Add sound split disabled mode (#16331)

Closes #16287

Summary of the issue:
Disabling sound split still could touch channel volumes.

Description of development approach
1. If sound split mode is disabled at startup, we're not touching any volumes.
2. If user toggles to disabled mode, then first we set mode to NVDA_BOTH_APPS_BOTH to effectively restore the volumes, then set sound pslit state to off.

source/audio/soundSplit.py

@@ -23,18 +23,25 @@
 @unique
 class SoundSplitState(DisplayStringIntEnum):
 	OFF = 0
-	NVDA_LEFT_APPS_RIGHT = 1
-	NVDA_LEFT_APPS_BOTH = 2
-	NVDA_RIGHT_APPS_LEFT = 3
-	NVDA_RIGHT_APPS_BOTH = 4
-	NVDA_BOTH_APPS_LEFT = 5
-	NVDA_BOTH_APPS_RIGHT = 6
+	NVDA_BOTH_APPS_BOTH = 1
+	NVDA_LEFT_APPS_RIGHT = 2
+	NVDA_LEFT_APPS_BOTH = 3
+	NVDA_RIGHT_APPS_LEFT = 4
+	NVDA_RIGHT_APPS_BOTH = 5
+	NVDA_BOTH_APPS_LEFT = 6
+	NVDA_BOTH_APPS_RIGHT = 7
+
 
 	@property
 	def _displayStringLabels(self) -> dict[IntEnum, str]:
 		return {
 			# Translators: Sound split state
-			SoundSplitState.OFF: pgettext("SoundSplit", "Disabled"),
+			SoundSplitState.OFF: pgettext("SoundSplit", "Sound split disabled"),
+			SoundSplitState.NVDA_BOTH_APPS_BOTH: pgettext(
+				"SoundSplit",
+				# Translators: Sound split state
+				"NVDA in both channels and applications in both channels",
+			),
 			# Translators: Sound split state
 			SoundSplitState.NVDA_LEFT_APPS_RIGHT: _("NVDA on the left and applications on the right"),
 			# Translators: Sound split state
@@ -51,7 +58,11 @@ def _displayStringLabels(self) -> dict[IntEnum, str]:
 
 	def getAppVolume(self) -> VolumeTupleT:
 		match self:
-			case SoundSplitState.OFF | SoundSplitState.NVDA_LEFT_APPS_BOTH | SoundSplitState.NVDA_RIGHT_APPS_BOTH:
+			case (
+				SoundSplitState.NVDA_BOTH_APPS_BOTH
+				| SoundSplitState.NVDA_LEFT_APPS_BOTH
+				| SoundSplitState.NVDA_RIGHT_APPS_BOTH
+			):
 				return (1.0, 1.0)
 			case SoundSplitState.NVDA_RIGHT_APPS_LEFT | SoundSplitState.NVDA_BOTH_APPS_LEFT:
 				return (1.0, 0.0)
@@ -62,7 +73,11 @@ def getAppVolume(self) -> VolumeTupleT:
 
 	def getNVDAVolume(self) -> VolumeTupleT:
 		match self:
-			case SoundSplitState.OFF | SoundSplitState.NVDA_BOTH_APPS_LEFT | SoundSplitState.NVDA_BOTH_APPS_RIGHT:
+			case (
+				SoundSplitState.NVDA_BOTH_APPS_BOTH
+				| SoundSplitState.NVDA_BOTH_APPS_LEFT
+				| SoundSplitState.NVDA_BOTH_APPS_RIGHT
+			):
 				return (1.0, 1.0)
 			case SoundSplitState.NVDA_LEFT_APPS_RIGHT | SoundSplitState.NVDA_LEFT_APPS_BOTH:
 				return (1.0, 0.0)
@@ -85,15 +100,17 @@ def initialize() -> None:
 			log.exception("Could not initialize audio session manager")
 			return
 		state = SoundSplitState(config.conf["audio"]["soundSplitState"])
-		setSoundSplitState(state)
+		setSoundSplitState(state, initial=True)
 	else:
 		log.debug("Cannot initialize sound split as WASAPI is disabled")
 
 
 @atexit.register
 def terminate():
 	if nvwave.usingWasapiWavePlayer():
-		setSoundSplitState(SoundSplitState.OFF)
+		state = SoundSplitState(config.conf["audio"]["soundSplitState"])
+		if state != SoundSplitState.OFF:
+			setSoundSplitState(SoundSplitState.OFF)
 		unregisterCallback()
 	else:
 		log.debug("Skipping terminating sound split as WASAPI is disabled.")
@@ -153,11 +170,20 @@ def on_session_created(self, new_session: AudioSession):
 			channelVolume.SetChannelVolume(1, self.rightNVDAVolume, None)
 
 
-def setSoundSplitState(state: SoundSplitState) -> dict:
+def setSoundSplitState(state: SoundSplitState, initial: bool = False) -> dict:
+	applyToFuture = True
+	if state == SoundSplitState.OFF:
+		if initial:
+			return {}
+		else:
+			# Disabling sound split via command or via settings
+			# We need to restore volume of all applications, but then don't set up callback for future audio sessions
+			state = SoundSplitState.NVDA_BOTH_APPS_BOTH
+			applyToFuture = False
 	leftVolume, rightVolume = state.getAppVolume()
 	leftNVDAVolume, rightNVDAVolume = state.getNVDAVolume()
 	volumeSetter = VolumeSetter(leftVolume, rightVolume, leftNVDAVolume, rightNVDAVolume)
-	applyToAllAudioSessions(volumeSetter)
+	applyToAllAudioSessions(volumeSetter, applyToFuture=applyToFuture)
 	return {
 		"foundSessionWithNot2Channels": volumeSetter.foundSessionWithNot2Channels,
 	}

source/config/configSpec.py

@@ -58,7 +58,7 @@
 	audioAwakeTime = integer(default=30, min=0, max=3600)
 	whiteNoiseVolume = integer(default=0, min=0, max=100)
 	soundSplitState = integer(default=0)
-	includedSoundSplitModes = int_list(default=list(0, 1, 2))
+	includedSoundSplitModes = int_list(default=list(0, 2, 3))
 
 # Braille settings
 [braille]