android: add option for alternate head tracking packets (#176)

* Initial plan

* Add option for alternate head tracking packets

Co-authored-by: kavishdevar <46088622+kavishdevar@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: kavishdevar <46088622+kavishdevar@users.noreply.github.com>

android/app/src/main/java/me/kavishdevar/librepods/screens/AppSettingsScreen.kt

@@ -179,6 +179,10 @@ fun AppSettingsScreen(navController: NavController) {
         mutableStateOf(sharedPreferences.getBoolean("takeover_when_media_start", true))
     }
 
+    var useAlternateHeadTrackingPackets by remember {
+        mutableStateOf(sharedPreferences.getBoolean("use_alternate_head_tracking_packets", false))
+    }
+
     var mDensity by remember { mutableFloatStateOf(0f) }
 
     fun validateHexInput(input: String): Boolean {
@@ -1040,6 +1044,47 @@ fun AppSettingsScreen(navController: NavController) {
                     }
                 }
 
+                Row(
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .clickable(
+                            indication = null,
+                            interactionSource = remember { MutableInteractionSource() }
+                        ) {
+                            useAlternateHeadTrackingPackets = !useAlternateHeadTrackingPackets
+                            sharedPreferences.edit().putBoolean("use_alternate_head_tracking_packets", useAlternateHeadTrackingPackets).apply()
+                        },
+                    verticalAlignment = Alignment.CenterVertically
+                ) {
+                    Column(
+                        modifier = Modifier
+                            .weight(1f)
+                            .padding(vertical = 8.dp)
+                            .padding(end = 4.dp)
+                    ) {
+                        Text(
+                            text = "Use alternate head tracking packets",
+                            fontSize = 16.sp,
+                            color = textColor
+                        )
+                        Spacer(modifier = Modifier.height(4.dp))
+                        Text(
+                            text = "Enable this if head tracking doesn't work for you. This sends different data to AirPods for requesting/stopping head tracking data.",
+                            fontSize = 14.sp,
+                            color = textColor.copy(0.6f),
+                            lineHeight = 16.sp,
+                        )
+                    }
+
+                    StyledSwitch(
+                        checked = useAlternateHeadTrackingPackets,
+                        onCheckedChange = {
+                            useAlternateHeadTrackingPackets = it
+                            sharedPreferences.edit().putBoolean("use_alternate_head_tracking_packets", it).apply()
+                        }
+                    )
+                }
+
                 Row(
                     modifier = Modifier
                         .fillMaxWidth()

android/app/src/main/java/me/kavishdevar/librepods/services/AirPodsService.kt

@@ -1068,7 +1068,7 @@ class AirPodsService : Service(), SharedPreferences.OnSharedPreferenceChangeList
         if (isInCall) return
         if (config.headGestures) {
             initGestureDetector()
-            aacpManager.sendStartHeadTracking()
+            startHeadTracking()
             gestureDetector?.startDetection { accepted ->
                 if (accepted) {
                     answerCall()
@@ -2131,12 +2131,22 @@ class AirPodsService : Service(), SharedPreferences.OnSharedPreferenceChangeList
 
     fun startHeadTracking() {
         isHeadTrackingActive = true
-        aacpManager.sendStartHeadTracking()
+        val useAlternatePackets = sharedPreferences.getBoolean("use_alternate_head_tracking_packets", false)
+        if (useAlternatePackets) {
+            aacpManager.sendDataPacket(aacpManager.createAlternateStartHeadTrackingPacket())
+        } else {
+            aacpManager.sendStartHeadTracking()
+        }
         HeadTracking.reset()
     }
 
     fun stopHeadTracking() {
-        aacpManager.sendStopHeadTracking()
+        val useAlternatePackets = sharedPreferences.getBoolean("use_alternate_head_tracking_packets", false)
+        if (useAlternatePackets) {
+            aacpManager.sendDataPacket(aacpManager.createAlternateStopHeadTrackingPacket())
+        } else {
+            aacpManager.sendStopHeadTracking()
+        }
         isHeadTrackingActive = false
     }
 

android/app/src/main/java/me/kavishdevar/librepods/utils/AACPManager.kt

@@ -370,6 +370,14 @@ class AACPManager {
         return opcode + data
     }
 
+    fun createAlternateStartHeadTrackingPacket(): ByteArray {
+        val opcode = byteArrayOf(Opcodes.HEADTRACKING, 0x00)
+        val data = byteArrayOf(
+            0x00, 0x00, 0x10, 0x00, 0x0F, 0x00, 0x08, 0x73, 0x42, 0x0B, 0x08, 0x10, 0x10, 0x02, 0x1A, 0x05, 0x01, 0x40, 0x9C.toByte(), 0x00, 0x00
+        )
+        return opcode + data
+    }
+
     fun sendStopHeadTracking(): Boolean {
         return sendDataPacket(createStopHeadTrackingPacket())
     }
@@ -382,6 +390,14 @@ class AACPManager {
         return opcode + data
     }
 
+    fun createAlternateStopHeadTrackingPacket(): ByteArray {
+        val opcode = byteArrayOf(Opcodes.HEADTRACKING, 0x00)
+        val data = byteArrayOf(
+            0x00, 0x00, 0x10, 0x00, 0x0F, 0x00, 0x08, 0x75, 0x42, 0x0B, 0x08, 0x10, 0x10, 0x02, 0x1A, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00
+        )
+        return opcode + data
+    }
+
     fun sendRename(name: String): Boolean {
         return sendDataPacket(createRenamePacket(name))
     }