrtc-remote-desktop-white-screen-runbook.md

@@ -471,12 +471,14 @@ WebRTC RTP stats: packets=... packetDelta=1100 byteDelta=950000 writeErrors=0
 - `mouse_move` / hover 约 16ms 最多发送一次
 - 同一归一化坐标重复移动不发送
 - `mouse_down` 前强制发送最新坐标，保证点击命中
-- data channel `bufferedAmount` 过高时只丢弃 `mouse_move`
+- `mouse_move` 走独立 `input-move` data channel，配置为 unordered + 短 packet lifetime
+- 点击、键盘、滚轮走可靠有序 `input` data channel
+- `input-move` channel `bufferedAmount` 过高时只丢弃 `mouse_move`
 - `mouse_down`、`mouse_up`、`key_down`、`key_up`、`scroll` 不因背压丢弃
 
 判读：
 
-- 鼠标轨迹延迟但点击最终准确，通常是旧 `mouse_move` 事件排队。
+- 鼠标轨迹延迟但点击最终准确，通常是 `input-move` 背压或 Bridge 侧 mouse move coalescing 积压。
 - 点击也延迟或丢失，要查 data channel 状态、Bridge input injector、xdotool 写入。
 
 ### 3. 再看 Bridge input injector
@@ -484,13 +486,14 @@ WebRTC RTP stats: packets=... packetDelta=1100 byteDelta=950000 writeErrors=0
 Bridge 侧输入链路是：
 
 ```text
-APP Pointer/Key event -> WebRTC data channel -> Bridge OnDataChannel -> XdotoolInjector.Inject -> persistent xdotool stdin -> X11
+APP Pointer/Key event -> WebRTC input/input-move data channel -> Bridge OnDataChannel -> XdotoolInjector.Inject -> persistent xdotool stdin -> X11
 ```
 
 重点日志：
 
 ```text
 Data channel 'input'-'...' opened
+Data channel 'input-move'-'...' opened
 xdotool write error: ...
 xdotool mousemove write error: ...
 ```

internal/desktop/webrtc.go

@@ -13,6 +13,11 @@ import (
 	"github.com/pion/webrtc/v4"
 )
 
+const (
+	desktopReliableInputChannelLabel = "input"
+	desktopMoveInputChannelLabel     = "input-move"
+)
+
 type WebRTCServer struct {
 	peerConnection *webrtc.PeerConnection
 	videoTrack     *webrtc.TrackLocalStaticRTP
@@ -88,18 +93,24 @@ func (w *WebRTCServer) InitPeerConnection(iceServers []string) error {
 	// Handle Data Channel for inputs
 	pc.OnDataChannel(func(d *webrtc.DataChannel) {
 		log.Printf("Data channel '%s'-'%d' opened", d.Label(), d.ID())
-		if d.Label() == "input" {
-			d.OnMessage(func(msg webrtc.DataChannelMessage) {
-				var event InputEvent
-				if err := json.Unmarshal(msg.Data, &event); err != nil {
-					log.Printf("Failed to unmarshal input event: %v", err)
-					return
-				}
-				if err := w.inputInjector.Inject(event); err != nil {
-					log.Printf("Failed to inject input event: %v", err)
-				}
-			})
+		label := d.Label()
+		if !isDesktopInputDataChannelLabel(label) {
+			return
 		}
+		d.OnMessage(func(msg webrtc.DataChannelMessage) {
+			var event InputEvent
+			if err := json.Unmarshal(msg.Data, &event); err != nil {
+				log.Printf("Failed to unmarshal input event: %v", err)
+				return
+			}
+			if label == desktopMoveInputChannelLabel && event.Type != "mouse_move" {
+				log.Printf("Ignoring non-mouse_move input event on %s channel: %s", label, event.Type)
+				return
+			}
+			if err := w.inputInjector.Inject(event); err != nil {
+				log.Printf("Failed to inject input event: %v", err)
+			}
+		})
 	})
 
 	w.peerConnection = pc
@@ -108,6 +119,10 @@ func (w *WebRTCServer) InitPeerConnection(iceServers []string) error {
 	return nil
 }
 
+func isDesktopInputDataChannelLabel(label string) bool {
+	return label == desktopReliableInputChannelLabel || label == desktopMoveInputChannelLabel
+}
+
 // StartRTPReceiver listens on local UDP port for GStreamer RTP stream and forwards to WebRTC video track
 func (w *WebRTCServer) StartRTPReceiver(port int) error {
 	addr := fmt.Sprintf("127.0.0.1:%d", port)

internal/desktop/webrtc_test.go

@@ -0,0 +1,15 @@
+package desktop
+
+import "testing"
+
+func TestIsDesktopInputDataChannelLabelAllowsReliableAndMoveChannels(t *testing.T) {
+	if !isDesktopInputDataChannelLabel(desktopReliableInputChannelLabel) {
+		t.Fatalf("expected reliable input channel label to be accepted")
+	}
+	if !isDesktopInputDataChannelLabel(desktopMoveInputChannelLabel) {
+		t.Fatalf("expected mouse move input channel label to be accepted")
+	}
+	if isDesktopInputDataChannelLabel("debug") {
+		t.Fatalf("expected unrelated data channel label to be ignored")
+	}
+}