Move the output device menu items to the main menu.

I don't know why I put them in the Preferences menu initially. This is
more convenient.

Closes #170.

Also:
 - Update the output device menu items as needed instead of when the
   user opens the menu. This saves a bit of CPU time and means if the
   user has the menu open, changes are made when they're needed instead
   of the next time the user opens the menu.
 - Fix BGMAppUITests::testCycleOutputDevices for the latest Xcode/macOS.

BGMApp/BGMApp.xcodeproj/project.pbxproj

@@ -300,8 +300,8 @@
 		1CD1FD2F1BDDEAF2004F7E1B /* AudioToolbox.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = AudioToolbox.framework; path = System/Library/Frameworks/AudioToolbox.framework; sourceTree = SDKROOT; };
 		1CD410D21F9EDDAD0070A094 /* BGMAppVolumesController.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = BGMAppVolumesController.h; sourceTree = "<group>"; };
 		1CD410D31F9EDDAD0070A094 /* BGMAppVolumesController.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = BGMAppVolumesController.mm; sourceTree = "<group>"; };
-		1CE7064A1BF1EC0600BFC06D /* BGMOutputDevicePrefs.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = BGMOutputDevicePrefs.h; path = Preferences/BGMOutputDevicePrefs.h; sourceTree = "<group>"; };
+		1CE7064A1BF1EC0600BFC06D /* BGMOutputDevicePrefs.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BGMOutputDevicePrefs.h; sourceTree = "<group>"; };
-		1CE7064B1BF1EC0600BFC06D /* BGMOutputDevicePrefs.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = BGMOutputDevicePrefs.mm; path = Preferences/BGMOutputDevicePrefs.mm; sourceTree = "<group>"; };
+		1CE7064B1BF1EC0600BFC06D /* BGMOutputDevicePrefs.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = BGMOutputDevicePrefs.mm; sourceTree = "<group>"; };
 		1CEACF4E1F34A30000FEC143 /* Mock_CAHALAudioSystemObject.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Mock_CAHALAudioSystemObject.cpp; path = UnitTests/Mock_CAHALAudioSystemObject.cpp; sourceTree = "<group>"; };
 		1CED61681C3081C2002CAFCF /* LICENSE */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = LICENSE; sourceTree = "<group>"; };
 		1CED616A1C316E1A002CAFCF /* BGMAudioDeviceManager.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BGMAudioDeviceManager.h; sourceTree = "<group>"; };
@@ -419,8 +419,6 @@
 				27D1D6BA1DD7226C0049E707 /* BGMAboutPanel.m */,
 				1C0BD0A31BF1A8E6004F4CF5 /* BGMAutoPauseMusicPrefs.h */,
 				1C0BD0A41BF1A8E6004F4CF5 /* BGMAutoPauseMusicPrefs.mm */,
-				1CE7064A1BF1EC0600BFC06D /* BGMOutputDevicePrefs.h */,
-				1CE7064B1BF1EC0600BFC06D /* BGMOutputDevicePrefs.mm */,
 			);
 			name = "Preferences Menu";
 			sourceTree = "<group>";
@@ -573,6 +571,8 @@
 				1C1465B71BCC3A73003AEFE6 /* BGMAutoPauseMusic.mm */,
 				1C4699451BD5BF2E00F78043 /* Music Players */,
 				1C0BD0A21BF1A827004F4CF5 /* Preferences Menu */,
+				1CE7064A1BF1EC0600BFC06D /* BGMOutputDevicePrefs.h */,
+				1CE7064B1BF1EC0600BFC06D /* BGMOutputDevicePrefs.mm */,
 				1C46994D1BD7694C00F78043 /* BGMDeviceControlSync.h */,
 				1C46994C1BD7694C00F78043 /* BGMDeviceControlSync.cpp */,
 				1C3D36711ED90E8600F98E66 /* BGMDeviceControlsList.h */,

BGMApp/BGMApp/BGMAppDelegate.mm

@@ -25,17 +25,18 @@
 
 // Local Includes
 #import "BGM_Utils.h"
-#import "BGMUserDefaults.h"
+#import "BGMAppVolumesController.h"
-#import "BGMMusicPlayers.h"
 #import "BGMAutoPauseMusic.h"
 #import "BGMAutoPauseMenuItem.h"
-#import "BGMSystemSoundsVolume.h"
+#import "BGMMusicPlayers.h"
-#import "BGMAppVolumesController.h"
+#import "BGMOutputDevicePrefs.h"
+#import "BGMOutputVolumeMenuItem.h"
 #import "BGMPreferencesMenu.h"
 #import "BGMPreferredOutputDevices.h"
-#import "BGMXPCListener.h"
+#import "BGMSystemSoundsVolume.h"
-#import "BGMOutputVolumeMenuItem.h"
 #import "BGMTermination.h"
+#import "BGMUserDefaults.h"
+#import "BGMXPCListener.h"
 #import "SystemPreferences.h"
 
 // System Includes
@@ -61,6 +62,7 @@ static NSString* const kOptShowDockIcon      = @"--show-dock-icon";
     BGMMusicPlayers* musicPlayers;
     BGMSystemSoundsVolume* systemSoundsVolume;
     BGMAppVolumesController* appVolumes;
+    BGMOutputDevicePrefs* outputDevicePrefs;
     BGMPreferencesMenu* prefsMenu;
     BGMXPCListener* xpcListener;
     BGMPreferredOutputDevices* preferredOutputDevices;
@@ -292,9 +294,15 @@ static NSString* const kOptShowDockIcon      = @"--show-dock-icon";
 
     [self initVolumesMenuSection];
 
+    // Output device selection.
+    outputDevicePrefs = [[BGMOutputDevicePrefs alloc] initWithBGMMenu:self.bgmMenu
+                                                         audioDevices:audioDevices
+                                                     preferredDevices:preferredOutputDevices];
+    [audioDevices setOutputDevicePrefs:outputDevicePrefs];
+
+    // Preferences submenu.
     prefsMenu = [[BGMPreferencesMenu alloc] initWithBGMMenu:self.bgmMenu
                                                audioDevices:audioDevices
-                                           preferredDevices:preferredOutputDevices
                                                musicPlayers:musicPlayers
                                                  aboutPanel:self.aboutPanel
                                       aboutPanelLicenseView:self.aboutPanelLicenseView];

BGMApp/BGMApp/BGMAudioDeviceManager.h

@@ -39,6 +39,7 @@
 
 // Forward Declarations
 @class BGMOutputVolumeMenuItem;
+@class BGMOutputDevicePrefs;
 
 
 #pragma clang assume_nonnull begin
@@ -54,6 +55,9 @@ static const int kBGMErrorCode_ReturningEarly       = 2;
 // Set the BGMOutputVolumeMenuItem to be notified when the output device is changed.
 - (void) setOutputVolumeMenuItem:(BGMOutputVolumeMenuItem*)item;
 
+// Set the BGMOutputDevicePrefs to be notified when the output device is changed.
+- (void) setOutputDevicePrefs:(BGMOutputDevicePrefs*)prefs;
+
 // Set BGMDevice as the default audio device for all processes
 - (NSError* __nullable) setBGMDeviceAsOSDefault;
 // Replace BGMDevice as the default device with the output device

BGMApp/BGMApp/BGMAudioDeviceManager.mm

@@ -26,16 +26,17 @@
 // Local Includes
 #import "BGM_Types.h"
 #import "BGM_Utils.h"
-#import "BGMDeviceControlSync.h"
-#import "BGMPlayThrough.h"
 #import "BGMAudioDevice.h"
-#import "BGMXPCProtocols.h"
+#import "BGMDeviceControlSync.h"
+#import "BGMOutputDevicePrefs.h"
 #import "BGMOutputVolumeMenuItem.h"
+#import "BGMPlayThrough.h"
+#import "BGMXPCProtocols.h"
 
 // PublicUtility Includes
-#import "CAHALAudioSystemObject.h"
-#import "CAAutoDisposer.h"
 #import "CAAtomic.h"
+#import "CAAutoDisposer.h"
+#import "CAHALAudioSystemObject.h"
 
 
 #pragma clang assume_nonnull begin
@@ -60,6 +61,7 @@
     NSXPCConnection* __nullable bgmXPCHelperConnection;
 
     BGMOutputVolumeMenuItem* __nullable outputVolumeMenuItem;
+    BGMOutputDevicePrefs* __nullable outputDevicePrefs;
 
     NSRecursiveLock* stateLock;
 }
@@ -71,6 +73,7 @@
         stateLock = [NSRecursiveLock new];
         bgmXPCHelperConnection = nil;
         outputVolumeMenuItem = nil;
+        outputDevicePrefs = nil;
         outputDevice = kAudioObjectUnknown;
 
         try {
@@ -102,6 +105,10 @@
     outputVolumeMenuItem = item;
 }
 
+- (void) setOutputDevicePrefs:(BGMOutputDevicePrefs*)prefs {
+    outputDevicePrefs = prefs;
+}
+
 #pragma mark Systemwide Default Device
 
 // Note that there are two different "default" output devices on OS X: "output" and "system output". See
@@ -324,6 +331,7 @@
 
     // Update the menu item for the volume of the output device.
     [outputVolumeMenuItem outputDeviceDidChange];
+    [outputDevicePrefs outputDeviceDidChange];
 }
 
 - (NSError*) failedToSetOutputDevice:(AudioDeviceID)deviceID

BGMApp/BGMApp/BGMOutputDevicePrefs.h

@@ -32,9 +32,13 @@
 
 @interface BGMOutputDevicePrefs : NSObject
 
-- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices
+- (instancetype) initWithBGMMenu:(NSMenu*)inBGMMenu
+                    audioDevices:(BGMAudioDeviceManager*)inAudioDevices
                 preferredDevices:(BGMPreferredOutputDevices*)inPreferredDevices;
-- (void) populatePreferencesMenu:(NSMenu*)prefsMenu;
+
+// To be called when BGMApp has been set to use a different output device. For example, when a new
+// device is connected and BGMPreferredOutputDevices decides BGMApp should switch to it.
+- (void) outputDeviceDidChange;
 
 @end
 

BGMApp/BGMApp/BGMOutputDevicePrefs.mm

@@ -29,36 +29,111 @@
 #import "BGMAudioDevice.h"
 
 // PublicUtility Includes
-#include "CAHALAudioSystemObject.h"
+#import "CAAutoDisposer.h"
-#include "CAHALAudioDevice.h"
+#import "CAHALAudioDevice.h"
-#include "CAAutoDisposer.h"
+#import "CAHALAudioSystemObject.h"
+#import "CAPropertyAddress.h"
+
+// STL Includes
+#import <set>
 
 
 #pragma clang assume_nonnull begin
 
-static NSInteger const kOutputDeviceMenuItemTag = 2;
+static NSInteger const kOutputDeviceMenuItemTag = 5;
 
 @implementation BGMOutputDevicePrefs {
+    NSMenu* bgmMenu;
     BGMAudioDeviceManager* audioDevices;
     BGMPreferredOutputDevices* preferredDevices;
     NSMutableArray<NSMenuItem*>* outputDeviceMenuItems;
+    // Called when a CoreAudio property has changed and we might need to update the menu. For
+    // example, when a device is connected or disconnected.
+    AudioObjectPropertyListenerBlock refreshNeededListener;
+    // The devices we've added refreshNeededListener to. Used to avoid adding it to a device twice
+    // for the same property and to remove it from all devices in dealloc.
+    std::set<BGMAudioDevice> listenedDevices_kAudioDevicePropertyDataSources;
+    std::set<BGMAudioDevice> listenedDevices_kAudioDevicePropertyDataSource;
 }
 
-- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices
+- (instancetype) initWithBGMMenu:(NSMenu*)inBGMMenu
+                    audioDevices:(BGMAudioDeviceManager*)inAudioDevices
                 preferredDevices:(BGMPreferredOutputDevices*)inPreferredDevices {
     if ((self = [super init])) {
+        bgmMenu = inBGMMenu;
         audioDevices = inAudioDevices;
         preferredDevices = inPreferredDevices;
         outputDeviceMenuItems = [NSMutableArray new];
+
+        [self listenForDevicesAddedOrRemoved];
+        [self populateBGMMenu];
     }
     
     return self;
 }
 
-- (void) populatePreferencesMenu:(NSMenu*)prefsMenu {
+- (void) dealloc {
+    // Tell CoreAudio not to call the listener block anymore. This probably isn't necessary.
+    //
+    // I think it's safe to do this without dispatching to the main queue because dealloc and
+    // refreshNeededListener should be essentially mutually exclusive. If refreshNeededListener is
+    // invoked and gets a value for weakSelf, it holds the strong ref until it returns, so dealloc
+    // won't be called. If refreshNeededListener is invoked and deallocation has started, it will
+    // get nil for weakSelf and just return.
+    auto removeListener = [&] (CAHALAudioObject audioObject, AudioObjectPropertySelector prop) {
+        BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+            // Check the object still exists first to reduce unnecessary error logs.
+            if (CAHALAudioObject::ObjectExists(audioObject.GetObjectID())) {
+                audioObject.RemovePropertyListenerBlock(CAPropertyAddress(prop),
+                                                        dispatch_get_main_queue(),
+                                                        refreshNeededListener);
+            }
+        });
+    };
+
+    // Remove the listener from each audio object we added it to.
+    removeListener(CAHALAudioSystemObject(), kAudioHardwarePropertyDevices);
+
+    for (auto device : listenedDevices_kAudioDevicePropertyDataSources) {
+        removeListener(device, kAudioDevicePropertyDataSources);
+    }
+
+    for (auto device : listenedDevices_kAudioDevicePropertyDataSource) {
+        removeListener(device, kAudioDevicePropertyDataSource);
+    }
+}
+
+- (void) listenForDevicesAddedOrRemoved {
+    // Create the block that will run when a device is added or removed.
+    BGMOutputDevicePrefs* __weak weakSelf = self;
+
+    refreshNeededListener = ^(UInt32 inNumberAddresses,
+                              const AudioObjectPropertyAddress* inAddresses) {
+        #pragma unused (inNumberAddresses, inAddresses)
+
+        BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+            [weakSelf populateBGMMenu];
+        });
+    };
+
+    // Register the listener block to be called when devices are connected or disconnected.
+    BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+        CAHALAudioSystemObject().AddPropertyListenerBlock(
+            CAPropertyAddress(kAudioHardwarePropertyDevices),
+            dispatch_get_main_queue(),
+            refreshNeededListener);
+    });
+}
+
+- (void) populateBGMMenu {
+    // TODO: Technically, we should assert we're on the main queue rather than just the main thread.
+    BGMAssert([NSThread isMainThread],
+              "BGMOutputDevicePrefs::populateBGMMenu called on non-main thread");
+
     // Remove existing menu items
     for (NSMenuItem* item in outputDeviceMenuItems) {
-        [prefsMenu removeItem:item];
+        DebugMsg("BGMOutputDevicePrefs::populateBGMMenu: Removing %s", item.description.UTF8String);
+        [bgmMenu removeItem:item];
     }
     
     [outputDeviceMenuItems removeAllObjects];
@@ -72,25 +147,51 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
         audioSystem.GetAudioDevices(numDevices, devices);
         
         for (UInt32 i = 0; i < numDevices; i++) {
-            [self insertMenuItemsForDevice:devices[i] preferencesMenu:prefsMenu];
+            [self insertMenuItemsForDevice:devices[i]];
         }
     }
 }
 
-- (void) insertMenuItemsForDevice:(BGMAudioDevice)device preferencesMenu:(NSMenu*)prefsMenu {
+- (void) insertMenuItemsForDevice:(BGMAudioDevice)device {
     // Insert menu items after the item for the "Output Device" heading.
-    const NSInteger menuItemsIdx = [prefsMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
+    const NSInteger menuItemsIdx = [bgmMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
 
     BOOL canBeOutputDevice = YES;
-    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::insertMenuItemsForDevice", ([&] {
+    BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
         canBeOutputDevice = device.CanBeOutputDeviceInBGMApp();
-    }));
+    });
 
     if (canBeOutputDevice) {
         for (NSMenuItem* item : [self createMenuItemsForDevice:device]) {
-            [prefsMenu insertItem:item atIndex:menuItemsIdx];
+            DebugMsg("BGMOutputDevicePrefs::insertMenuItemsForDevice: Inserting %s",
+                     item.description.UTF8String);
+            [bgmMenu insertItem:item atIndex:menuItemsIdx];
             [outputDeviceMenuItems addObject:item];
         }
+
+        // Add listeners to update the menu when the device's data source changes or it changes its
+        // list of data sources. We do this so that, for example, when you plug headphones into the
+        // built-in jack, the menu item for the built-in device will change from "Internal Speakers"
+        // to "Headphones".
+        if (listenedDevices_kAudioDevicePropertyDataSources.count(device) == 0) {
+            BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+                device.AddPropertyListenerBlock(CAPropertyAddress(kAudioDevicePropertyDataSources,
+                                                                  kAudioDevicePropertyScopeOutput),
+                                                dispatch_get_main_queue(),
+                                                refreshNeededListener);
+                listenedDevices_kAudioDevicePropertyDataSources.insert(device);
+            });
+        };
+
+        if (listenedDevices_kAudioDevicePropertyDataSource.count(device) == 0) {
+            BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+                device.AddPropertyListenerBlock(CAPropertyAddress(kAudioDevicePropertyDataSource,
+                                                                  kAudioDevicePropertyScopeOutput),
+                                                dispatch_get_main_queue(),
+                                                refreshNeededListener);
+                listenedDevices_kAudioDevicePropertyDataSource.insert(device);
+            });
+        };
     }
 }
 
@@ -110,7 +211,7 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
     // TODO: Use the current data source's name when the control isn't settable, but only add one menu item.
     UInt32 numDataSources = 0;
 
-    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemsForDevice", [&] {
+    BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
         if (device.HasDataSourceControl(scope, channel) &&
                 device.DataSourceControlIsSettable(scope, channel)) {
             numDataSources = device.GetNumberAvailableDataSources(scope, channel);
@@ -127,14 +228,13 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
                      "Device ID:", device.GetObjectID(),
                      ", Data source ID:", dataSourceIDs[i]);
 
-            BGMLogAndSwallowExceptionsMsg("BGMOutputDevicePrefs::createMenuItemsForDevice", "(DS)", [&]() {
+            BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, "(DS)", [&] {
-                NSNumber* dataSourceID = [NSNumber numberWithUnsignedInt:dataSourceIDs[i]];
                 NSString* dataSourceName =
                     CFBridgingRelease(device.CopyDataSourceNameForID(scope, channel, dataSourceIDs[i]));
                 NSString* deviceName = CFBridgingRelease(device.CopyName());
                 
                 [items addObject:[self createMenuItemForDevice:device
-                                                  dataSourceID:dataSourceID
+                                                  dataSourceID:@(dataSourceIDs[i])
                                                          title:dataSourceName
                                                        toolTip:deviceName]];
             });
@@ -143,12 +243,12 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
         DebugMsg("BGMOutputDevicePrefs::createMenuItemsForDevice: Creating item. %s%u",
                  "Device ID:", device.GetObjectID());
 
-        BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemsForDevice", ([&] {
+        BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
             [items addObject:[self createMenuItemForDevice:device
                                               dataSourceID:nil
                                                      title:CFBridgingRelease(device.CopyName())
                                                    toolTip:nil]];
-        }));
+        });
     }
     
     return items;
@@ -164,13 +264,13 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
     }
     
     NSMenuItem* item = [[NSMenuItem alloc] initWithTitle:BGMNN(title)
-                                                  action:@selector(outputDeviceWasChanged:)
+                                                  action:@selector(outputDeviceMenuItemSelected:)
                                            keyEquivalent:@""];
     
     // Add the AirPlay icon to the labels of AirPlay devices.
     //
     // TODO: Test this with real hardware that supports AirPlay. (I don't have any.)
-    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemForDevice", [&] {
+    BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
         if (device.GetTransportType() == kAudioDeviceTransportTypeAirPlay) {
             item.image = [NSImage imageNamed:@"AirPlayIcon"];
             
@@ -193,11 +293,27 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
     item.representedObject = @{ @"deviceID": @(device.GetObjectID()),
                                 @"dataSourceID": dataSourceID ? BGMNN(dataSourceID) : [NSNull null] };
 
+    if (@available(macOS 10.10, *)) {
+        // Used for UI tests.
+        item.accessibilityIdentifier = @"output-device";
+    }
+    
     return item;
 }
 
-- (void) outputDeviceWasChanged:(NSMenuItem*)menuItem {
+// Called by BGMAudioDeviceManager to tell us a different device has been set as the output device.
-    DebugMsg("BGMOutputDevicePrefs::outputDeviceWasChanged: '%s' menu item selected",
+- (void) outputDeviceDidChange {
+    BGMOutputDevicePrefs* __weak weakSelf = self;
+
+    dispatch_async(dispatch_get_main_queue(), ^{
+        BGM_Utils::LogAndSwallowExceptions(BGMDbgArgs, [&] {
+            [weakSelf populateBGMMenu];
+        });
+    });
+}
+
+- (void) outputDeviceMenuItemSelected:(NSMenuItem*)menuItem {
+    DebugMsg("BGMOutputDevicePrefs::outputDeviceMenuItemSelected: '%s' menu item selected",
              [menuItem.title UTF8String]);
     
     // Make sure the menu item is actually for an output device.
@@ -220,14 +336,14 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
                 [NSString stringWithFormat:@"%@ (%@)", menuItem.title, menuItem.toolTip] :
                 menuItem.title;
 
-        // Dispatched because it usually blocks. (Note that we're using
-        // DISPATCH_QUEUE_PRIORITY_HIGH, which is the second highest priority.)
-        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
         if (changingDevice) {
             // Add the new output device to the list of preferred devices.
             [preferredDevices userChangedOutputDeviceTo:newDeviceID];
         }
 
+        // Dispatched because it usually blocks. (Note that we're using
+        // DISPATCH_QUEUE_PRIORITY_HIGH, which is the second highest priority.)
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
             [self changeToOutputDevice:newDeviceID
                          newDataSource:newDataSourceID
                             deviceName:deviceName];

BGMApp/BGMApp/BGMOutputVolumeMenuItem.mm

@@ -210,6 +210,14 @@ NSString* const __nonnull      kGenericOutputDeviceName = @"Output Device";
 - (void) removeOutputDeviceDataSourceListener {
     BGMLogAndSwallowExceptions("BGMOutputVolumeMenuItem::removeOutputDeviceDataSourceListener",
                                ([&] {
+        // Technically, there's a race here in that the device could be removed after we check it
+        // exists, but before we try to remove the listener. We could check the error code of the
+        // exception and not log an error message if the code is kAudioHardwareBadObjectError or
+        // kAudioHardwareBadDeviceError, but it probably wouldn't be worth the effort.
+        //
+        // So for now the main reason for checking the device exists here is that it makes debug
+        // builds much less likely to crash here. (They crash/break when an error is logged so it
+        // will be noticed.)
         if (CAHALAudioObject::ObjectExists(outputDevice)) {
             outputDevice.RemovePropertyListenerBlock(
                 CAPropertyAddress(kAudioDevicePropertyDataSource, kScope),

BGMApp/BGMApp/Base.lproj/MainMenu.xib

@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14313.18" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
     <dependencies>
         <deployment identifier="macosx"/>
         <development version="8000" identifier="xcode"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14313.18"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14460.31"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <objects>
@@ -40,6 +40,10 @@
                     <modifierMask key="keyEquivalentModifierMask"/>
                 </menuItem>
                 <menuItem isSeparatorItem="YES" tag="4" id="rkf-nx-H2J"/>
+                <menuItem title="Output Device" tag="5" enabled="NO" id="chk-9C-pab">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                </menuItem>
+                <menuItem isSeparatorItem="YES" id="D3z-zv-JrJ"/>
                 <menuItem title="Preferences" tag="1" id="BHb-uh-9Zm">
                     <modifierMask key="keyEquivalentModifierMask"/>
                     <menu key="submenu" title="Preferences" id="Img-Dh-cpU">
@@ -48,10 +52,6 @@
                                 <modifierMask key="keyEquivalentModifierMask"/>
                             </menuItem>
                             <menuItem isSeparatorItem="YES" id="nb1-jq-97L"/>
-                            <menuItem title="Output Device" tag="2" enabled="NO" id="chk-9C-pab">
-                                <modifierMask key="keyEquivalentModifierMask"/>
-                            </menuItem>
-                            <menuItem isSeparatorItem="YES" id="D3z-zv-JrJ"/>
                             <menuItem title="About Background Music" tag="3" id="R45-Vo-Eto">
                                 <modifierMask key="keyEquivalentModifierMask"/>
                             </menuItem>

BGMApp/BGMApp/Preferences/BGMPreferencesMenu.h

@@ -25,7 +25,6 @@
 
 // Local Includes
 #import "BGMAudioDeviceManager.h"
-#import "BGMPreferredOutputDevices.h"
 #import "BGMMusicPlayers.h"
 
 // System Includes
@@ -34,11 +33,10 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@interface BGMPreferencesMenu : NSObject <NSMenuDelegate>
+@interface BGMPreferencesMenu : NSObject
 
 - (id) initWithBGMMenu:(NSMenu*)inBGMMenu
           audioDevices:(BGMAudioDeviceManager*)inAudioDevices
-      preferredDevices:(BGMPreferredOutputDevices*)inPreferredDevices
           musicPlayers:(BGMMusicPlayers*)inMusicPlayers
             aboutPanel:(NSPanel*)inAboutPanel
  aboutPanelLicenseView:(NSTextView*)inAboutPanelLicenseView;

BGMApp/BGMApp/Preferences/BGMPreferencesMenu.mm

@@ -25,7 +25,6 @@
 
 // Local Includes
 #import "BGMAutoPauseMusicPrefs.h"
-#import "BGMOutputDevicePrefs.h"
 #import "BGMAboutPanel.h"
 
 
@@ -38,7 +37,6 @@ static NSInteger const kAboutPanelMenuItemTag = 3;
 @implementation BGMPreferencesMenu {
     // Menu sections
     BGMAutoPauseMusicPrefs* autoPauseMusicPrefs;
-    BGMOutputDevicePrefs* outputDevicePrefs;
     
     // The About Background Music window
     BGMAboutPanel* aboutPanel;
@@ -46,21 +44,16 @@ static NSInteger const kAboutPanelMenuItemTag = 3;
 
 - (id) initWithBGMMenu:(NSMenu*)inBGMMenu
           audioDevices:(BGMAudioDeviceManager*)inAudioDevices
-      preferredDevices:(BGMPreferredOutputDevices*)inPreferredDevices
           musicPlayers:(BGMMusicPlayers*)inMusicPlayers
             aboutPanel:(NSPanel*)inAboutPanel
  aboutPanelLicenseView:(NSTextView*)inAboutPanelLicenseView {
     if ((self = [super init])) {
         NSMenu* prefsMenu = [[inBGMMenu itemWithTag:kPreferencesMenuItemTag] submenu];
-        [prefsMenu setDelegate:self];
         
         autoPauseMusicPrefs = [[BGMAutoPauseMusicPrefs alloc] initWithPreferencesMenu:prefsMenu
                                                                          audioDevices:inAudioDevices
                                                                          musicPlayers:inMusicPlayers];
         
-        outputDevicePrefs = [[BGMOutputDevicePrefs alloc] initWithAudioDevices:inAudioDevices
-                                                              preferredDevices:inPreferredDevices];
-        
         aboutPanel = [[BGMAboutPanel alloc] initWithPanel:inAboutPanel licenseView:inAboutPanelLicenseView];
         
         // Set up the "About Background Music" menu item
@@ -72,12 +65,6 @@ static NSInteger const kAboutPanelMenuItemTag = 3;
     return self;
 }
 
-#pragma mark NSMenuDelegate
-
-- (void) menuNeedsUpdate:(NSMenu*)menu {
-    [outputDevicePrefs populatePreferencesMenu:menu];
-}
-
 @end
 
 NS_ASSUME_NONNULL_END

BGMApp/BGMAppTests/UITests/BGMApp.h

@@ -1,5 +1,8 @@
 /*
  * BGMApp.h
+ *
+ * Generated with
+ * sdef "/Applications/Background Music.app" | sdp -fh --basename BGMApp
  */
 
 #import <AppKit/AppKit.h>
@@ -14,11 +17,11 @@
  * Background Music
  */
 
-// an output audio device
+// A hardware device that can play audio
 @interface BGMAppOutputDevice : SBObject
 
-@property (copy, readonly) NSString *name;
+@property (copy, readonly) NSString *name;  // The name of the output device.
-@property BOOL selected;  // is this the device to be used for audio output?
+@property BOOL selected;  // Is this the device to be used for audio output?
 
 @end
 
@@ -27,5 +30,7 @@
 
 - (SBElementArray<BGMAppOutputDevice *> *) outputDevices;
 
+@property (copy) BGMAppOutputDevice *selectedOutputDevice;  // The device to be used for audio output
+
 @end
 

BGMApp/BGMAppTests/UITests/BGMAppUITests.mm

@@ -17,7 +17,7 @@
 //  BGMAppUITests.mm
 //  BGMAppUITests
 //
-//  Copyright © 2017 Kyle Neideck
+//  Copyright © 2017, 2018 Kyle Neideck
 //
 //  You might want to use Xcode's UI test recording feature if you add new tests.
 //
@@ -60,8 +60,8 @@
     // Set up the app object and some convenience vars.
     app = [[XCUIApplication alloc] init];
     menuItems = app.menuBars.menuItems;
-    icon = [app.menuBars childrenMatchingType:XCUIElementTypeMenuBarItem].element;
     prefs = menuItems[@"Preferences"];
+    icon = [app.menuBars childrenMatchingType:XCUIElementTypeStatusItem].element;
 
     // TODO: Make sure BGMDevice isn't set as the OS X default device before launching BGMApp.
 
@@ -72,6 +72,20 @@
 
     // Launch BGMApp.
     [app launch];
+
+     if (![icon waitForExistenceWithTimeout:1.0]) {
+        // The status bar icon/button has this type when using older versions of XCTest, so try
+        // both. (Actually, it might depend on the macOS or Xcode version. I'm not sure.)
+        XCUIElement* iconOldType =
+                [app.menuBars childrenMatchingType:XCUIElementTypeMenuBarItem].element;
+         if (![iconOldType waitForExistenceWithTimeout:5.0]) {
+             icon = iconOldType;
+         }
+    }
+
+    // Wait for the initial elements.
+    XCTAssert([app waitForExistenceWithTimeout:10.0]);
+    XCTAssert([icon waitForExistenceWithTimeout:10.0]);
 }
 
 - (void) tearDown {
@@ -91,10 +105,22 @@
 - (void) testCycleOutputDevices {
     const int NUM_CYCLES = 2;
 
-    // Get the list of output devices from the preferences menu.
+    // sbApp lets us use AppleScript to query BGMApp and check the test has made the changes to its
+    // settings we expect.
+    BGMAppApplication* sbApp = [SBApplication applicationWithBundleIdentifier:@kBGMAppBundleID];
+
+    // Get macOS to show the "'Xcode' wants to control 'Background Music'" dialog before we start
+    // the test so it doesn't interrupt it.
+    [[sbApp selectedOutputDevice] name];
+
+    // Click the icon to open the main menu.
     [icon click];
-    [prefs hover];
+
-    NSArray<XCUIElement*>* outputDeviceMenuItems = [self outputDeviceMenuItems];
+    // Get the list of output devices from the main menu.
+    // BGMOutputDevicePrefs::createMenuItemForDevice gives every output device menu item the
+    // accessibility identifier "output-device" so we can find all of them here.
+    NSArray<XCUIElement*>* outputDeviceMenuItems =
+        [menuItems matchingIdentifier:@"output-device"].allElementsBoundByIndex;
 
     // For debugging certain issues, it can be useful to repeatedly switch between two
     // devices:
@@ -105,14 +131,10 @@
     // Click the last device to close the menu again.
     [outputDeviceMenuItems.lastObject click];
 
-    BGMAppApplication* sbApp = [SBApplication applicationWithBundleIdentifier:@kBGMAppBundleID];
-
     for (int i = 0; i < NUM_CYCLES; i++) {
         // Select each output device.
         for (XCUIElement* item in outputDeviceMenuItems) {
             [icon click];
-            [prefs hover];
-
             [item click];
 
             // Assert that the device we clicked is the selected device now.
@@ -128,29 +150,6 @@
     }
 }
 
-// Find the menu items for the output devices in the preferences menu.
-- (NSArray<XCUIElement*>*) outputDeviceMenuItems {
-    NSArray<XCUIElement*>* items = @[];
-    BOOL inOutputDeviceSection = NO;
-
-    for (int i = 0; i < prefs.menuItems.count; i++) {
-        XCUIElement* menuItem = [prefs.menuItems elementBoundByIndex:i];
-
-        if ([menuItem.title isEqual:@"Output Device"]) {
-            inOutputDeviceSection = YES;
-        } else if (inOutputDeviceSection) {
-            // Assume that finding a separator menu item means we've reached the end of the section.
-            if (((NSMenuItem*)menuItem.value).separatorItem || [menuItem.title isEqual:@""]) {
-                break;
-            }
-
-            items = [items arrayByAddingObject:menuItem];
-        }
-    }
-
-    return items;
-}
-
 - (void) testSelectMusicPlayer {
     // Select VLC as the music player.
     [icon click];