Switch to int; attempt to do a better job of initial audio filling.

Machines/Amiga/Amiga.cpp

@@ -215,7 +215,7 @@ class ConcreteMachine:
 			mc68000_.run_for(cycles);
 		}
 
-		void flush_output(Output) final {
+		void flush_output(int) final {
 			chipset_.flush();
 		}
 

Machines/AmstradCPC/AmstradCPC.cpp

@@ -1049,9 +1049,9 @@ template <bool has_fdc> class ConcreteMachine:
 		}
 
 		/// Fields requests to pump all output.
-		void flush_output(Output output) final {
+		void flush_output(int outputs) final {
 			// Just flush the AY.
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				ay_.update();
 				ay_.flush();
 			}

Machines/Apple/AppleII/AppleII.cpp

@@ -810,13 +810,13 @@ template <Analyser::Static::AppleII::Target::Model model> class ConcreteMachine:
 			return Cycles(1);
 		}
 
-		void flush_output(Output output) final {
+		void flush_output(int outputs) final {
 			update_just_in_time_cards();
 
-			if(int(output) & int(Output::Video)) {
+			if(outputs & Output::Video) {
 				update_video();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/Apple/AppleIIgs/AppleIIgs.cpp

@@ -326,14 +326,14 @@ class ConcreteMachine:
 			m65816_.run_for(cycles);
 		}
 
-		void flush_output(Output output) final {
+		void flush_output(int outputs) final {
 			iwm_.flush();
 			adb_glu_.flush();
 
-			if(int(output) & int(Output::Video)) {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				AudioUpdater updater(this);
 				audio_queue_.perform();
 			}

Machines/Apple/Macintosh/Macintosh.cpp

@@ -365,7 +365,7 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 			return delay;
 		}
 
-		void flush_output(Output) {
+		void flush_output(int) {
 			// Flush the video before the audio queue; in a Mac the
 			// video is responsible for providing part of the
 			// audio signal, so the two aren't as distinct as in

Machines/Atari/2600/Atari2600.cpp

@@ -174,7 +174,7 @@ class ConcreteMachine:
 			bus_->apply_confidence(confidence_counter_);
 		}
 
-		void flush_output(Output) final {
+		void flush_output(int) final {
 			bus_->flush();
 		}
 

Machines/Atari/ST/AtariST.cpp

@@ -413,16 +413,16 @@ class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		void flush_output(Output output) final {
+		void flush_output(int outputs) final {
 			dma_.flush();
 			mfp_.flush();
 			keyboard_acia_.flush();
 			midi_acia_.flush();
 
-			if(int(output) & int(Output::Video)) {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/ColecoVision/ColecoVision.cpp

@@ -342,11 +342,11 @@ class ConcreteMachine:
 			return penalty;
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				vdp_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/Commodore/Vic-20/Vic20.cpp

@@ -620,11 +620,11 @@ class ConcreteMachine:
 			return Cycles(1);
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				update_video();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				mos6560_.flush();
 			}
 		}

Machines/Electron/Electron.cpp

@@ -501,11 +501,11 @@ template <bool has_scsi_bus> class ConcreteMachine:
 			return Cycles(int(cycles));
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/Enterprise/Enterprise.cpp

@@ -539,11 +539,11 @@ template <bool has_disk_controller, bool is_6mhz> class ConcreteMachine:
 			return penalty;
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				nick_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/MSX/MSX.cpp

@@ -615,11 +615,11 @@ class ConcreteMachine:
 			return addition;
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				vdp_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/MasterSystem/MasterSystem.cpp

@@ -210,11 +210,11 @@ class ConcreteMachine:
 			z80_.run_for(cycles);
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				vdp_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/Oric/Oric.cpp

@@ -578,11 +578,11 @@ template <Analyser::Static::Oric::Target::DiskInterface disk_interface, CPU::MOS
 			return Cycles(1);
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				via_.flush();
 			}
 			diskii_.flush();

Machines/Sinclair/ZX8081/ZX8081.cpp

@@ -292,13 +292,13 @@ template<bool is_zx81> class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		void flush_output(Output output) final {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) final {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
 
 			if constexpr (is_zx81) {
-				if(int(output) & int(Output::Audio)) {
+				if(outputs & Output::Audio) {
 					update_audio();
 					audio_queue_.perform();
 				}

Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp

@@ -263,12 +263,12 @@ template<Model model> class ConcreteMachine:
 			}
 		}
 
-		void flush_output(Output output) override {
-			if(int(output) & int(Output::Video)) {
+		void flush_output(int outputs) override {
+			if(outputs & Output::Video) {
 				video_.flush();
 			}
 
-			if(int(output) & int(Output::Audio)) {
+			if(outputs & Output::Audio) {
 				update_audio();
 				audio_queue_.perform();
 			}

Machines/TimedMachine.hpp

@@ -61,13 +61,13 @@ class TimedMachine {
 		virtual float get_confidence() { return 0.5f; }
 		virtual std::string debug_type() { return ""; }
 
-		enum class Output {
-			Video = 1 << 0,
-			Audio = 1 << 1
+		struct Output {
+			static constexpr int Video = 1 << 0;
+			static constexpr int Audio = 1 << 1;
 		};
 		/// Ensures all locally-buffered output is posted onward for the types of output indicated
-		/// by the bitfield argument.
-		virtual void flush_output(Output) {}
+		/// by the bitfield argument, which is comprised of flags from the namespace @c Output.
+		virtual void flush_output(int) {}
 
 	protected:
 		/// Runs the machine for @c cycles.

OSBindings/Mac/Clock Signal/Audio/CSAudioQueue.h

@@ -58,4 +58,9 @@
 */
 @property (nonatomic, readonly) NSUInteger preferredBufferSize;
 
+/*!
+	@returns @C YES if this queue is running low or is completely exhausted of new audio buffers.
+*/
+@property (atomic, readonly) BOOL isRunningDry;
+
 @end

OSBindings/Mac/Clock Signal/Audio/CSAudioQueue.m

@@ -8,6 +8,7 @@
 
 #import "CSAudioQueue.h"
 @import AudioToolbox;
+#include <stdatomic.h>
 
 #define AudioQueueBufferMaxLength		8192
 #define NumberOfStoredAudioQueueBuffer	16
@@ -29,7 +30,7 @@ static NSLock *CSAudioQueueDeallocLock;
 	AudioQueueRef _audioQueue;
 	NSLock *_storedBuffersLock;
 	CSWeakAudioQueuePointer *_weakPointer;
-	int _enqueuedBuffers;
+	atomic_int _enqueuedBuffers;
 }
 
 #pragma mark - AudioQueue callbacks
@@ -39,14 +40,14 @@ static NSLock *CSAudioQueueDeallocLock;
 */
 - (BOOL)audioQueue:(AudioQueueRef)theAudioQueue didCallbackWithBuffer:(AudioQueueBufferRef)buffer {
 	[_storedBuffersLock lock];
-	--_enqueuedBuffers;
+	const int buffers = atomic_fetch_add(&_enqueuedBuffers, -1);
 
 	// If that leaves nothing in the queue, re-enqueue whatever just came back in order to keep the
 	// queue going. AudioQueues seem to stop playing and never restart no matter how much encouragement
 	// if exhausted.
-	if(!_enqueuedBuffers) {
+	if(!buffers) {
 		AudioQueueEnqueueBuffer(theAudioQueue, buffer, 0, NULL);
-		++_enqueuedBuffers;
+		atomic_fetch_add(&_enqueuedBuffers, 1);
 	} else {
 		AudioQueueFreeBuffer(_audioQueue, buffer);
 	}
@@ -71,6 +72,10 @@ static void audioOutputCallback(
 	}
 }
 
+- (BOOL)isRunningDry {
+	return atomic_load_explicit(&_enqueuedBuffers, memory_order_relaxed) < 2;
+}
+
 #pragma mark - Standard object lifecycle
 
 - (instancetype)initWithSamplingRate:(Float64)samplingRate isStereo:(BOOL)isStereo {
@@ -158,11 +163,11 @@ static void audioOutputCallback(
 
 	[_storedBuffersLock lock];
 	// Don't enqueue more than 4 buffers ahead of now, to ensure not too much latency accrues.
-	if(_enqueuedBuffers > 4) {
+	if(atomic_load_explicit(&_enqueuedBuffers, memory_order_relaxed) > 4) {
 		[_storedBuffersLock unlock];
 		return;
 	}
-	++_enqueuedBuffers;
+	atomic_fetch_add(&_enqueuedBuffers, 1);
 
 	AudioQueueBufferRef newBuffer;
 	AudioQueueAllocateBuffer(_audioQueue, (UInt32)bufferBytes * 2, &newBuffer);

OSBindings/Mac/Clock Signal/Machine/CSMachine.mm

@@ -678,13 +678,21 @@ struct ActivityObserver: public Activity::Observer {
 
 - (void)audioQueueIsRunningDry:(nonnull CSAudioQueue *)audioQueue {
 	updater.update([self] {
-		updater.performer.machine->flush_output(MachineTypes::TimedMachine::Output::Audio);
+		updater.performer.machine->flush_output(MachineTypes::TimedMachine::Output::Audio);// | MachineTypes::TimedMachine::Output::Video);
+//		dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0), ^{
+//			[self.view updateBacking];
+//		});
 	});
 }
 
 - (void)scanTargetViewDisplayLinkDidFire:(CSScanTargetView *)view now:(const CVTimeStamp *)now outputTime:(const CVTimeStamp *)outputTime {
 	updater.update([self] {
-		updater.performer.machine->flush_output(MachineTypes::TimedMachine::Output::Video);
+		auto outputs = MachineTypes::TimedMachine::Output::Video;
+		if(_audioQueue.isRunningDry) {
+			outputs |= MachineTypes::TimedMachine::Output::Audio;
+		}
+		updater.performer.machine->flush_output(outputs);
+
 		dispatch_async(dispatch_get_main_queue(), ^{
 			[self.view updateBacking];
 			[self.view draw];