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179 lines
5.3 KiB
C++
179 lines
5.3 KiB
C++
//
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// ScanTarget.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/11/2018.
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// Copyright © 2018 Thomas Harte. All rights reserved.
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//
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#ifndef ScanTarget_hpp
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#define ScanTarget_hpp
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#include "../ScanTarget.hpp"
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#include "OpenGL.hpp"
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#include "Primitives/TextureTarget.hpp"
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#include "Primitives/Rectangle.hpp"
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#include <array>
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#include <atomic>
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#include <cstdint>
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#include <string>
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#include <vector>
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namespace Outputs {
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namespace Display {
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namespace OpenGL {
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/*!
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Provides a ScanTarget that uses OpenGL to render its output;
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this uses various internal buffers so that the only geometry
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drawn to the target framebuffer is a quad.
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*/
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class ScanTarget: public Outputs::Display::ScanTarget {
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public:
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ScanTarget();
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~ScanTarget();
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void draw(bool synchronous, int output_width, int output_height);
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private:
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static constexpr int WriteAreaWidth = 2048;
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static constexpr int WriteAreaHeight = 2048;
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static constexpr int LineBufferWidth = 2048;
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static constexpr int LineBufferHeight = 2048;
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// Outputs::Display::ScanTarget overrides.
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void set_modals(Modals) override;
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Scan *begin_scan() override;
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void end_scan() override;
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uint8_t *begin_data(size_t required_length, size_t required_alignment) override;
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void end_data(size_t actual_length) override;
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void submit() override;
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void announce(Event event, uint16_t x, uint16_t y) override;
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// Extends the definition of a Scan to include two extra fields,
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// relevant to the way that this scan target processes video.
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struct Scan {
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Outputs::Display::ScanTarget::Scan scan;
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/// Stores the y coordinate that this scan's data is at, within the write area texture.
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uint16_t data_y;
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/// Stores the y coordinate of this scan within the line buffer.
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uint16_t line;
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};
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struct PointerSet {
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// The sizes below might be less hassle as something more natural like ints,
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// but squeezing this struct into 64 bits makes the std::atomics more likely
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// to be lock free; they are under LLVM x86-64.
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int write_area = 0;
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uint16_t scan_buffer = 0;
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uint16_t line = 0;
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};
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/// A pointer to the next thing that should be provided to the caller for data.
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PointerSet write_pointers_;
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/// A pointer to the final thing currently cleared for submission.
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std::atomic<PointerSet> submit_pointers_;
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/// A pointer to the first thing not yet submitted for display.
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std::atomic<PointerSet> read_pointers_;
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// Maintains a buffer of the most recent 3072 scans.
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std::array<Scan, 3072> scan_buffer_;
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// Maintains a list of composite scan buffer coordinates; the Line struct
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// is transported to the GPU in its entirety; the LineMetadatas live in CPU
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// space only.
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struct Line {
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struct EndPoint {
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uint16_t x, y;
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} end_points[2];
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uint16_t line;
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};
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struct LineMetadata {
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bool is_first_in_frame;
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};
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std::array<Line, LineBufferHeight> line_buffer_;
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std::array<LineMetadata, LineBufferHeight> line_metadata_buffer_;
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// Contains the first composition of scans into lines;
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// they're accumulated prior to output to allow for continuous
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// application of any necessary conversions — e.g. composite processing.
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TextureTarget unprocessed_line_texture_;
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// Scans are accumulated to the accumulation texture; the full-display
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// rectangle is used to ensure untouched pixels properly decay.
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std::unique_ptr<TextureTarget> accumulation_texture_;
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Rectangle full_display_rectangle_;
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// Ephemeral state that helps in line composition.
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Line *active_line_ = nullptr;
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int provided_scans_ = 0;
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bool is_first_in_frame_ = true;
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// OpenGL storage handles for buffer data.
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GLuint scan_buffer_name_ = 0, scan_vertex_array_ = 0;
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GLuint line_buffer_name_ = 0, line_vertex_array_ = 0;
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template <typename T> void allocate_buffer(const T &array, GLuint &buffer_name, GLuint &vertex_array_name);
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template <typename T> void patch_buffer(const T &array, GLuint target, uint16_t submit_pointer, uint16_t read_pointer);
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// Uses a texture to vend write areas.
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std::vector<uint8_t> write_area_texture_;
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size_t data_type_size_ = 0;
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GLuint write_area_texture_name_ = 0;
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bool texture_exists_ = false;
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// Ephemeral information for the begin/end functions.
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Scan *vended_scan_ = nullptr;
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int vended_write_area_pointer_ = 0;
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// Track allocation failures.
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bool allocation_has_failed_ = false;
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// Receives scan target modals.
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Modals modals_;
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enum class ShaderType {
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Scan,
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Line
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};
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/*!
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@returns A string containing GLSL code describing the standard set of
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@c in and @c uniform variables to bind to the relevant struct
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from [...]OpenGL::ScanTarget and a vertex function to provide
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the standard varyings.
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*/
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static std::string glsl_globals(ShaderType type);
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/*!
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*/
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static std::string glsl_default_vertex_shader(ShaderType type);
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/*!
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Calls @c taret.enable_vertex_attribute_with_pointer to attach all
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globals for shaders of @c type to @c target.
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*/
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void enable_vertex_attributes(ShaderType type, Shader &target);
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void set_uniforms(ShaderType type, Shader &target);
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GLsync fence_ = nullptr;
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std::atomic_flag is_drawing_;
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int processing_width_ = 0;
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std::unique_ptr<Shader> input_shader_;
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std::unique_ptr<Shader> output_shader_;
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static std::unique_ptr<Shader> input_shader(InputDataType input_data_type, OutputType output_type);
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};
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}
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}
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}
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#endif /* ScanTarget_hpp */
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