Merge pull request #842 from TomHarte/QtMouseEscape

Adds F8+F12 as an alternative mouse-release combo for Qt.

Components/6522/6522.hpp

@@ -128,13 +128,14 @@ template <class T> class MOS6522: public MOS6522Storage {
 
 		void access(int address);
 
-		uint8_t get_port_input(Port port, uint8_t output_mask, uint8_t output);
+		uint8_t get_port_input(Port port, uint8_t output_mask, uint8_t output, uint8_t timer_mask);
 		inline void reevaluate_interrupts();
 
 		/// Sets the current intended output value for the port and line;
 		/// if this affects the visible output, it will be passed to the handler.
 		void set_control_line_output(Port port, Line line, LineState value);
 		void evaluate_cb2_output();
+		void evaluate_port_b_output();
 };
 
 }

Components/6522/Implementation/6522Implementation.hpp

@@ -8,6 +8,10 @@
 
 #include "../../../Outputs/Log.hpp"
 
+// As-yet unimplemented (incomplete list):
+//
+//	PB6 count-down mode for timer 2.
+
 namespace MOS {
 namespace MOS6522 {
 
@@ -34,18 +38,18 @@ template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
 	address &= 0xf;
 	access(address);
 	switch(address) {
-		case 0x0:	// Write Port B.
+		case 0x0:	// Write Port B. ('ORB')
 			// Store locally and communicate outwards.
 			registers_.output[1] = value;
 
 			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
-			bus_handler_.set_port_output(Port::B, value, registers_.data_direction[1]);
+			evaluate_port_b_output();
 
 			registers_.interrupt_flags &= ~(InterruptFlag::CB1ActiveEdge | ((registers_.peripheral_control&0x20) ? 0 : InterruptFlag::CB2ActiveEdge));
 			reevaluate_interrupts();
 		break;
 		case 0xf:
-		case 0x1:	// Write Port A.
+		case 0x1:	// Write Port A. ('ORA')
 			registers_.output[0] = value;
 
 			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
@@ -59,28 +63,44 @@ template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
 			reevaluate_interrupts();
 		break;
 
-		case 0x2:	// Port B direction.
+		case 0x2:	// Port B direction ('DDRB').
 			registers_.data_direction[1] = value;
 		break;
-		case 0x3:	// Port A direction.
+		case 0x3:	// Port A direction ('DDRA').
 			registers_.data_direction[0] = value;
 		break;
 
 		// Timer 1
-		case 0x6:	case 0x4:	registers_.timer_latch[0] = (registers_.timer_latch[0]&0xff00) | value;	break;
-		case 0x5:	case 0x7:
+		case 0x6:	case 0x4:	// ('T1L-L' and 'T1C-L')
+			registers_.timer_latch[0] = (registers_.timer_latch[0]&0xff00) | value;
+		break;
+		case 0x7:	// Timer 1 latch, high ('T1L-H').
 			registers_.timer_latch[0] = (registers_.timer_latch[0]&0x00ff) | uint16_t(value << 8);
-			registers_.interrupt_flags &= ~InterruptFlag::Timer1;
-			if(address == 0x05) {
-				registers_.next_timer[0] = registers_.timer_latch[0];
-				timer_is_running_[0] = true;
+		break;
+		case 0x5:	// Timer 1 counter, high ('T1C-H').
+			// Fill latch.
+			registers_.timer_latch[0] = (registers_.timer_latch[0]&0x00ff) | uint16_t(value << 8);
+
+			// Restart timer.
+			registers_.next_timer[0] = registers_.timer_latch[0];
+			timer_is_running_[0] = true;
+
+			// If PB7 output mode is active, set it low.
+			if(timer1_is_controlling_pb7()) {
+				registers_.timer_port_b_output &= 0x7f;
+				evaluate_port_b_output();
 			}
+
+			// Clear existing interrupt flag.
+			registers_.interrupt_flags &= ~InterruptFlag::Timer1;
 			reevaluate_interrupts();
 		break;
 
 		// Timer 2
-		case 0x8:	registers_.timer_latch[1] = value;	break;
-		case 0x9:
+		case 0x8:	// ('T2C-L')
+			registers_.timer_latch[1] = value;
+		break;
+		case 0x9:	// ('T2C-H')
 			registers_.interrupt_flags &= ~InterruptFlag::Timer2;
 			registers_.next_timer[1] = registers_.timer_latch[1] | uint16_t(value << 8);
 			timer_is_running_[1] = true;
@@ -88,7 +108,7 @@ template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
 		break;
 
 		// Shift
-		case 0xa:
+		case 0xa:	// ('SR')
 			registers_.shift = value;
 			shift_bits_remaining_ = 8;
 			registers_.interrupt_flags &= ~InterruptFlag::ShiftRegister;
@@ -96,11 +116,18 @@ template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
 		break;
 
 		// Control
-		case 0xb:
+		case 0xb:	// Auxiliary control ('ACR').
 			registers_.auxiliary_control = value;
 			evaluate_cb2_output();
+
+			// This is a bit of a guess: reset the timer-based PB7 output to its default high level
+			// any timer that timer-linked PB7 output is disabled.
+			if(!timer1_is_controlling_pb7()) {
+				registers_.timer_port_b_output |= 0x80;
+			}
+			evaluate_port_b_output();
 		break;
-		case 0xc: {
+		case 0xc: {	// Peripheral control ('PCR').
 //			const auto old_peripheral_control = registers_.peripheral_control;
 			registers_.peripheral_control = value;
 
@@ -141,11 +168,11 @@ template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
 		} break;
 
 		// Interrupt control
-		case 0xd:
+		case 0xd:	// Interrupt flag regiser ('IFR').
 			registers_.interrupt_flags &= ~value;
 			reevaluate_interrupts();
 		break;
-		case 0xe:
+		case 0xe:	// Interrupt enable register ('IER').
 			if(value&0x80)
 				registers_.interrupt_enable |= value;
 			else
@@ -159,54 +186,55 @@ template <typename T> uint8_t MOS6522<T>::read(int address) {
 	address &= 0xf;
 	access(address);
 	switch(address) {
-		case 0x0:
+		case 0x0:	// Read Port B ('IRB').
 			registers_.interrupt_flags &= ~(InterruptFlag::CB1ActiveEdge | InterruptFlag::CB2ActiveEdge);
 			reevaluate_interrupts();
-		return get_port_input(Port::B, registers_.data_direction[1], registers_.output[1]);
+		return get_port_input(Port::B, registers_.data_direction[1], registers_.output[1], registers_.auxiliary_control & 0x80);
 		case 0xf:
-		case 0x1:
+		case 0x1:	// Read Port A ('IRA').
 			registers_.interrupt_flags &= ~(InterruptFlag::CA1ActiveEdge | InterruptFlag::CA2ActiveEdge);
 			reevaluate_interrupts();
-		return get_port_input(Port::A, registers_.data_direction[0], registers_.output[0]);
+		return get_port_input(Port::A, registers_.data_direction[0], registers_.output[0], 0);
 
-		case 0x2:	return registers_.data_direction[1];
-		case 0x3:	return registers_.data_direction[0];
+		case 0x2:	return registers_.data_direction[1];	// Port B direction ('DDRB').
+		case 0x3:	return registers_.data_direction[0];	// Port A direction ('DDRA').
 
 		// Timer 1
-		case 0x4:
+		case 0x4:	// Timer 1 low-order latches ('T1L-L').
 			registers_.interrupt_flags &= ~InterruptFlag::Timer1;
 			reevaluate_interrupts();
 		return registers_.timer[0] & 0x00ff;
-		case 0x5:	return registers_.timer[0] >> 8;
-		case 0x6:	return registers_.timer_latch[0] & 0x00ff;
-		case 0x7:	return registers_.timer_latch[0] >> 8;
+		case 0x5:	return registers_.timer[0] >> 8;			// Timer 1 high-order counter ('T1C-H')
+		case 0x6:	return registers_.timer_latch[0] & 0x00ff;	// Timer 1 low-order latches ('T1L-L').
+		case 0x7:	return registers_.timer_latch[0] >> 8;		// Timer 1 high-order latches ('T1L-H').
 
 		// Timer 2
-		case 0x8:
+		case 0x8:	// Timer 2 low-order counter ('T2C-L').
 			registers_.interrupt_flags &= ~InterruptFlag::Timer2;
 			reevaluate_interrupts();
 		return registers_.timer[1] & 0x00ff;
-		case 0x9:	return registers_.timer[1] >> 8;
+		case 0x9:	return registers_.timer[1] >> 8;	// Timer 2 high-order counter ('T2C-H').
 
-		case 0xa:
+		case 0xa:	// Shift register ('SR').
 			shift_bits_remaining_ = 8;
 			registers_.interrupt_flags &= ~InterruptFlag::ShiftRegister;
 			reevaluate_interrupts();
 		return registers_.shift;
 
-		case 0xb:	return registers_.auxiliary_control;
-		case 0xc:	return registers_.peripheral_control;
+		case 0xb:	return registers_.auxiliary_control;	// Auxiliary control ('ACR').
+		case 0xc:	return registers_.peripheral_control;	// Peripheral control ('PCR').
 
-		case 0xd:	return registers_.interrupt_flags | (get_interrupt_line() ? 0x80 : 0x00);
-		case 0xe:	return registers_.interrupt_enable | 0x80;
+		case 0xd:	return registers_.interrupt_flags | (get_interrupt_line() ? 0x80 : 0x00);	// Interrupt flag register ('IFR').
+		case 0xe:	return registers_.interrupt_enable | 0x80;									// Interrupt enable register ('IER').
 	}
 
 	return 0xff;
 }
 
-template <typename T> uint8_t MOS6522<T>::get_port_input(Port port, uint8_t output_mask, uint8_t output) {
+template <typename T> uint8_t MOS6522<T>::get_port_input(Port port, uint8_t output_mask, uint8_t output, uint8_t timer_mask) {
 	bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
 	const uint8_t input = bus_handler_.get_port_input(port);
+	output = (output & ~timer_mask) | (registers_.timer_port_b_output & timer_mask);
 	return (input & ~output_mask) | (output & output_mask);
 }
 
@@ -276,10 +304,13 @@ template <typename T> void MOS6522<T>::do_phase2() {
 		registers_.timer_needs_reload = false;
 		registers_.timer[0] = registers_.timer_latch[0];
 	} else {
-		registers_.timer[0] --;
+		-- registers_.timer[0];
 	}
 
-	registers_.timer[1] --;
+	// Count down timer 2 if it is in timed interrupt mode (i.e. auxiliary control bit 5 is clear).
+	registers_.timer[1] -= timer2_clock_decrement();
+
+	// TODO: can eliminate conditional branches here.
 	if(registers_.next_timer[0] >= 0) {
 		registers_.timer[0] = uint16_t(registers_.next_timer[0]);
 		registers_.next_timer[0] = -1;
@@ -330,20 +361,29 @@ template <typename T> void MOS6522<T>::do_phase1() {
 		reevaluate_interrupts();
 
 		// Determine whether to reload.
-		if(registers_.auxiliary_control&0x40)
+		if(timer1_is_continuous())
 			registers_.timer_needs_reload = true;
 		else
 			timer_is_running_[0] = false;
 
 		// Determine whether to toggle PB7.
-		if(registers_.auxiliary_control&0x80) {
-			registers_.output[1] ^= 0x80;
+		if(timer1_is_controlling_pb7()) {
+			registers_.timer_port_b_output ^= 0x80;
 			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
-			bus_handler_.set_port_output(Port::B, registers_.output[1], registers_.data_direction[1]);
+			evaluate_port_b_output();
 		}
 	}
 }
 
+template <typename T> void MOS6522<T>::evaluate_port_b_output() {
+	// Apply current timer-linked PB7 output if any atop the stated output.
+	const uint8_t timer_control_bit = registers_.auxiliary_control & 0x80;
+	bus_handler_.set_port_output(
+		Port::B,
+		(registers_.output[1] & (0xff ^ timer_control_bit)) | timer_control_bit,
+		registers_.data_direction[1] | timer_control_bit);
+}
+
 /*! Runs for a specified number of half cycles. */
 template <typename T> void MOS6522<T>::run_for(const HalfCycles half_cycles) {
 	auto number_of_half_cycles = half_cycles.as_integral();
@@ -438,10 +478,11 @@ template <typename T> void MOS6522<T>::shift_in() {
 }
 
 template <typename T> void MOS6522<T>::shift_out() {
-	// When shifting out, the shift register rotates rather than strictly shifts.
-	// TODO: is that true for all modes?
-	if(shift_mode() == ShiftMode::OutUnderT2FreeRunning || shift_bits_remaining_) {
-		registers_.shift = uint8_t((registers_.shift << 1) | (registers_.shift >> 7));
+	const bool is_free_running = shift_mode() == ShiftMode::OutUnderT2FreeRunning;
+	if(is_free_running || shift_bits_remaining_) {
+		// Recirculate bits only if in free-running mode (?)
+		const uint8_t incoming_bit = (registers_.shift >> 7) * is_free_running;
+		registers_.shift = uint8_t(registers_.shift << 1) | incoming_bit;
 		evaluate_cb2_output();
 
 		--shift_bits_remaining_;

Components/6522/Implementation/6522Storage.hpp

@@ -34,7 +34,9 @@ class MOS6522Storage {
 			uint8_t peripheral_control = 0;
 			uint8_t interrupt_flags = 0;
 			uint8_t interrupt_enable = 0;
+
 			bool timer_needs_reload = false;
+			uint8_t timer_port_b_output = 0xff;
 		} registers_;
 
 		// Control state.
@@ -79,12 +81,30 @@ class MOS6522Storage {
 			OutUnderPhase2 = 6,
 			OutUnderCB1 = 7
 		};
-		ShiftMode shift_mode() const {
-			return ShiftMode((registers_.auxiliary_control >> 2) & 7);
+		bool timer1_is_controlling_pb7() const {
+			return registers_.auxiliary_control & 0x80;
+		}
+		bool timer1_is_continuous() const {
+			return registers_.auxiliary_control & 0x40;
 		}
 		bool is_shifting_out() const {
 			return registers_.auxiliary_control & 0x10;
 		}
+		int timer2_clock_decrement() const {
+			return 1 ^ ((registers_.auxiliary_control >> 5)&1);
+		}
+		int timer2_pb6_decrement() const {
+			return (registers_.auxiliary_control >> 5)&1;
+		}
+		ShiftMode shift_mode() const {
+			return ShiftMode((registers_.auxiliary_control >> 2) & 7);
+		}
+		bool portb_is_latched() const {
+			return registers_.auxiliary_control & 0x02;
+		}
+		bool port1_is_latched() const {
+			return registers_.auxiliary_control & 0x01;
+		}
 };
 
 }

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -860,6 +860,7 @@
 		4BEF6AAC1D35D1C400E73575 /* DPLLTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BEF6AAB1D35D1C400E73575 /* DPLLTests.swift */; };
 		4BF437EE209D0F7E008CBD6B /* SegmentParser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF437EC209D0F7E008CBD6B /* SegmentParser.cpp */; };
 		4BF437EF209D0F7E008CBD6B /* SegmentParser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BF437EC209D0F7E008CBD6B /* SegmentParser.cpp */; };
+		4BF8D4C82516E27A00BBE21B /* Accelerate.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 4BB8617024E22F4900A00E03 /* Accelerate.framework */; };
 		4BFCA1241ECBDCB400AC40C1 /* AllRAMProcessor.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BFCA1211ECBDCAF00AC40C1 /* AllRAMProcessor.cpp */; };
 		4BFCA1271ECBE33200AC40C1 /* TestMachineZ80.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BFCA1261ECBE33200AC40C1 /* TestMachineZ80.mm */; };
 		4BFCA1291ECBE7A700AC40C1 /* zexall.com in Resources */ = {isa = PBXBuildFile; fileRef = 4BFCA1281ECBE7A700AC40C1 /* zexall.com */; };
@@ -1830,6 +1831,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				4B9F11CA2272433900701480 /* libz.tbd in Frameworks */,
+				4BF8D4C82516E27A00BBE21B /* Accelerate.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme

@@ -67,7 +67,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Release"
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"

OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm

@@ -278,8 +278,9 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	size_t _chromaKernelSize;
 	std::atomic<bool> _isUsingSupersampling;
 
-	// The output view.
+	// The output view and its aspect ratio.
 	__weak MTKView *_view;
+	CGFloat _viewAspectRatio;	// To avoid accessing .bounds away from the main thread.
 }
 
 - (nonnull instancetype)initWithView:(nonnull MTKView *)view {
@@ -357,6 +358,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
  @param size New drawable size in pixels
  */
 - (void)mtkView:(nonnull MTKView *)view drawableSizeWillChange:(CGSize)size {
+	_viewAspectRatio = size.width / size.height;
 	[self setAspectRatio];
 
 	@synchronized(self) {
@@ -522,7 +524,6 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 
 - (void)setAspectRatio {
 	const auto modals = _scanTarget.modals();
-	const auto viewAspectRatio = (_view.bounds.size.width / _view.bounds.size.height);
 	simd::float3x3 sourceToDisplay{1.0f};
 
 	// The starting coordinate space is [0, 1].
@@ -550,7 +551,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	// Determine the correct zoom level. This is a combination of (i) the necessary horizontal stretch to produce a proper
 	// aspect ratio; and (ii) the necessary zoom from there to either fit the visible area width or height as per a decision
 	// on letterboxing or pillarboxing.
-	const float aspectRatioStretch = float(modals.aspect_ratio / viewAspectRatio);
+	const float aspectRatioStretch = float(modals.aspect_ratio / _viewAspectRatio);
 	const float fitWidthZoom = 1.0f / (float(modals.visible_area.size.width) * aspectRatioStretch);
 	const float fitHeightZoom = 1.0f / float(modals.visible_area.size.height);
 	const float zoom = std::min(fitWidthZoom, fitHeightZoom);

OSBindings/Mac/Clock SignalTests/6502TimingTests.swift

@@ -200,7 +200,7 @@ class MOS6502TimingTests: XCTestCase, CSTestMachineTrapHandler {
 	func runTest(_ code: [UInt8], expectedRunLength: UInt32) {
 		machine.trapHandler = self
 
-		let immediateCode = Data(bytes: UnsafePointer<UInt8>(code), count: code.count)
+		let immediateCode = Data(code)
 		machine.setData(immediateCode, atAddress: 0x200)
 		machine.addTrapAddress(UInt16(0x200 + code.count))
 		machine.setValue(0x00, forAddress: 0x0000)

OSBindings/Mac/Clock SignalTests/6522Tests.swift

@@ -101,6 +101,116 @@ class MOS6522Tests: XCTestCase {
 	}
 
 
+	// MARK: PB7 timer 1 tests
+	// These follow the same logic and check for the same results as the VICE VIC-20 via_pb7 tests.
+
+	// Perfoms:
+	//
+	//	(1) establish initial ACR and port B output value, and grab port B input value.
+	//	(2) start timer 1, grab port B input value.
+	//	(3) set final ACR, grab port B input value.
+	//	(4) allow timer 1 to expire, grab port B input value.
+	private func runTest(startACR: UInt8, endACR: UInt8, portBOutput: UInt8) -> [UInt8] {
+		var result: [UInt8] = []
+
+		// Clear all register values.
+		for n: UInt in 0...15 {
+			m6522.setValue(0, forRegister: n)
+		}
+		m6522.run(forHalfCycles: 2)
+
+		// Set data direction and current port B value.
+		m6522.setValue(0xff, forRegister: 2)
+		m6522.run(forHalfCycles: 2)
+		m6522.setValue(portBOutput, forRegister: 0)
+		m6522.run(forHalfCycles: 2)
+
+		// Set initial ACR and grab the current port B value.
+		m6522.setValue(startACR, forRegister: 0xb)
+		m6522.run(forHalfCycles: 2)
+		result.append(m6522.value(forRegister: 0))
+		m6522.run(forHalfCycles: 2)
+
+		// Start timer 1 and grab the value.
+		m6522.setValue(1, forRegister: 0x5)
+		m6522.run(forHalfCycles: 2)
+		result.append(m6522.value(forRegister: 0))
+		m6522.run(forHalfCycles: 2)
+
+		// Set the final ACR value and grab value.
+		m6522.setValue(endACR, forRegister: 0xb)
+		m6522.run(forHalfCycles: 2)
+		result.append(m6522.value(forRegister: 0))
+		m6522.run(forHalfCycles: 2)
+
+		// Make sure timer 1 has expired.
+		m6522.run(forHalfCycles: 512)
+
+		// Grab the final value.
+		result.append(m6522.value(forRegister: 0))
+
+		return result
+	}
+
+	func testTimer1PB7() {
+		// Original top row. [original Vic-20 screen output in comments on the right]
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x00, portBOutput: 0x00), [0x00, 0x00, 0x00, 0x00])	// @@@@	(i.e. 0, 0, 0, 0)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x40, portBOutput: 0x00), [0x00, 0x00, 0x00, 0x00])	// @@@@	(i.e. 0, 0, 0, 0)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x80, portBOutput: 0x00), [0x00, 0x00, 0x80, 0x00])	// @@b@	(i.e. 0, 0, 1, 0)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0xc0, portBOutput: 0x00), [0x00, 0x00, 0x80, 0x00])	// @@b@	(i.e. 0, 0, 1, 0)
+
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x00, portBOutput: 0xff), [0xff, 0xff, 0xff, 0xff])	// cccc	(i.e. 1, 1, 1, 1)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x40, portBOutput: 0xff), [0xff, 0xff, 0xff, 0xff])	// cccc	(i.e. 1, 1, 1, 1)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0x80, portBOutput: 0xff), [0xff, 0xff, 0xff, 0x7f])	// ccca	(i.e. 1, 1, 1, 0)
+		XCTAssertEqual(runTest(startACR: 0x00, endACR: 0xc0, portBOutput: 0xff), [0xff, 0xff, 0xff, 0x7f])	// ccca	(i.e. 1, 1, 1, 0)
+
+		// Second row.	[same output as first row]
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x00, portBOutput: 0x00), [0x00, 0x00, 0x00, 0x00])	// @@@@
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x40, portBOutput: 0x00), [0x00, 0x00, 0x00, 0x00])	// @@@@
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x80, portBOutput: 0x00), [0x00, 0x00, 0x80, 0x00])	// @@b@
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0xc0, portBOutput: 0x00), [0x00, 0x00, 0x80, 0x00])	// @@b@
+
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x00, portBOutput: 0xff), [0xff, 0xff, 0xff, 0xff])	// cccc
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x40, portBOutput: 0xff), [0xff, 0xff, 0xff, 0xff])	// cccc
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0x80, portBOutput: 0xff), [0xff, 0xff, 0xff, 0x7f])	// ccca
+		XCTAssertEqual(runTest(startACR: 0x40, endACR: 0xc0, portBOutput: 0xff), [0xff, 0xff, 0xff, 0x7f])	// ccca
+
+		// Third row.
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x00, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x00])	// b@@@	(i.e. 1, 0, 0, 0)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x40, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x00])	// b@@@	(i.e. 1, 0, 0, 0)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x80, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x80])	// b@@b	(i.e. 1, 0, 0, 1)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0xc0, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x80])	// b@@b	(i.e. 1, 0, 0, 1)
+
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x00, portBOutput: 0xff), [0xff, 0x7f, 0xff, 0xff])	// cacc	(i.e. 1, 0, 1, 1)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x40, portBOutput: 0xff), [0xff, 0x7f, 0xff, 0xff])	// cacc	(i.e. 1, 0, 1, 1)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0x80, portBOutput: 0xff), [0xff, 0x7f, 0x7f, 0xff])	// caac	(i.e. 1, 0, 0, 1)
+		XCTAssertEqual(runTest(startACR: 0x80, endACR: 0xc0, portBOutput: 0xff), [0xff, 0x7f, 0x7f, 0xff])	// caac	(i.e. 1, 0, 0, 1)
+
+		// Final row.	[same output as third row]
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x00, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x00])	// b@@@
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x40, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x00])	// b@@@
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x80, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x80])	// b@@b
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0xc0, portBOutput: 0x00), [0x80, 0x00, 0x00, 0x80])	// b@@b
+
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x00, portBOutput: 0xff), [0xff, 0x7f, 0xff, 0xff])	// cacc
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x40, portBOutput: 0xff), [0xff, 0x7f, 0xff, 0xff])	// cacc
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0x80, portBOutput: 0xff), [0xff, 0x7f, 0x7f, 0xff])	// caac
+		XCTAssertEqual(runTest(startACR: 0xc0, endACR: 0xc0, portBOutput: 0xff), [0xff, 0x7f, 0x7f, 0xff])	// caac
+
+		// Conclusions:
+		//
+		//	after inital ACR and port B value:	[original data if not in PB7 output mode, otherwise 1]
+		//	after starting timer 1: 			[original data if not in PB7 output mode, otherwise 0]
+		//	after final ACR value:				[original data if not in PB7 output mode, 1 if has transitioned to PB7 mode, 0 if was already in PB7 mode]
+		//	after timer 1 expiry:				[original data if not in PB7 mode, 1 if timer has expired while in PB7 mode]
+		//
+		//	i.e.
+		//		(1)	there is separate storage for the programmer-set PB7 and the timer output;
+		//		(2)	the timer output is reset upon a timer write only if PB7 output is enabled;
+		//		(3)	expiry toggles the output.
+	}
+
+
 	// MARK: Data direction tests
 	func testDataDirection() {
 		// set low four bits of register B as output, the top four as input

OSBindings/Mac/Clock SignalTests/PCMSegmentEventSourceTests.mm

@@ -70,12 +70,9 @@
 
 - (void)testSeekToSecondBit {
 	Storage::Disk::PCMSegmentEventSource segmentSource = self.segmentSource;
-	Storage::Time target_time(1, 10);
 
-	Storage::Time found_time = segmentSource.seek_to(target_time);
-	found_time.simplify();
-
-	XCTAssertTrue(found_time.length == 1 && found_time.clock_rate == 20, @"A request to seek to 1/10th should have seeked to 1/20th");
+	const float found_time = segmentSource.seek_to(1.0f / 10.0f);
+	XCTAssertTrue(fabsf(found_time - 1.0f / 20.0f) < 0.01f, @"A request to seek to 1/10th should have seeked to 1/20th");
 
 	Storage::Disk::Track::Event next_event = segmentSource.get_next_event();
 	next_event.length.simplify();
@@ -85,12 +82,9 @@
 
 - (void)testSeekBeyondFinalBit {
 	Storage::Disk::PCMSegmentEventSource segmentSource = self.segmentSource;
-	Storage::Time target_time(24, 10);
+	const float found_time = segmentSource.seek_to(2.4f);
 
-	Storage::Time found_time = segmentSource.seek_to(target_time);
-	found_time.simplify();
-
-	XCTAssertTrue(found_time.length == 47 && found_time.clock_rate == 20, @"A request to seek to 24/10ths should have seeked to 47/20ths");
+	XCTAssertTrue(fabsf(found_time - 47.0f / 20.0f) < 0.01f, @"A request to seek to 24/10ths should have seeked to 47/20ths");
 
 	Storage::Disk::Track::Event next_event = segmentSource.get_next_event();
 	next_event.length.simplify();

OSBindings/Mac/Clock SignalTests/PCMTrackTests.mm

@@ -73,16 +73,14 @@
 	}
 
 	Storage::Disk::PCMTrack track(segments);
-	Storage::Time late_time(967445, 2045454);
+	const float late_time = 967445.0f / 2045454.0f;
 	const auto offset = track.seek_to(late_time);
 	XCTAssert(offset <= late_time, "Found location should be at or before sought time");
 
 	const auto difference = late_time - offset;
-	const double difference_duration = difference.get<double>();
-	XCTAssert(difference_duration >= 0.0 && difference_duration < 0.005, "Next event should occur soon");
+	XCTAssert(difference >= 0.0 && difference < 0.005, "Next event should occur soon");
 
-	const double offset_duration = offset.get<double>();
-	XCTAssert(offset_duration >= 0.0 && offset_duration < 0.5, "Next event should occur soon");
+	XCTAssert(offset >= 0.0 && offset < 0.5, "Next event should occur soon");
 
 	auto next_event = track.get_next_event();
 	double next_event_duration = next_event.length.get<double>();

OSBindings/Qt/mainwindow.cpp

@@ -812,7 +812,7 @@ void MainWindow::setWindowTitle() {
 		break;
 	}
 
-	if(mouseIsCaptured) title += " (press control+escape to release mouse)";
+	if(mouseIsCaptured) title += " (press control+escape or F8+F12 to release mouse)";
 
 	QMainWindow::setWindowTitle(title);
 }

OSBindings/Qt/scantargetwidget.cpp

@@ -142,12 +142,25 @@ void ScanTargetWidget::setMouseDelegate(MouseDelegate *delegate) {
 	setMouseTracking(delegate);
 }
 
+void ScanTargetWidget::keyReleaseEvent(QKeyEvent *event) {
+	// Releasing F8 or F12 needs to be tracked but doesn't actively do anything,
+	// so I'm counting that as a Qt ignore.
+	if(event->key() == Qt::Key_F8) f8State = false;
+	if(event->key() == Qt::Key_F12) f12State = false;
+	event->ignore();
+}
+
 void ScanTargetWidget::keyPressEvent(QKeyEvent *event) {
-	// Use CTRL+Escape to end mouse captured mode, if currently captured; otherwise ignore the event.
-	// Empirical note: control actually appears to mean command on the Mac. I have no idea what the
-	// Mac's command key would actually be as a modifier. Fingers crossed control means control
-	// elsewhere (?).
-	if(mouseIsCaptured && event->key() == Qt::Key_Escape && event->modifiers()&Qt::ControlModifier) {
+	// Use either CTRL+Escape or F8+F12 to end mouse captured mode, if currently captured;
+	// otherwise ignore the event.
+
+	if(event->key() == Qt::Key_F8) f8State = true;
+	if(event->key() == Qt::Key_F12) f12State = true;
+
+	if(mouseIsCaptured && (
+		(event->key() == Qt::Key_Escape && event->modifiers()&Qt::ControlModifier) ||
+		(f8State && f12State)
+	)) {
 		releaseMouse();
 
 		QCursor cursor;

OSBindings/Qt/scantargetwidget.h

@@ -42,6 +42,7 @@ class ScanTargetWidget : public QOpenGLWidget {
 		void mouseReleaseEvent(QMouseEvent *) override;
 		void mouseMoveEvent(QMouseEvent *) override;
 		void keyPressEvent(QKeyEvent *) override;
+		void keyReleaseEvent(QKeyEvent *) override;
 
 		void releaseMouse();
 		void setMouseButtonPressed(Qt::MouseButton, bool);
@@ -66,6 +67,7 @@ class ScanTargetWidget : public QOpenGLWidget {
 
 		MouseDelegate *mouseDelegate = nullptr;
 		bool mouseIsCaptured = false;
+		bool f8State = false, f12State = false;	// To support F8+F12 as a mouse release combination.
 
 	private slots:
 		void vsync();

Outputs/CRT/CRT.cpp

@@ -27,7 +27,7 @@ void CRT::set_new_timing(int cycles_per_line, int height_of_display, Outputs::Di
 															//	7 microseconds for horizontal retrace and 500 to 750 microseconds for vertical retrace
 															//  in NTSC and PAL TV."
 
-	time_multiplier_ = 65535 / cycles_per_line;
+	time_multiplier_ = 63487 / cycles_per_line;	// 63475 = 65535 * 31/32, i.e. the same 1/32 error as below is permitted.
 	phase_denominator_ = int64_t(cycles_per_line) * int64_t(colour_cycle_denominator) * int64_t(time_multiplier_);
 	phase_numerator_ = 0;
 	colour_cycle_numerator_ = int64_t(colour_cycle_numerator);