From 1a52f19b329e770fff984ffa4e9964599d077624 Mon Sep 17 00:00:00 2001
From: eagleeyetom <tomek.kondrat@gmail.com>
Date: Thu, 27 Nov 2025 00:32:33 +0100
Subject: [PATCH] Android cast: stabilize MediaSession volume handling;
 simplify Google Cast volume

---
 .../audiobookshelf/app/player/CastPlayer.kt   | 41 +++++++++++++++----
 .../app/player/PlayerNotificationService.kt   | 31 +++++---------
 2 files changed, 42 insertions(+), 30 deletions(-)

diff --git a/android/app/src/main/java/com/audiobookshelf/app/player/CastPlayer.kt b/android/app/src/main/java/com/audiobookshelf/app/player/CastPlayer.kt
index 9f7f59f9..a31bacf4 100644
--- a/android/app/src/main/java/com/audiobookshelf/app/player/CastPlayer.kt
+++ b/android/app/src/main/java/com/audiobookshelf/app/player/CastPlayer.kt
@@ -3,6 +3,7 @@ package com.audiobookshelf.app.player
 import android.annotation.SuppressLint
 import android.os.Looper
 import android.util.Log
+import kotlin.math.roundToInt
 import android.view.Surface
 import android.view.SurfaceHolder
 import android.view.SurfaceView
@@ -53,6 +54,10 @@ class CastPlayer(var castContext: CastContext) : BasePlayer() {
   private var myCurrentTrackGroups: TrackGroupArray
   private var myCurrentTrackSelections: TrackSelectionArray
 
+  // Cache for pending volume to handle async setVolume
+  private var pendingVolume: Int? = null
+  private var pendingVolumeSetAt: Long = 0L
+
   var currentMediaItems:List<MediaItem> = mutableListOf()
   var remoteMediaClient:RemoteMediaClient? = null
   var sessionAvailabilityListener:SessionAvailabilityListener? = null
@@ -864,12 +869,24 @@ class CastPlayer(var castContext: CastContext) : BasePlayer() {
   }
 
   override fun getDeviceVolume(): Int {
+    // Short-lived cache without even-value quantization
+    val now = System.currentTimeMillis()
+    if (pendingVolume != null && (now - pendingVolumeSetAt) < 100) {
+      return pendingVolume!!
+    }
+
     val session = castContext.sessionManager.currentCastSession
-    return if (session != null && !session.isMute) {
-      (session.volume * 100).toInt()
+    val vol = if (session != null && !session.isMute) {
+      (session.volume * 100).roundToInt().coerceIn(0, 100)
     } else {
       0
     }
+
+    if (pendingVolume != null && vol == pendingVolume) {
+      pendingVolume = null
+    }
+
+    return vol
   }
 
   override fun isDeviceMuted(): Boolean {
@@ -881,22 +898,28 @@ class CastPlayer(var castContext: CastContext) : BasePlayer() {
     val session = castContext.sessionManager.currentCastSession
     try {
       val clamped = volume.coerceIn(0, 100)
-      session?.volume = clamped / 100.0
+      val target = (clamped / 100.0).let { kotlin.math.round(it * 100.0) / 100.0 }
+
+      // Cache for 100ms to return in getDeviceVolume during async period
+      pendingVolume = clamped
+      pendingVolumeSetAt = System.currentTimeMillis()
+
+      session?.setVolume(target)
     } catch (e: Exception) {
       Log.e(tag, "Failed to set cast device volume", e)
     }
   }
 
   override fun increaseDeviceVolume() {
-    val currentVolume = getDeviceVolume()
-    val newVolume = (currentVolume + 1).coerceAtMost(100)
-    setDeviceVolume(newVolume)
+    val current = getDeviceVolume()
+    val next = current + 1
+    setDeviceVolume(next.coerceAtMost(100))
   }
 
   override fun decreaseDeviceVolume() {
-    val currentVolume = getDeviceVolume()
-    val newVolume = (currentVolume - 1).coerceAtLeast(0)
-    setDeviceVolume(newVolume)
+    val current = getDeviceVolume()
+    val next = current - 1
+    setDeviceVolume(next.coerceAtLeast(0))
   }
 
   override fun setDeviceMuted(muted: Boolean) {
diff --git a/android/app/src/main/java/com/audiobookshelf/app/player/PlayerNotificationService.kt b/android/app/src/main/java/com/audiobookshelf/app/player/PlayerNotificationService.kt
index a967345b..ab6d5c60 100644
--- a/android/app/src/main/java/com/audiobookshelf/app/player/PlayerNotificationService.kt
+++ b/android/app/src/main/java/com/audiobookshelf/app/player/PlayerNotificationService.kt
@@ -732,32 +732,21 @@ class PlayerNotificationService : MediaBrowserServiceCompat() {
   }
 
   private fun setMediaSessionToCastVolume() {
-    val currentVol = try { castPlayer?.getDeviceVolume() ?: 0 } catch (e: Exception) { 0 }
+    val currentVol = try { castPlayer?.getDeviceVolume() ?: 0 } catch (_: Exception) { 0 }
     val provider = object : VolumeProviderCompat(VolumeProviderCompat.VOLUME_CONTROL_ABSOLUTE, 100, currentVol) {
       override fun onSetVolumeTo(volume: Int) {
+        // Clamp, update UI immediately, then send to device
         val clamped = volume.coerceIn(0, 100)
-        try {
-          castPlayer?.setDeviceVolume(clamped)
-          val actual = castPlayer?.getDeviceVolume() ?: clamped
-          setCurrentVolume(actual)
-        } catch (_: Exception) {}
+        setCurrentVolume(clamped)
+        try { castPlayer?.setDeviceVolume(clamped) } catch (_: Exception) {}
       }
+
       override fun onAdjustVolume(direction: Int) {
-        val current = try { castPlayer?.getDeviceVolume() ?: currentVolume } catch (_: Exception) { currentVolume }
-        val step = if (direction > 0) 1 else if (direction < 0) -1 else 0
-        if (step == 0) return
-        var target = (current + step).coerceIn(0, 100)
-        try {
-          castPlayer?.setDeviceVolume(target)
-          var actual = castPlayer?.getDeviceVolume() ?: current
-          // If device ignored tiny step, try nudging up to 3 steps total.
-          if (actual == current) {
-            target = (current + step * 3).coerceIn(0, 100)
-            castPlayer?.setDeviceVolume(target)
-            actual = castPlayer?.getDeviceVolume() ?: current
-          }
-          setCurrentVolume(actual)
-        } catch (_: Exception) {}
+        // Use Android-provided step (−1, 0, +1). Clamp, update UI immediately, then send.
+        val current = currentVolume
+        val target = (current + direction).coerceIn(0, 100)
+        setCurrentVolume(target)
+        try { castPlayer?.setDeviceVolume(target) } catch (_: Exception) {}
       }
     }
     remoteVolumeProvider = provider