A car that keeps its screen is asked again with the display's channel named

The 2017 Pilot (protocol 1.0) never answered the request for its screen, even once the media
channel was open. The deprecated display field is what the 2018 Uconnect needed to give its
screen back, so the retry sends it too. The retry now also runs on cars with no media channel.

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipRunner.kt

@@ -1317,15 +1317,20 @@ class GearslipRunner(
         }
     }
 
-    /** Asks the car for its screen; the answer comes to [onVideoFocus]. */
-    private fun requestProjectedFocus() {
-        // VideoFocusRequestNotification { mode = 2; reason = 3 }. Reason 1 means "the phone's
-        // screen is off", which a 2020 Civic may have taken as a reason to keep its own
-        // screen (issue #43); 0 is UNKNOWN.
-        val focus = Protobuf.varintField(2, VIDEO_FOCUS_PROJECTED.toLong()) +
+    /**
+     * Asks the car for its screen; the answer comes to [onVideoFocus]. [withDisplay] names the
+     * display's channel too, as the request for the car's own screen does (see [requestNativeFocus]):
+     * the field is deprecated, but a car older than that may ignore a request without it.
+     */
+    private fun requestProjectedFocus(withDisplay: Boolean = false) {
+        // VideoFocusRequestNotification { disp_channel_id = 1; mode = 2; reason = 3 }. Reason 1
+        // means "the phone's screen is off", which a 2020 Civic may have taken as a reason to
+        // keep its own screen (issue #43); 0 is UNKNOWN.
+        val display = if (withDisplay) Protobuf.varintField(1, videoChannelId.toLong()) else ByteArray(0)
+        val focus = display + Protobuf.varintField(2, VIDEO_FOCUS_PROJECTED.toLong()) +
             Protobuf.varintField(3, 0L)
         send(MSG_VIDEO_FOCUS_REQUEST, focus, encrypted = true, channel = videoChannelId)
-        log.i("-> VideoFocusRequest(mode=PROJECTED)")
+        log.i(if (withDisplay) "-> VideoFocusRequest(display=$videoChannelId, mode=PROJECTED)" else "-> VideoFocusRequest(mode=PROJECTED)")
     }
 
     /**
@@ -1335,17 +1340,23 @@ class GearslipRunner(
      * music over Bluetooth that channel waits for the car to switch source, so if the screen
      * hasn't come a few seconds after asking, open it and ask again. Cars that hand the screen
      * straight over keep their own source as before.
+     * The 2017 Pilot (protocol 1.0) still kept its screen with the channel open, so the second
+     * request also names the display's channel, as cars of the Pilot's age may need.
      */
     private fun watchForWithheldScreen() {
         Thread({
             Thread.sleep(WITHHELD_SCREEN_MS)
             if (!running || videoStarted) return@Thread
-            val open = CarAudio.openSink ?: return@Thread
-            log.w("no screen from the car after ${WITHHELD_SCREEN_MS / 1000}s - opening the media channel and asking again")
-            open()
-            // Give the car the channel's open response before it hears the request again.
-            Thread.sleep(1_000)
-            if (running && !videoStarted) requestProjectedFocus()
+            val open = CarAudio.openSink
+            if (open != null) {
+                log.w("no screen from the car after ${WITHHELD_SCREEN_MS / 1000}s - opening the media channel and asking again")
+                open()
+                // Give the car the channel's open response before it hears the request again.
+                Thread.sleep(1_000)
+            } else {
+                log.w("no screen from the car after ${WITHHELD_SCREEN_MS / 1000}s - asking again")
+            }
+            if (running && !videoStarted) requestProjectedFocus(withDisplay = true)
         }, "gearslip-focus-fallback").apply { isDaemon = true }.start()
     }