Sought to shift locking back up to the CRT. And to be a bit more RAII-ish.

Outputs/CRT/CRT.cpp

@@ -110,6 +110,7 @@ Flywheel::SyncEvent CRT::get_next_horizontal_sync_event(bool hsync_is_requested,
 
 void CRT::advance_cycles(unsigned int number_of_cycles, unsigned int source_divider, bool hsync_requested, bool vsync_requested, const bool vsync_charging, const Scan::Type type, uint16_t tex_x, uint16_t tex_y)
 {
+	std::unique_lock<std::mutex> output_lock = openGL_output_builder_.get_output_lock();
 	number_of_cycles *= time_multiplier_;
 
 	bool is_output_run = ((type == Scan::Type::Level) || (type == Scan::Type::Data));
@@ -189,8 +190,6 @@ void CRT::advance_cycles(unsigned int number_of_cycles, unsigned int source_divi
 				}
 				else
 				{
-					openGL_output_builder_.lock_output();
-
 					// Get and write all those previously unwritten output ys
 					const uint16_t output_y = openGL_output_builder_.get_composite_output_y();
 
@@ -221,8 +220,6 @@ void CRT::advance_cycles(unsigned int number_of_cycles, unsigned int source_divi
 								(*(uint16_t *)&input_buffer[position + SourceVertexOffsetOfOutputStart + 2]) = output_y;
 							}
 						});
-
-					openGL_output_builder_.unlock_output();
 				}
 				is_writing_composite_run_ ^= true;
 			}
@@ -320,24 +317,11 @@ void CRT::output_blank(unsigned int number_of_cycles)
 
 void CRT::output_level(unsigned int number_of_cycles)
 {
-	if(!openGL_output_builder_.array_builder.is_full())
-	{
-		Scan scan {
-			.type = Scan::Type::Level,
-			.number_of_cycles = number_of_cycles,
-//			.tex_x = openGL_output_builder_.texture_builder.get_last_write_x_position(),
-//			.tex_y = openGL_output_builder_.texture_builder.get_last_write_y_position()
-		};
-		output_scan(&scan);
-	}
-	else
-	{
-		Scan scan {
-			.type = Scan::Type::Blank,
-			.number_of_cycles = number_of_cycles
-		};
-		output_scan(&scan);
-	}
+	Scan scan {
+		.type = Scan::Type::Level,
+		.number_of_cycles = number_of_cycles,
+	};
+	output_scan(&scan);
 }
 
 void CRT::output_colour_burst(unsigned int number_of_cycles, uint8_t phase, uint8_t amplitude)
@@ -353,26 +337,13 @@ void CRT::output_colour_burst(unsigned int number_of_cycles, uint8_t phase, uint
 
 void CRT::output_data(unsigned int number_of_cycles, unsigned int source_divider)
 {
-	if(!openGL_output_builder_.array_builder.is_full())
-	{
-		openGL_output_builder_.texture_builder.reduce_previous_allocation_to(number_of_cycles / source_divider);
-		Scan scan {
-			.type = Scan::Type::Data,
-			.number_of_cycles = number_of_cycles,
-//			.tex_x = openGL_output_builder_.texture_builder.get_last_write_x_position(),
-//			.tex_y = openGL_output_builder_.texture_builder.get_last_write_y_position(),
-			.source_divider = source_divider
-		};
-		output_scan(&scan);
-	}
-	else
-	{
-		Scan scan {
-			.type = Scan::Type::Blank,
-			.number_of_cycles = number_of_cycles
-		};
-		output_scan(&scan);
-	}
+	openGL_output_builder_.texture_builder.reduce_previous_allocation_to(number_of_cycles / source_divider);
+	Scan scan {
+		.type = Scan::Type::Data,
+		.number_of_cycles = number_of_cycles,
+		.source_divider = source_divider
+	};
+	output_scan(&scan);
 }
 
 Outputs::CRT::Rect CRT::get_rect_for_area(int first_line_after_sync, int number_of_lines, int first_cycle_after_sync, int number_of_cycles, float aspect_ratio)

Outputs/CRT/CRT.hpp

@@ -192,6 +192,7 @@ class CRT {
 		*/
 		inline uint8_t *allocate_write_area(size_t required_length)
 		{
+			std::unique_lock<std::mutex> output_lock = openGL_output_builder_.get_output_lock();
 			return openGL_output_builder_.texture_builder.allocate_write_area(required_length);
 		}
 

Outputs/CRT/Internals/ArrayBuilder.cpp

@@ -23,7 +23,6 @@ ArrayBuilder::ArrayBuilder(size_t input_size, size_t output_size, std::function<
 bool ArrayBuilder::is_full()
 {
 	bool was_full;
-	std::lock_guard<std::mutex> guard(buffer_mutex_);
 	was_full = is_full_;
 	return was_full;
 }
@@ -40,7 +39,6 @@ uint8_t *ArrayBuilder::get_output_storage(size_t size)
 
 void ArrayBuilder::flush(const std::function<void(uint8_t *input, size_t input_size, uint8_t *output, size_t output_size)> &function)
 {
-	std::lock_guard<std::mutex> guard(buffer_mutex_);
 	if(!is_full_)
 	{
 		size_t input_size, output_size;
@@ -67,7 +65,6 @@ ArrayBuilder::Submission ArrayBuilder::submit()
 {
 	ArrayBuilder::Submission submission;
 
-	std::lock_guard<std::mutex> guard(buffer_mutex_);
 	submission.input_size = input_.submit(true);
 	submission.output_size = output_.submit(false);
 	if(is_full_)
@@ -102,7 +99,6 @@ ArrayBuilder::Buffer::~Buffer()
 
 uint8_t *ArrayBuilder::get_storage(size_t size, Buffer &buffer)
 {
-	std::lock_guard<std::mutex> guard(buffer_mutex_);
 	uint8_t *pointer = buffer.get_storage(size);
 	if(!pointer) is_full_ = true;
 	return pointer;

Outputs/CRT/Internals/ArrayBuilder.hpp

@@ -9,9 +9,9 @@
 #ifndef ArrayBuilder_hpp
 #define ArrayBuilder_hpp
 
-#include <vector>
-#include <mutex>
+#include <functional>
 #include <memory>
+#include <vector>
 
 #include "OpenGL.hpp"
 
@@ -92,7 +92,6 @@ class ArrayBuilder {
 		} output_, input_;
 		uint8_t *get_storage(size_t size, Buffer &buffer);
 
-		std::mutex buffer_mutex_;
 		bool is_full_;
 };
 

Outputs/CRT/Internals/CRTOpenGL.hpp

@@ -90,6 +90,7 @@ class OpenGLOutputBuilder {
 		GLsync fence_;
 
 	public:
+		// These two are protected by output_mutex_.
 		TextureBuilder texture_builder;
 		ArrayBuilder array_builder;
 
@@ -98,12 +99,11 @@ class OpenGLOutputBuilder {
 
 		inline void set_colour_format(ColourSpace colour_space, unsigned int colour_cycle_numerator, unsigned int colour_cycle_denominator)
 		{
-			output_mutex_.lock();
+			std::lock_guard<std::mutex> output_guard(output_mutex_);
 			colour_space_ = colour_space;
 			colour_cycle_numerator_ = colour_cycle_numerator;
 			colour_cycle_denominator_ = colour_cycle_denominator;
 			set_colour_space_uniforms();
-			output_mutex_.unlock();
 		}
 
 		inline void set_visible_area(Rect visible_area)
@@ -111,14 +111,9 @@ class OpenGLOutputBuilder {
 			visible_area_ = visible_area;
 		}
 
-		inline void lock_output()
+		inline std::unique_lock<std::mutex> get_output_lock()
 		{
-			output_mutex_.lock();
-		}
-
-		inline void unlock_output()
-		{
-			output_mutex_.unlock();
+			return std::unique_lock<std::mutex>(output_mutex_);
 		}
 
 		inline OutputDevice get_output_device()