Use data source names instead of device names in the output device menu.

The names of the data source(s) for a device are generally the names intended to be shown to the user, since the OS X volume menu, System Preferences, etc. use them. A menu item is now added for each data source of each output device, rather than one per device. Also adds some macros/functions for casting values to __nonnull. Resolves #59.
2024-09-20 06:21:54 +00:00 · 2016-12-23 01:46:27 +11:00 · 2016-12-23 01:46:27 +11:00 · 7992a5708c
commit 7992a5708c
parent 31b501e832
13 changed files with 511 additions and 88 deletions
--- a/BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/BGMXPCHelper.xcscheme
+++ b/BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/BGMXPCHelper.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0810"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/Background
+++ b/BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/Background
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0810"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/BGMApp/BGMApp/AppDelegate.mm
+++ b/BGMApp/BGMApp/AppDelegate.mm
@ -36,6 +36,8 @@
 #import "SystemPreferences.h"


+#pragma clang assume_nonnull begin
+
 static float const kStatusBarIconPadding = 0.25;

@implementation AppDelegate {
@ -81,6 +83,15 @@ static float const kStatusBarIconPadding = 0.25;

 - (void) applicationDidFinishLaunching:(NSNotification*)aNotification {
    #pragma unused (aNotification)
+    
+    // Log the version/build number.
+    //
+    // TODO: NSLog should only be used for logging errors.
+    // TODO: Automatically add the commit ID to the end of the build number for unreleased builds. (In the
+    //       Info.plist or something -- not here.)
+    NSLog(@"BGMApp version: %@, BGMApp build number: %@",
+          NSBundle.mainBundle.infoDictionary[@"CFBundleShortVersionString"],
+          NSBundle.mainBundle.infoDictionary[@"CFBundleVersion"]);

    // Set up the rest of the UI and other external interfaces.
    
@ -140,8 +151,10 @@ static float const kStatusBarIconPadding = 0.25;
 }

 - (void) applicationWillTerminate:(NSNotification*)aNotification {
-#pragma unused (aNotification)
+    #pragma unused (aNotification)
    
+    DebugMsg("AppDelegate::applicationWillTerminate");
+
    NSError* error = [audioDevices unsetBGMDeviceAsOSDefault];
    
    if (error) {
@ -271,3 +284,5 @@ static float const kStatusBarIconPadding = 0.25;

@end

+#pragma clang assume_nonnull end
+
--- a/BGMApp/BGMApp/BGMAudioDeviceManager.h
+++ b/BGMApp/BGMApp/BGMAudioDeviceManager.h
@ -26,12 +26,12 @@

 // PublicUtility Includes
 #ifdef __cplusplus
-#include "CAHALAudioDevice.h"
+#import "CAHALAudioDevice.h"
 #endif

 // System Includes
 #import <Foundation/Foundation.h>
-#include <CoreAudio/AudioHardwareBase.h>
+#import <CoreAudio/AudioHardwareBase.h>


 #pragma clang assume_nonnull begin
@ -53,6 +53,8 @@ extern int const kBGMErrorCode_OutputDeviceNotFound;
 #endif

 - (BOOL) isOutputDevice:(AudioObjectID)deviceID;
+- (BOOL) isOutputDataSource:(UInt32)dataSourceID;
+
 // Set the audio output device that BGMApp uses.
 //
 // Returns an error if the output device couldn't be changed. If revertOnFailure is true in that case,
@ -61,9 +63,17 @@ extern int const kBGMErrorCode_OutputDeviceNotFound;
 //
 // Both errors' codes will be the code of the exception that caused the failure, if any, generally one
 // of the error constants from AudioHardwareBase.h.
+//
+// Blocks while the old device stops IO (if there was one).
 - (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
                              revertOnFailure:(BOOL)revertOnFailure;

+// As above, but also sets the new output device's data source. See kAudioDevicePropertyDataSource in
+// AudioHardware.h.
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                                 dataSourceID:(UInt32)dataSourceID
+                              revertOnFailure:(BOOL)revertOnFailure;
+
 // Blocks until IO has started running on the output device (for playthrough).
 - (OSStatus) waitForOutputDeviceToStart;

--- a/BGMApp/BGMApp/BGMAudioDeviceManager.mm
+++ b/BGMApp/BGMApp/BGMAudioDeviceManager.mm
@ -265,40 +265,90 @@ public:
    }
 }

- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID revertOnFailure:(BOOL)revertOnFailure {
-    DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting output device. deviceID=%u", deviceID);
+- (BOOL) isOutputDataSource:(UInt32)dataSourceID {
+    @synchronized (self) {
+        try {
+            AudioObjectPropertyScope scope = kAudioDevicePropertyScopeOutput;
+            UInt32 channel = 0;
+            
+            return outputDevice.HasDataSourceControl(scope, channel) &&
+                (dataSourceID == outputDevice.GetCurrentDataSourceID(scope, channel));
+        } catch (CAException e) {
+            BGMLogException(e);
+            return false;
+        }
+    }
+}
+
+
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                              revertOnFailure:(BOOL)revertOnFailure {
+    return [self setOutputDeviceWithIDImpl:deviceID
+                              dataSourceID:nil
+                           revertOnFailure:revertOnFailure];
+}
+
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                                 dataSourceID:(UInt32)dataSourceID
+                              revertOnFailure:(BOOL)revertOnFailure {
+    return [self setOutputDeviceWithIDImpl:deviceID
+                              dataSourceID:&dataSourceID
+                           revertOnFailure:revertOnFailure];
+}
+
+- (NSError* __nullable) setOutputDeviceWithIDImpl:(AudioObjectID)newDeviceID
+                                     dataSourceID:(UInt32* __nullable)dataSourceID
+                                  revertOnFailure:(BOOL)revertOnFailure {
+    DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting output device. newDeviceID=%u",
+             newDeviceID);
    
-    AudioDeviceID currentDeviceID = outputDevice.GetObjectID();
+    AudioDeviceID currentDeviceID = outputDevice.GetObjectID();  // (GetObjectID doesn't throw.)
    
    // Set up playthrough and control sync
-    BGMAudioDevice newOutputDevice(deviceID);
+    BGMAudioDevice newOutputDevice(newDeviceID);
    
    try {
        @synchronized (self) {
-            // Mirror changes in BGMDevice's controls to the new output device's.
-            deviceControlSync = BGMDeviceControlSync(bgmDevice, newOutputDevice);
+            // Re-read the device ID after entering the monitor. (The initial read is because
+            // currentDeviceID's used in the catch blocks.)
+            currentDeviceID = outputDevice.GetObjectID();
            
-            // Stream audio from BGMDevice to the output device.
-            //
-            // TODO: Should this be done async? Some output devices take a long time to start IO (e.g. AirPlay) and I
-            //       assume this blocks the main thread. Haven't tried it to check, though.
-            playThrough = BGMPlayThrough(bgmDevice, newOutputDevice);
+            if (newDeviceID != currentDeviceID) {
+                // Mirror changes in BGMDevice's controls to the new output device's.
+                deviceControlSync = BGMDeviceControlSync(bgmDevice, newOutputDevice);
+                
+                // Stream audio from BGMDevice to the new output device. This blocks while the old device
+                // stops IO.
+                playThrough = BGMPlayThrough(bgmDevice, newOutputDevice);

-            outputDevice = BGMAudioDevice(deviceID);
+                outputDevice = newOutputDevice;
+            }
+            
+            // Set the output device to use the new data source.
+            if (dataSourceID) {
+                // TODO: If this fails, ideally we'd still start playthrough and return an error, but not
+                //       revert the device. It would probably be a bit awkward, though.
+                [self setDataSource:*dataSourceID device:outputDevice];
+            }
+            
+            if (newDeviceID != currentDeviceID) {
+                // We successfully changed to the new device. Start playthrough on it, since audio might be
+                // playing. (If we only changed the data source, playthrough will already be running if it
+                // needs to be.)
+                playThrough.Start();
+                // But stop playthrough if audio isn't playing, since it uses CPU.
+                playThrough.StopIfIdle();
+            }
        }
-        
-        // Start playthrough because audio might be playing.
-        //
-        // TODO: If audio isn't playing, this makes playthrough run until the user plays audio and then stops it again,
-        //       which wastes CPU. I think we could just have Start() call StopIfIdle(), but I haven't tried it yet.
-        playThrough.Start();
-        playThrough.StopIfIdle();
    } catch (CAException e) {
-        return [self failedToSetOutputDevice:newOutputDevice.GetObjectID()
+        BGMAssert(e.GetError() != kAudioHardwareNoError,
+                  "CAException with kAudioHardwareNoError");
+        
+        return [self failedToSetOutputDevice:newDeviceID
                                   errorCode:e.GetError()
                                    revertTo:(revertOnFailure ? &currentDeviceID : nullptr)];
    } catch (...) {
-        return [self failedToSetOutputDevice:newOutputDevice.GetObjectID()
+        return [self failedToSetOutputDevice:newDeviceID
                                   errorCode:kAudioHardwareUnspecifiedError
                                    revertTo:(revertOnFailure ? &currentDeviceID : nullptr)];
    }
@ -306,6 +356,20 @@ public:
    return nil;
 }

+- (void) setDataSource:(UInt32)dataSourceID device:(BGMAudioDevice)device {
+    BGMLogAndSwallowExceptions("BGMAudioDeviceManager::setDataSource", [&]() {
+        AudioObjectPropertyScope scope = kAudioObjectPropertyScopeOutput;
+        UInt32 channel = 0;
+        
+        if (device.DataSourceControlIsSettable(scope, channel)) {
+            DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting dataSourceID=%u",
+                     dataSourceID);
+            
+            device.SetCurrentDataSourceByID(scope, channel, dataSourceID);
+        }
+    });
+}
+
 - (NSError*) failedToSetOutputDevice:(AudioDeviceID)deviceID
                           errorCode:(OSStatus)errorCode
                            revertTo:(AudioDeviceID*)revertTo {
--- a/BGMApp/BGMApp/Base.lproj/MainMenu.xib
+++ b/BGMApp/BGMApp/Base.lproj/MainMenu.xib
@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="11542" systemVersion="16B2333a" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="11542" systemVersion="16C48b" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
    <dependencies>
        <deployment identifier="macosx"/>
        <development version="7000" identifier="xcode"/>
@ -86,17 +86,17 @@
            </subviews>
            <point key="canvasLocation" x="81" y="-111"/>
        </customView>
-        <window allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" restorable="NO" hidesOnDeactivate="YES" oneShot="NO" releasedWhenClosed="NO" showsToolbarButton="NO" visibleAtLaunch="NO" animationBehavior="default" id="Cf4-3V-gl1" customClass="NSPanel">
+        <window allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" restorable="NO" hidesOnDeactivate="YES" oneShot="NO" showsToolbarButton="NO" visibleAtLaunch="NO" animationBehavior="default" id="Cf4-3V-gl1" customClass="NSPanel">
            <windowStyleMask key="styleMask" titled="YES" closable="YES" utility="YES"/>
            <windowPositionMask key="initialPositionMask" topStrut="YES"/>
-            <rect key="contentRect" x="248" y="350" width="816" height="310"/>
+            <rect key="contentRect" x="248" y="350" width="980" height="335"/>
            <rect key="screenRect" x="0.0" y="0.0" width="1280" height="778"/>
            <view key="contentView" id="HlB-hX-Y0Y">
-                <rect key="frame" x="0.0" y="0.0" width="816" height="310"/>
+                <rect key="frame" x="0.0" y="0.0" width="980" height="335"/>
                <autoresizingMask key="autoresizingMask"/>
                <subviews>
                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="r51-dd-LGP">
-                        <rect key="frame" x="53" y="95" width="240" height="22"/>
+                        <rect key="frame" x="61" y="125" width="240" height="22"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Background Music" id="Dw2-nu-eBQ">
                            <font key="font" size="18" name=".HelveticaNeueDeskInterface-Regular"/>
@ -105,7 +105,7 @@
                        </textFieldCell>
                    </textField>
                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="1" translatesAutoresizingMaskIntoConstraints="NO" id="ekc-h0-I43">
-                        <rect key="frame" x="53" y="70" width="240" height="17"/>
+                        <rect key="frame" x="61" y="100" width="240" height="17"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Version 0.1.0" id="FDH-7l-wFf">
                            <font key="font" metaFont="system"/>
@ -114,7 +114,7 @@
                        </textFieldCell>
                    </textField>
                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="L5P-Lw-aCd">
-                        <rect key="frame" x="367" y="273" width="270" height="17"/>
+                        <rect key="frame" x="391" y="298" width="270" height="17"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="left" title="Licensed under GPLv2 or any later version." id="ETh-En-bzX">
                            <font key="font" metaFont="system"/>
@ -123,11 +123,11 @@
                        </textFieldCell>
                    </textField>
                    <box horizontalHuggingPriority="750" fixedFrame="YES" boxType="separator" translatesAutoresizingMaskIntoConstraints="NO" id="Zc9-gs-X8C">
-                        <rect key="frame" x="332" y="88" width="5" height="150"/>
+                        <rect key="frame" x="361" y="93" width="5" height="150"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                    </box>
                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="2" translatesAutoresizingMaskIntoConstraints="NO" id="Vy4-dv-jQB">
-                        <rect key="frame" x="18" y="45" width="310" height="17"/>
+                        <rect key="frame" x="26" y="75" width="310" height="17"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Copyright © 2016 Background Music contributors" placeholderString="" id="ctF-95-uVu">
                            <font key="font" metaFont="system"/>
@ -136,7 +136,7 @@
                        </textFieldCell>
                    </textField>
                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="3" translatesAutoresizingMaskIntoConstraints="NO" id="nx6-kQ-N8Z" customClass="BGMLinkField">
-                        <rect key="frame" x="18" y="20" width="310" height="17"/>
+                        <rect key="frame" x="26" y="50" width="310" height="17"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" tag="3" title="https://github.com/kyleneideck/BackgroundMusic" placeholderString="" id="VOb-5X-o3R">
                            <font key="font" metaFont="system"/>
@ -145,7 +145,7 @@
                        </textFieldCell>
                    </textField>
                    <imageView wantsLayer="YES" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Tui-Hf-FLv">
-                        <rect key="frame" x="98" y="125" width="150" height="150"/>
+                        <rect key="frame" x="106" y="155" width="150" height="150"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <shadow key="shadow">
                            <color key="color" white="0.0" alpha="1" colorSpace="calibratedWhite"/>
@ -153,7 +153,7 @@
                        <imageCell key="cell" refusesFirstResponder="YES" alignment="left" animates="YES" imageScaling="proportionallyUpOrDown" image="FermataIcon" id="dBU-ZS-ZzA"/>
                    </imageView>
                    <imageView wantsLayer="YES" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="R1R-Rd-xPC">
-                        <rect key="frame" x="98" y="125" width="150" height="150"/>
+                        <rect key="frame" x="106" y="155" width="150" height="150"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <shadow key="shadow">
                            <color key="color" white="0.0" alpha="1" colorSpace="calibratedWhite"/>
@ -161,19 +161,22 @@
                        <imageCell key="cell" refusesFirstResponder="YES" alignment="left" animates="YES" imageScaling="proportionallyUpOrDown" image="FermataIcon" id="1VP-dU-RCe"/>
                    </imageView>
                    <scrollView fixedFrame="YES" horizontalLineScroll="10" horizontalPageScroll="10" verticalLineScroll="10" verticalPageScroll="10" hasHorizontalScroller="NO" usesPredominantAxisScrolling="NO" translatesAutoresizingMaskIntoConstraints="NO" id="eqz-ap-PAC">
-                        <rect key="frame" x="369" y="20" width="427" height="245"/>
+                        <rect key="frame" x="393" y="45" width="567" height="245"/>
                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                        <clipView key="contentView" ambiguous="YES" id="Cdb-RA-YK0">
-                            <rect key="frame" x="1" y="1" width="425" height="243"/>
+                            <rect key="frame" x="1" y="1" width="565" height="243"/>
                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                            <subviews>
-                                <textView ambiguous="YES" editable="NO" importsGraphics="NO" usesFontPanel="YES" findStyle="panel" continuousSpellChecking="YES" allowsUndo="YES" usesRuler="YES" allowsNonContiguousLayout="YES" quoteSubstitution="YES" dashSubstitution="YES" smartInsertDelete="YES" id="LSG-PF-cl8">
-                                    <rect key="frame" x="0.0" y="0.0" width="425" height="243"/>
+                                <textView ambiguous="YES" editable="NO" importsGraphics="NO" richText="NO" id="LSG-PF-cl8">
+                                    <rect key="frame" x="-4" y="0.0" width="572" height="243"/>
                                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
-                                    <size key="minSize" width="425" height="243"/>
-                                    <size key="maxSize" width="477" height="10000000"/>
+                                    <size key="minSize" width="565" height="243"/>
+                                    <size key="maxSize" width="594" height="10000000"/>
                                    <color key="insertionPointColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                    <allowedInputSourceLocales>
+                                        <string>NSAllRomanInputSourcesLocaleIdentifier</string>
+                                    </allowedInputSourceLocales>
                                </textView>
                            </subviews>
                            <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
@ -183,13 +186,22 @@
                            <autoresizingMask key="autoresizingMask"/>
                        </scroller>
                        <scroller key="verticalScroller" verticalHuggingPriority="750" horizontal="NO" id="qCC-lY-zQ6">
-                            <rect key="frame" x="410" y="1" width="16" height="243"/>
+                            <rect key="frame" x="550" y="1" width="16" height="243"/>
                            <autoresizingMask key="autoresizingMask"/>
                        </scroller>
                    </scrollView>
+                    <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="6qu-yI-r00">
+                        <rect key="frame" x="391" y="20" width="203" height="11"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                        <textFieldCell key="cell" sendsActionOnEndEditing="YES" title="The AirPlay Logo is a trademark of Apple Inc." id="lx7-k3-q16">
+                            <font key="font" metaFont="miniSystem"/>
+                            <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                            <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                        </textFieldCell>
+                    </textField>
                </subviews>
            </view>
-            <point key="canvasLocation" x="-31" y="220"/>
+            <point key="canvasLocation" x="-177" y="232.5"/>
        </window>
        <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" setsMaxLayoutWidthAtFirstLayout="YES" id="IoN-sN-cCx">
            <rect key="frame" x="0.0" y="0.0" width="471" height="180"/>
--- a/BGMApp/BGMApp/Images.xcassets/AirPlayIcon.imageset/AirPlay.pdf
+++ b/BGMApp/BGMApp/Images.xcassets/AirPlayIcon.imageset/AirPlay.pdf
--- a/BGMApp/BGMApp/Images.xcassets/AirPlayIcon.imageset/Contents.json
+++ b/BGMApp/BGMApp/Images.xcassets/AirPlayIcon.imageset/Contents.json
@ -0,0 +1,21 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "filename" : "AirPlay.pdf",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}
--- a/BGMApp/BGMApp/Preferences/BGMAboutPanel.m
+++ b/BGMApp/BGMApp/Preferences/BGMAboutPanel.m
@ -113,6 +113,11 @@ static NSInteger const kProjectWebsiteLabelTag = 3;
        }
        
        licenseView.string = licenseStr;
+        
+        NSFont* __nullable font = [NSFont fontWithName:@"Andale Mono" size:0.0];
+        if (font) {
+            licenseView.textStorage.font = font;
+        }
    }
 }

--- a/BGMApp/BGMApp/Preferences/BGMOutputDevicePrefs.mm
+++ b/BGMApp/BGMApp/Preferences/BGMOutputDevicePrefs.mm
@ -55,46 +55,145 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
    for (NSMenuItem* item in outputDeviceMenuItems) {
        [prefsMenu removeItem:item];
    }
-    [outputDeviceMenuItems removeAllObjects];
    
-    // Insert menu items after the item for the "Output Device" heading
-    const NSInteger menuItemsIdx = [prefsMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
+    [outputDeviceMenuItems removeAllObjects];
    
    // Add a menu item for each output device
    CAHALAudioSystemObject audioSystem;
    UInt32 numDevices = audioSystem.GetNumberAudioDevices();
+    
    if (numDevices > 0) {
        CAAutoArrayDelete<AudioObjectID> devices(numDevices);
        audioSystem.GetAudioDevices(numDevices, devices);
        
        for (UInt32 i = 0; i < numDevices; i++) {
            CAHALAudioDevice device(devices[i]);
-            
-            // TODO: Handle C++ exceptions. (And the ones above that we don't swallow.)
-            BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::populatePreferencesMenu", [&]() {
-                BOOL hasOutputChannels = device.GetTotalNumberChannels(/* inIsInput = */ false) > 0;
-                
-                if (device.GetObjectID() != [audioDevices bgmDevice].GetObjectID() && hasOutputChannels) {
-                    NSString* deviceName = CFBridgingRelease(device.CopyName());
-                    NSMenuItem* item = [[NSMenuItem alloc] initWithTitle:deviceName
-                                                                  action:@selector(outputDeviceWasChanged:)
-                                                           keyEquivalent:@""];
-                    
-                    BOOL selected = [audioDevices isOutputDevice:device.GetObjectID()];
-                    item.state = (selected ? NSOnState : NSOffState);
-                    item.target = self;
-                    item.indentationLevel = 1;
-                    item.representedObject = [NSNumber numberWithUnsignedInt:device.GetObjectID()];
-                    
-                    [prefsMenu insertItem:item atIndex:menuItemsIdx];
-                    
-                    [outputDeviceMenuItems addObject:item];
-                }
-            });
+            [self insertMenuItemsForDevice:device preferencesMenu:prefsMenu];
        }
    }
 }

+- (void) insertMenuItemsForDevice:(CAHALAudioDevice)device preferencesMenu:(NSMenu*)prefsMenu {
+    // Insert menu items after the item for the "Output Device" heading.
+    const NSInteger menuItemsIdx = [prefsMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
+    
+    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::insertMenuItemsForDevice", [&]() {
+        BOOL isBGMDevice = (device.GetObjectID() == [audioDevices bgmDevice].GetObjectID());
+        BOOL isHidden = device.IsHidden();
+        BOOL hasOutputChannels = device.GetTotalNumberChannels(/* inIsInput = */ false) > 0;
+        BOOL canBeDefault = device.CanBeDefaultDevice(/* inIsInput = */ false, /* inIsSystem = */ false);
+        
+        if (!isBGMDevice && !isHidden && hasOutputChannels && canBeDefault) {
+            for (NSMenuItem* item : [self createMenuItemsForDevice:device]) {
+                [prefsMenu insertItem:item atIndex:menuItemsIdx];
+                [outputDeviceMenuItems addObject:item];
+            }
+        }
+    });
+}
+
+- (NSArray<NSMenuItem*>*) createMenuItemsForDevice:(CAHALAudioDevice)device {
+    // We fill this array with a menu item for each output device (or each data source for each device) on
+    // the system.
+    NSMutableArray<NSMenuItem*>* items = [NSMutableArray new];
+
+    AudioObjectPropertyScope scope = kAudioObjectPropertyScopeOutput;
+    UInt32 channel = 0;  // 0 is the master channel.
+    
+    // If the device has data sources, create a menu item for each. Otherwise, create a single menu item
+    // for the device. This way the menu items' titles will be, for example, "Internal Speakers" rather
+    // than "Built-in Output".
+    //
+    // TODO: Handle data destinations as well? I don't have (or know of) any hardware with them.
+    // 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", [&]() {
+        if (device.HasDataSourceControl(scope, channel) &&
+                device.DataSourceControlIsSettable(scope, channel)) {
+            numDataSources = device.GetNumberAvailableDataSources(scope, channel);
+        }
+    });
+    
+    if (numDataSources > 0) {
+        UInt32 dataSourceIDs[numDataSources];
+        // This call updates numDataSources to the real number of IDs it added to our array.
+        device.GetAvailableDataSources(scope, channel, numDataSources, dataSourceIDs);
+        
+        for (UInt32 i = 0; i < numDataSources; i++) {
+            DebugMsg("BGMOutputDevicePrefs::createMenuItemsForDevice: Creating item. %s%u %s%u",
+                     "Device ID:", device.GetObjectID(),
+                     ", Data source ID:", dataSourceIDs[i]);
+            
+            BGMLogAndSwallowExceptionsMsg("BGMOutputDevicePrefs::createMenuItemsForDevice", "(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
+                                                         title:dataSourceName
+                                                       toolTip:deviceName]];
+            });
+        }
+    } else {
+        DebugMsg("BGMOutputDevicePrefs::createMenuItemsForDevice: Creating item. %s%u",
+                 "Device ID:", device.GetObjectID());
+        
+        BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemsForDevice", [&]() {
+            [items addObject:[self createMenuItemForDevice:device
+                                              dataSourceID:nil
+                                                     title:CFBridgingRelease(device.CopyName())
+                                                   toolTip:nil]];
+        });
+    }
+    
+    return items;
+}
+
+- (NSMenuItem*) createMenuItemForDevice:(CAHALAudioDevice)device
+                           dataSourceID:(NSNumber* __nullable)dataSourceID
+                                  title:(NSString* __nullable)title
+                                toolTip:(NSString* __nullable)toolTip {
+    // If we don't have a title, use the tool-tip text instead.
+    if (!title) {
+        title = (toolTip ? toolTip : @"");
+    }
+    
+    NSMenuItem* item = [[NSMenuItem alloc] initWithTitle:BGMNN(title)
+                                                  action:@selector(outputDeviceWasChanged:)
+                                           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", [&]() {
+        if (device.GetTransportType() == kAudioDeviceTransportTypeAirPlay) {
+            item.image = [NSImage imageNamed:@"AirPlayIcon"];
+            
+            // Make the icon a "template image" so it gets drawn colour-inverted when it's highlighted or
+            // OS X is in dark mode.
+            [item.image setTemplate:YES];
+        }
+    });
+    
+    // The menu item should be selected if it's the menu item for the current output device. If the device
+    // has data sources, only the menu item for the current data source should be selected.
+    BOOL isSelected =
+        [audioDevices isOutputDevice:device.GetObjectID()] &&
+            (!dataSourceID || [audioDevices isOutputDataSource:[dataSourceID unsignedIntValue]]);
+    
+    item.state = (isSelected ? NSOnState : NSOffState);
+    item.toolTip = toolTip;
+    item.target = self;
+    item.indentationLevel = 1;
+    item.representedObject = @{ @"deviceID": [NSNumber numberWithUnsignedInt:device.GetObjectID()],
+                                @"dataSourceID": dataSourceID ? BGMNN(dataSourceID) : [NSNull null] };
+    
+    return item;
+}
+
 - (void) outputDeviceWasChanged:(NSMenuItem*)menuItem {
    DebugMsg("BGMOutputDevicePrefs::outputDeviceWasChanged: '%s' menu item selected",
             [menuItem.title UTF8String]);
@ -105,22 +204,59 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
    }
    
    // Change to the new output device.
-    AudioDeviceID newDeviceID = [[menuItem representedObject] unsignedIntValue];
-    NSError* __nullable error = [audioDevices setOutputDeviceWithID:newDeviceID revertOnFailure:YES];
+    AudioDeviceID newDeviceID = [[menuItem representedObject][@"deviceID"] unsignedIntValue];
+    id newDataSourceID = [menuItem representedObject][@"dataSourceID"];
+    
+    BOOL changingDevice = ![audioDevices isOutputDevice:newDeviceID];
+    BOOL changingDataSource =
+        (newDataSourceID != [NSNull null]) &&
+            ![audioDevices isOutputDataSource:[newDataSourceID unsignedIntValue]];
+
+    if (changingDevice || changingDataSource) {
+        NSString* deviceName =
+            menuItem.toolTip ?
+                [NSString stringWithFormat:@"%@ (%@)", menuItem.title, menuItem.toolTip] :
+                menuItem.title;
+        
+        // Dispatched because it usually blocks. (Note that we're using QOS_CLASS_USER_INITIATED
+        // rather than QOS_CLASS_USER_INTERACTIVE.)
+        dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), ^{
+            [self changeToOutputDevice:newDeviceID
+                         newDataSource:newDataSourceID
+                            deviceName:deviceName];
+        });
+    }
+}
+
+- (void) changeToOutputDevice:(AudioDeviceID)deviceID
+                newDataSource:(id)dataSourceID
+                   deviceName:(NSString*)deviceName {
+    NSError* __nullable error;
+    
+    if (dataSourceID == [NSNull null]) {
+        error = [audioDevices setOutputDeviceWithID:deviceID revertOnFailure:YES];
+    } else {
+        error = [audioDevices setOutputDeviceWithID:deviceID
+                                       dataSourceID:[dataSourceID unsignedIntValue]
+                                    revertOnFailure:YES];
+    }
    
    if (error) {
-        // Couldn't change the output device, so show a warning. (No need to change the menu selection back
-        // because it's repopulated every time it's opened.)
-        NSLog(@"Failed to set output device: %@", menuItem);
+        // Couldn't change the output device, so show a warning. (No need to change the menu
+        // selection back because it gets repopulated every time it's opened.)
        
-        NSAlert* alert = [NSAlert new];
-        NSString* deviceName = [menuItem title];
-        
-        alert.messageText =
-            [NSString stringWithFormat:@"Failed to set %@ as the output device", deviceName];
-        alert.informativeText = @"This is probably a bug. Feel free to report it.";
-        
-        [alert runModal];
+        // NSAlerts should only be shown on the main thread.
+        dispatch_async(dispatch_get_main_queue(), ^{
+            NSLog(@"Failed to set output device: %@", deviceName);
+            
+            NSAlert* alert = [NSAlert new];
+            
+            alert.messageText =
+                [NSString stringWithFormat:@"Failed to set %@ as the output device.", deviceName];
+            alert.informativeText = @"This is probably a bug. Feel free to report it.";
+            
+            [alert runModal];
+        });
    }
 }

--- a/BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/Background
+++ b/BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/Background
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0810"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/PublicUtility.xcscheme
+++ b/BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/PublicUtility.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0800"
+   LastUpgradeVersion = "0810"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/SharedSource/BGM_Utils.h
+++ b/SharedSource/BGM_Utils.h
@ -37,6 +37,7 @@
 // System Includes
 #include <mach/error.h>

+#pragma mark Macros

 // The Assert macro from CADebugMacros with support for format strings added.
 #define BGMAssert(inCondition, inMessage, ...)                                  \
@ -46,8 +47,54 @@
        __ASSERT_STOP;                                                          \
    }

+#define BGMAssertNonNull(expression) \
+    BGMAssertNonNull2((expression), #expression)

-#pragma clang assume_nonnull begin
+#define BGMAssertNonNull2(expression, expressionStr) \
+    BGMAssert((expression), \
+              "%s:%d:%s: '%s' is null", \
+              __FILE__, \
+              __LINE__, \
+              __FUNCTION__, \
+              expressionStr);
+
+#pragma mark Objective-C Macros
+
+#if defined(__OBJC__)
+
+#if __has_feature(objc_generics)
+
+// This trick is from https://gist.github.com/robb/d55b72d62d32deaee5fa
+@interface BGMNonNullCastHelper<__covariant T>
+
+- (nonnull T) asNonNull;
+
+@end
+
+// Explicitly casts expressions from nullable to non-null. Only works with expressions that
+// evaluate to Objective-C objects. Use BGM_Utils::NN for other types.
+//
+// TODO: Replace existing non-null casts with this.
+#define BGMNN(expression) ({ \
+        __typeof((expression)) value = (expression); \
+        BGMAssertNonNull2(value, #expression); \
+        BGMNonNullCastHelper<__typeof((expression))>* helper; \
+        (__typeof(helper.asNonNull))value; \
+    })
+
+#else /* __has_feature(objc_generics) */
+
+#define BGMNN(expression) ({ \
+        id value = (expression); \
+        BGMAssertNonNull2(value, #expression); \
+        value; \
+    })
+
+#endif /* __has_feature(objc_generics) */
+
+#endif /* defined(__OBJC__) */
+
+#pragma mark C++ Macros

 #if defined(__cplusplus)

@ -75,9 +122,25 @@
 #define BGMLogUnexpectedExceptionsMsg(callerName, message, function) \
    BGM_Utils::LogUnexpectedExceptions(__FILE__, __LINE__, callerName, message, function)

+#endif /* defined(__cplusplus) */
+
+
+#pragma clang assume_nonnull begin
+
+#if defined(__cplusplus)
+
+#pragma mark C++ Utility Functions

 namespace BGM_Utils
 {
+    // Used to explicitly cast from nullable to non-null. For Objective-C objects, use the BGMNN
+    // macro (above).
+    template <typename T>
+    inline T __nonnull NN(T __nullable v) {
+        BGMAssertNonNull(v);
+        return v;
+    }
+    
    // Log (and swallow) errors returned by Mach functions. Returns false if there was an error.
    bool LogIfMachError(const char* callerName,
                        const char* errorReturnedBy,
@ -136,7 +199,6 @@ namespace BGM_Utils
                                     const char* callerName,
                                     const char* __nullable message,
                                     const std::function<void(void)>& function);
-    
 }

 #endif /* defined(__cplusplus) */