Introduce one-directional FIFO.

Machines/Acorn/BBCMicro/BBCMicro.cpp

@@ -831,12 +831,12 @@ public:
 		}
 		adc_.run_for(duration);
 
-
 		if constexpr (has_1770) {
 			// The WD1770 is nominally clocked at 8Mhz.
 			wd1770_.run_for(duration * 4);
 		}
 
+
 		//
 		// Questionably-clocked devices.
 		//
@@ -943,6 +943,7 @@ public:
 			return duration;
 		}
 
+
 		//
 		// ROM or RAM access.
 		//

Machines/Acorn/Tube/FIFO.hpp

@@ -0,0 +1,37 @@
+//
+//  Header.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 30/10/2025.
+//  Copyright © 2025 Thomas Harte. All rights reserved.
+//
+
+#pragma once
+
+namespace Acorn::Tube {
+
+template <size_t length>
+struct FIFO {
+	uint8_t status() const {
+		return
+			((read != write) ? 0x80 : 0x00) |
+			((write - read < length) ? 0x40 : 0x00);
+	}
+
+	void write(const uint8_t value) {
+		if(write - read == length) return;
+		buffer[write++] = value;
+	}
+
+	void read() {
+		const uint8_t result = buffer[read];
+		if(write != read) ++read;
+	}
+
+private:
+	std::array<uint8_t, length> buffer;
+	uint32_t read = 0;
+	uint32_t write = 0;
+};
+
+}

Machines/Utility/ROMCatalogue.cpp

@@ -453,6 +453,14 @@ const std::vector<Description> &Description::all_roms() {
 			16_kb,
 			0x8314fed0u
 		},
+		{
+			BBCMicroTube110,
+			"BBCMicro",
+			"the Tube 1.10 Boot ROM",
+			"TUBE110.rom",
+			2_kb,
+			0x9ec2dbd0u
+		},
 
 	//
 	// ColecoVision.

Machines/Utility/ROMCatalogue.hpp

@@ -85,6 +85,7 @@ enum Name {
 	BBCMicroDFS226,
 	BBCMicroADFS130,
 	BBCMicroAdvancedDiscToolkit140,
+	BBCMicroTube110,
 
 	// ColecoVision.
 	ColecoVisionBIOS,

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

@@ -1612,6 +1612,7 @@
 		4B49F0A823346F7A0045E6A6 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = "Clock Signal/Base.lproj/MacintoshOptions.xib"; sourceTree = SOURCE_ROOT; };
 		4B4A75BC2EB2C55100EA398F /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/CompositeDynamicCropOptions.xib; sourceTree = "<group>"; };
 		4B4A75BF2EB399D700EA398F /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/DynamicCropOptions.xib; sourceTree = "<group>"; };
+		4B4A75C22EB43F1C00EA398F /* FIFO.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = FIFO.hpp; sourceTree = "<group>"; };
 		4B4A762E1DB1A3FA007AAE2E /* AY38910.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = AY38910.cpp; sourceTree = "<group>"; };
 		4B4A762F1DB1A3FA007AAE2E /* AY38910.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = AY38910.hpp; sourceTree = "<group>"; };
 		4B4B1A3A200198C900A0F866 /* KonamiSCC.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = KonamiSCC.cpp; sourceTree = "<group>"; };
@@ -3354,6 +3355,14 @@
 			path = uPD7002;
 			sourceTree = "<group>";
 		};
+		4B4A75C32EB43F1C00EA398F /* Tube */ = {
+			isa = PBXGroup;
+			children = (
+				4B4A75C22EB43F1C00EA398F /* FIFO.hpp */,
+			);
+			path = Tube;
+			sourceTree = "<group>";
+		};
 		4B4A762D1DB1A35C007AAE2E /* AY38910 */ = {
 			isa = PBXGroup;
 			children = (
@@ -4673,6 +4682,7 @@
 		4BB505682B962DDF0031C43C /* Acorn */ = {
 			isa = PBXGroup;
 			children = (
+				4B4A75C32EB43F1C00EA398F /* Tube */,
 				4BB505692B962DDF0031C43C /* Archimedes */,
 				4B710C8C2E77A3B20056BDF4 /* BBCMicro */,
 				4BB5056A2B962DDF0031C43C /* Electron */,

Outputs/CRT/CRT.cpp

@@ -113,20 +113,16 @@ void CRT::set_dynamic_framing(
 	float minimum_scale
 ) {
 	framing_ = Framing::Dynamic;
+	framing_bounds_ = initial;
 
-	dynamic_framer_.framing_bounds = initial;
-	dynamic_framer_.framing_bounds.scale(
-		maximum_scale / dynamic_framer_.framing_bounds.size.width,
-		maximum_scale / dynamic_framer_.framing_bounds.size.height
-	);
+	framing_bounds_ = initial;
+	framing_bounds_.scale(maximum_scale / framing_bounds_.size.width, maximum_scale / framing_bounds_.size.height);
 
-	dynamic_framer_.minimum_scale = minimum_scale;
-	dynamic_framer_.max_offsets[0] = max_centre_offset_x;
-	dynamic_framer_.max_offsets[1] = max_centre_offset_y;
+	minimum_scale_ = minimum_scale;
+	max_offsets_[0] = max_centre_offset_x;
+	max_offsets_[1] = max_centre_offset_y;
 
-	if(!has_first_reading_) {
-		previous_posted_rect_ = posted_rect_ = scan_target_modals_.visible_area = initial;
-	}
+	posted_rect_ = scan_target_modals_.visible_area = initial;
 	has_first_reading_ = true;
 }
 
@@ -139,10 +135,13 @@ void CRT::set_fixed_framing(const std::function<void()> &advance) {
 
 void CRT::set_fixed_framing(const Display::Rect frame) {
 	framing_ = Framing::Static;
-	static_frame_ = frame;
 	if(!has_first_reading_) {
 		scan_target_modals_.visible_area = frame;
 		scan_target_->set_modals(scan_target_modals_);
+	} else {
+		previous_posted_rect_ = posted_rect_;
+		posted_rect_ = frame;
+		animation_step_ = 0;
 	}
 }
 
@@ -294,7 +293,7 @@ void CRT::advance_cycles(
 		if(next_scan) {
 			next_scan->end_points[0] = end_point();
 			next_scan->composite_amplitude = colour_burst_amplitude_;
-		} else if(is_output_segment /* && is_calibrating(framing_) */) {
+		} else if(is_output_segment && is_calibrating(framing_)) {
 			start_point = end_point();
 		}
 
@@ -314,7 +313,7 @@ void CRT::advance_cycles(
 		vertical_flywheel_.apply_event(next_run_length, active_vertical_event);
 
 		if(active_vertical_event == Flywheel::SyncEvent::StartRetrace) {
-			/* if(is_calibrating(framing_)) */ {
+			if(is_calibrating(framing_)) {
 				active_rect_.origin.x /= scan_target_modals_.output_scale.x;
 				active_rect_.size.width /= scan_target_modals_.output_scale.x;
 				active_rect_.origin.y /= scan_target_modals_.output_scale.y;
@@ -342,7 +341,7 @@ void CRT::advance_cycles(
 			}
 			level_changes_in_frame_ = 0;
 
-			/* if(is_calibrating(framing_)) */ {
+			if(is_calibrating(framing_)) {
 				border_rect_ = active_rect_ = Display::Rect(65536.0f, 65536.0f, 0.0f, 0.0f);
 				captures_in_rect_ = 0;
 			}
@@ -359,9 +358,9 @@ void CRT::advance_cycles(
 
 		if(next_scan) {
 			next_scan->end_points[1] = end_point();
-			posit_scan(next_scan->end_points[0], next_scan->end_points[1]);
+			if(is_calibrating(framing_)) posit_scan(next_scan->end_points[0], next_scan->end_points[1]);
 			scan_target_->end_scan();
-		} else if(is_output_segment) {
+		} else if(is_output_segment && is_calibrating(framing_)) {
 			posit_scan(start_point, end_point());
 		}
 
@@ -471,22 +470,46 @@ void CRT::posit(Display::Rect rect) {
 	if(animation_step_ < AnimationSteps) {
 		set_rect(current_rect());
 		++animation_step_;
+
 		if(animation_step_ == AnimationSteps) {
 			previous_posted_rect_ = posted_rect_;
+
+			if(framing_ == Framing::CalibratingAutomaticFixed) {
+				framing_ =
+					border_rect_ != active_rect_ ?
+						Framing::BorderReactive : Framing::Static;
+				return;
+			}
 		}
 	}
 
+	// Static framing: don't further evaluate.
+	if(framing_ == Framing::Static) {
+		return;
+	}
+
 	// Zoom out very slightly if there's space; this avoids a cramped tight crop.
 	if(rect.size.width < 0.95 && rect.size.height < 0.95) {
 		rect.scale(1.02f, 1.02f);
 	}
 
-	std::optional<Display::Rect> first_reading;
+	// Border reactive: take frame as gospel.
+	if(framing_ == Framing::BorderReactive) {
+		if(rect != posted_rect_) {
+			previous_posted_rect_ = current_rect();
+			posted_rect_ = rect;
+			animation_step_ = 0;
+		}
+	}
+
 	if(!has_first_reading_) {
 		rect_accumulator_.posit(rect);
-		if(first_reading = rect_accumulator_.first_reading(); first_reading.has_value()) {
+
+		if(const auto reading = rect_accumulator_.first_reading(); reading.has_value()) {
+			previous_posted_rect_ = posted_rect_;
+			posted_rect_ = *reading;
+			animation_step_ = 0;
 			has_first_reading_ = true;
-#ifndef NDEBUG
 			Logger::info().append("First reading is (%0.5ff, %0.5ff, %0.5ff, %0.5ff)",
 				posted_rect_.origin.x, posted_rect_.origin.y,
 				posted_rect_.size.width, posted_rect_.size.height);
@@ -496,40 +519,24 @@ void CRT::posit(Display::Rect rect) {
 			Logger::info().append("90%% of whole frame was (%0.5ff, %0.5ff, %0.5ff, %0.5ff)",
 				frame.origin.x, frame.origin.y,
 				frame.size.width, frame.size.height);
-#endif
-
-			if(framing_ == Framing::CalibratingAutomaticFixed) {
-				static_frame_ = *first_reading;
-				framing_ =
-					border_rect_ != active_rect_ ?
-						Framing::BorderReactive : Framing::Static;
-				return;
-			}
 		}
+		return;
 	}
 
+	// Constrain to permitted bounds.
+	framing_bounds_.constrain(rect, max_offsets_[0], max_offsets_[1]);
+
+	// Constrain to minimum scale.
+	rect.scale(
+		rect.size.width > minimum_scale_ ? 1.0f : minimum_scale_ / rect.size.width,
+		rect.size.height > minimum_scale_ ? 1.0f : minimum_scale_ / rect.size.height
+	);
 
 	const auto output_frame = rect_accumulator_.posit(rect);
-	dynamic_framer_.update(rect, output_frame, first_reading);
-
-	const auto selected_rect = [&]() -> std::optional<Display::Rect> {
-		switch(framing_) {
-			default:						return rect;
-			case Framing::Static:			return static_frame_;
-			case Framing::Dynamic:			return dynamic_framer_.selection;
-		}
-	} ();
-
-	if(selected_rect && *selected_rect != posted_rect_) {
-		if(animation_step_ == NoFrameYet) {
-			animation_step_ = AnimationSteps;
-			previous_posted_rect_ = posted_rect_ = *selected_rect;
-			set_rect(posted_rect_);
-		} else {
-			previous_posted_rect_ = current_rect();
-			posted_rect_ = *selected_rect;
-			animation_step_ = 0;
-		}
+	if(output_frame && *output_frame != posted_rect_) {
+		previous_posted_rect_ = current_rect();
+		posted_rect_ = *output_frame;
+		animation_step_ = 0;
 	}
 }
 

Outputs/CRT/CRT.hpp

@@ -404,56 +404,31 @@ private:
 	Numeric::CubicCurve animation_curve_;
 
 	static constexpr int AnimationSteps = 100;
-	static constexpr int NoFrameYet = AnimationSteps + 1;
-	int animation_step_ = NoFrameYet;
+	int animation_step_ = AnimationSteps;
 
 	// Configured cropping options.
 	enum class Framing {
+		CalibratingAutomaticFixed,
 		Dynamic,
+
 		Static,
 		BorderReactive,
-
-		CalibratingAutomaticFixed,
 	};
+	static constexpr bool is_calibrating(const Framing framing) {
+		return framing < Framing::Static;
+	}
 
 	RectAccumulator rect_accumulator_;
-	struct DynamicFramer {
-		// Constraints.
-		Display::Rect framing_bounds;
-		float max_offsets[2]{};
-		float minimum_scale = 0.85f;
-
-		// Output.
-		std::optional<Display::Rect> selection;
-
-		// Logic.
-		void update(
-			Display::Rect rect,
-			const std::optional<Display::Rect> accumulated,
-			const std::optional<Display::Rect> first_reading
-		) {
-			// Constrain to permitted bounds.
-			framing_bounds.constrain(rect, max_offsets[0], max_offsets[1]);
-
-			// Constrain to minimum scale.
-			rect.scale(
-				rect.size.width > minimum_scale ? 1.0f : minimum_scale / rect.size.width,
-				rect.size.height > minimum_scale ? 1.0f : minimum_scale / rect.size.height
-			);
-
-			if(accumulated.has_value()) {
-				selection = accumulated;
-			} else if(first_reading.has_value()) {
-				selection = first_reading;
-			}
-		}
-	} dynamic_framer_;
-	std::optional<Display::Rect> static_frame_;
 
 	Framing framing_ = Framing::CalibratingAutomaticFixed;
 	bool has_first_reading_ = false;
 	void posit(Display::Rect);
 
+	// Affecting dynamic framing.
+	Outputs::Display::Rect framing_bounds_;
+	float minimum_scale_ = 0.85f;
+	float max_offsets_[2]{};
+
 #ifndef NDEBUG
 	size_t allocated_data_length_ = std::numeric_limits<size_t>::min();
 #endif