Eliminate LineMetadata, redundant memory barriers.

Outputs/OpenGL/ScanTarget.cpp

@@ -84,7 +84,7 @@ ScanTarget::ScanTarget(const API api, const GLuint target_framebuffer, const flo
 	dirty_zones_(dirty_zones_buffer_) {
 
 	set_scan_buffer(scan_buffer_.data(), scan_buffer_.size());
-	set_line_buffer(line_buffer_.data(), line_metadata_buffer_.data(), line_buffer_.size());
+	set_line_buffer(line_buffer_.data(), line_buffer_.size());
 
 	// TODO: if this is OpenGL 4.4 or newer, use glBufferStorage rather than glBufferData
 	// and specify GL_MAP_PERSISTENT_BIT. Then map the buffer now, and let the client

Outputs/OpenGL/ScanTarget.hpp

@@ -99,7 +99,6 @@ private:
 	std::vector<uint8_t> write_area_texture_;
 	std::array<Scan, LineBufferHeight*5> scan_buffer_{};
 	std::array<Line, LineBufferHeight> line_buffer_{};
-	std::array<LineMetadata, LineBufferHeight> line_metadata_buffer_{};
 	std::array<DirtyZone, 2> dirty_zones_buffer_{};
 
 	VertexArray scans_;

Outputs/ScanTargets/BufferingScanTarget.cpp

@@ -264,19 +264,7 @@ void BufferingScanTarget::announce(
 	} else {
 		// Commit the most recent line only if any scans fell on it and all allocation was successful.
 		if(!allocation_has_failed_ && provided_scans_) {
-			const auto submit_pointers = submit_pointers_.load(std::memory_order_relaxed);
-
-			// Store metadata.
-			LineMetadata &metadata = line_metadata_buffer_[size_t(write_pointers_.line)];
-			metadata.is_first_in_frame = is_first_in_frame_;
-			metadata.previous_frame_was_complete = previous_frame_was_complete_;
-			metadata.first_scan = submit_pointers.scan;
-			is_first_in_frame_ = false;
-
-			// Sanity check.
-			assert(((metadata.first_scan + size_t(provided_scans_)) % scan_buffer_size_) == write_pointers_.scan);
-
-			// Store actual line data.
+			// Store line data.
 			Line &active_line = line_buffer_[size_t(write_pointers_.line)];
 			active_line.end_points[1].x = location.x;
 			active_line.end_points[1].y = location.y;
@@ -287,7 +275,6 @@ void BufferingScanTarget::announce(
 			write_pointers_.line = uint16_t((write_pointers_.line + 1) % line_buffer_size_);
 
 			// Update the submit pointers with all lines, scans and data written during this line.
-			std::atomic_thread_fence(std::memory_order_release);
 			submit_pointers_.store(write_pointers_, std::memory_order_release);
 		} else {
 			// Something failed, or there was nothing on the line anyway, so reset all pointers to where they
@@ -344,7 +331,6 @@ BufferingScanTarget::OutputArea BufferingScanTarget::get_output_area() {
 	const auto read_ahead_pointers = read_ahead_pointers_.load(std::memory_order_relaxed);
 	const auto frame_read = frame_read_.load(std::memory_order_relaxed);
 	const auto frame_write = frame_write_.load(std::memory_order_relaxed);
-	std::atomic_thread_fence(std::memory_order_acquire);
 
 	OutputArea area;
 
@@ -397,11 +383,9 @@ void BufferingScanTarget::set_scan_buffer(Scan *const buffer, const size_t size)
 
 void BufferingScanTarget::set_line_buffer(
 	Line *const line_buffer,
-	LineMetadata *const metadata_buffer,
 	const size_t size
 ) {
 	line_buffer_ = line_buffer;
-	line_metadata_buffer_ = metadata_buffer;
 	line_buffer_size_ = size;
 }
 

Outputs/ScanTargets/BufferingScanTarget.hpp

@@ -94,7 +94,7 @@ public:
 	void set_scan_buffer(Scan *buffer, size_t size);
 
 	/// Sets the area of memory to use as line and line metadata buffers.
-	void set_line_buffer(Line *line_buffer, LineMetadata *metadata_buffer, size_t size);
+	void set_line_buffer(Line *line_buffer, size_t size);
 
 	/// Sets a new base address for the texture.
 	/// When called this will flush all existing data and load up the
@@ -282,7 +282,6 @@ private:
 
 	// The owner-supplied line buffer and size.
 	Line *line_buffer_ = nullptr;
-	LineMetadata *line_metadata_buffer_ = nullptr;
 	size_t line_buffer_size_ = 0;
 
 	// Current modals and whether they've yet been returned