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317 lines
13 KiB
C++
317 lines
13 KiB
C++
//
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// CRT.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 19/07/2015.
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// Copyright © 2015 Thomas Harte. All rights reserved.
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//
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#ifndef CRT_hpp
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#define CRT_hpp
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#include <stdint.h>
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#include "CRTTypes.hpp"
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#include "Internals/Flywheel.hpp"
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#include "Internals/CRTOpenGL.hpp"
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#include "Internals/ArrayBuilder.hpp"
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#include "Internals/TextureBuilder.hpp"
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namespace Outputs {
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namespace CRT {
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class CRT;
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class Delegate {
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public:
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virtual void crt_did_end_batch_of_frames(CRT *crt, unsigned int number_of_frames, unsigned int number_of_unexpected_vertical_syncs) = 0;
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};
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class CRT {
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private:
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CRT(unsigned int common_output_divisor, unsigned int buffer_depth);
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// the incoming clock lengths will be multiplied by something to give at least 1000
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// sample points per line
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unsigned int time_multiplier_;
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const unsigned int common_output_divisor_;
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// the two flywheels regulating scanning
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std::unique_ptr<Flywheel> horizontal_flywheel_, vertical_flywheel_;
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uint16_t vertical_flywheel_output_divider_;
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// elements of sync separation
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bool is_receiving_sync_; // true if the CRT is currently receiving sync (i.e. this is for edge triggering of horizontal sync)
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int sync_capacitor_charge_level_; // this charges up during times of sync and depletes otherwise; needs to hit a required threshold to trigger a vertical sync
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int sync_capacitor_charge_threshold_; // this charges up during times of sync and depletes otherwise; needs to hit a required threshold to trigger a vertical sync
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unsigned int sync_period_;
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struct Scan {
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enum Type {
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Sync, Level, Data, Blank, ColourBurst
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} type;
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unsigned int number_of_cycles;
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union {
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struct {
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uint8_t phase, amplitude;
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};
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};
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};
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void output_scan(const Scan *scan);
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uint8_t colour_burst_phase_, colour_burst_amplitude_, colour_burst_phase_adjustment_;
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bool is_writing_composite_run_;
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unsigned int phase_denominator_, phase_numerator_, colour_cycle_numerator_;
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bool is_alernate_line_, phase_alternates_;
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// the outer entry point for dispatching output_sync, output_blank, output_level and output_data
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void advance_cycles(unsigned int number_of_cycles, bool hsync_requested, bool vsync_requested, const Scan::Type type);
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// the inner entry point that determines whether and when the next sync event will occur within
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// the current output window
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Flywheel::SyncEvent get_next_vertical_sync_event(bool vsync_is_requested, unsigned int cycles_to_run_for, unsigned int *cycles_advanced);
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Flywheel::SyncEvent get_next_horizontal_sync_event(bool hsync_is_requested, unsigned int cycles_to_run_for, unsigned int *cycles_advanced);
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// OpenGL state
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OpenGLOutputBuilder openGL_output_builder_;
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// temporary storage used during the construction of output runs
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struct {
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uint16_t x1, y;
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} output_run_;
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// the delegate
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Delegate *delegate_;
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unsigned int frames_since_last_delegate_call_;
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// queued tasks for the OpenGL queue; performed before the next draw
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std::mutex function_mutex_;
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std::vector<std::function<void(void)>> enqueued_openGL_functions_;
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inline void enqueue_openGL_function(const std::function<void(void)> &function) {
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std::lock_guard<std::mutex> function_guard(function_mutex_);
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enqueued_openGL_functions_.push_back(function);
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}
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// sync counter, for determining vertical sync
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unsigned int cycles_of_sync_;
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unsigned int cycles_since_sync_;
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unsigned int cycles_per_line_;
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public:
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/*! Constructs the CRT with a specified clock rate, height and colour subcarrier frequency.
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The requested number of buffers, each with the requested number of bytes per pixel,
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is created for the machine to write raw pixel data to.
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@param cycles_per_line The clock rate at which this CRT will be driven, specified as the number
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of cycles expected to take up one whole scanline of the display.
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@param common_output_divisor The greatest a priori common divisor of all cycle counts that will be
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supplied to @c output_sync, @c output_data, etc; supply 1 if no greater divisor is known. For many
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machines output will run at a fixed multiple of the clock rate; knowing this divisor can improve
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internal precision.
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@param height_of_display The number of lines that nominally form one field of the display, rounded
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up to the next whole integer.
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@param colour_cycle_numerator Specifies the numerator for the per-line frequency of the colour subcarrier.
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@param colour_cycle_denominator Specifies the denominator for the per-line frequency of the colour subcarrier.
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The colour subcarrier is taken to have colour_cycle_numerator/colour_cycle_denominator cycles per line.
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@param buffer_depth The depth per pixel of source data buffers to create for this machine. Machines
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may provide per-clock-cycle data in the depth that they consider convenient, supplying a sampling
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function to convert between their data format and either a composite or RGB signal, allowing that
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work to be offloaded onto the GPU and allowing the output signal to be sampled at a rate appropriate
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to the display size.
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@see @c set_rgb_sampling_function , @c set_composite_sampling_function
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*/
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CRT(unsigned int cycles_per_line, unsigned int common_output_divisor, unsigned int height_of_display, ColourSpace colour_space, unsigned int colour_cycle_numerator, unsigned int colour_cycle_denominator, bool should_alternate, unsigned int buffer_depth);
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/*! Constructs the CRT with the specified clock rate, with the display height and colour
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subcarrier frequency dictated by a standard display type and with the requested number of
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buffers, each with the requested number of bytes per pixel.
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Exactly identical to calling the designated constructor with colour subcarrier information
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looked up by display type.
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*/
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CRT(unsigned int cycles_per_line, unsigned int common_output_divisor, DisplayType displayType, unsigned int buffer_depth);
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/*! Resets the CRT with new timing information. The CRT then continues as though the new timing had
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been provided at construction. */
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void set_new_timing(unsigned int cycles_per_line, unsigned int height_of_display, ColourSpace colour_space, unsigned int colour_cycle_numerator, unsigned int colour_cycle_denominator, bool should_alternate);
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/*! Resets the CRT with new timing information derived from a new display type. The CRT then continues
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as though the new timing had been provided at construction. */
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void set_new_display_type(unsigned int cycles_per_line, DisplayType displayType);
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/*! Output at the sync level.
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@param number_of_cycles The amount of time to putput sync for.
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*/
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void output_sync(unsigned int number_of_cycles);
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/*! Output at the blanking level.
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@param number_of_cycles The amount of time to putput the blanking level for.
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*/
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void output_blank(unsigned int number_of_cycles);
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/*! Outputs the first written to the most-recently created run of data repeatedly for a prolonged period.
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@param number_of_cycles The number of cycles to repeat the output for.
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*/
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void output_level(unsigned int number_of_cycles);
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/*! Declares that the caller has created a run of data via @c allocate_write_area and @c get_write_target_for_buffer
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that is at least @c number_of_cycles long, and that the first @c number_of_cycles/source_divider should be spread
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over that amount of time.
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@param number_of_cycles The amount of data to output.
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@param source_divider A divider for source data; if the divider is 1 then one source pixel is output every cycle,
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if it is 2 then one source pixel covers two cycles; if it is n then one source pixel covers n cycles.
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@see @c allocate_write_area , @c get_write_target_for_buffer
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*/
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void output_data(unsigned int number_of_cycles, unsigned int source_divider);
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/*! Outputs a colour burst.
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@param number_of_cycles The length of the colour burst.
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@param phase The initial phase of the colour burst in a measuring system with 256 units
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per circle, e.g. 0 = 0 degrees, 128 = 180 degrees, 256 = 360 degree.
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@param amplitude The amplitude of the colour burst in 1/256ths of the amplitude of the
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positive portion of the wave.
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*/
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void output_colour_burst(unsigned int number_of_cycles, uint8_t phase, uint8_t amplitude = 102);
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/*! Outputs a colour burst exactly in phase with CRT expectations using the idiomatic amplitude.
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@param number_of_cycles The length of the colour burst;
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*/
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void output_default_colour_burst(unsigned int number_of_cycles);
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/*! Attempts to allocate the given number of output samples for writing.
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The beginning of the most recently allocated area is used as the start
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of data written by a call to @c output_data; it is acceptable to write and to
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output less data than the amount requested but that may be less efficient.
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Allocation should fail only if emulation is running significantly below real speed.
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@param required_length The number of samples to allocate.
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@returns A pointer to the allocated area if room is available; @c nullptr otherwise.
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*/
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inline uint8_t *allocate_write_area(size_t required_length) {
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std::unique_lock<std::mutex> output_lock = openGL_output_builder_.get_output_lock();
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return openGL_output_builder_.texture_builder.allocate_write_area(required_length);
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}
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/*! Causes appropriate OpenGL or OpenGL ES calls to be issued in order to draw the current CRT state.
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The caller is responsible for ensuring that a valid OpenGL context exists for the duration of this call.
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*/
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inline void draw_frame(unsigned int output_width, unsigned int output_height, bool only_if_dirty) {
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{
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std::lock_guard<std::mutex> function_guard(function_mutex_);
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for(std::function<void(void)> function : enqueued_openGL_functions_)
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{
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function();
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}
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enqueued_openGL_functions_.clear();
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}
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openGL_output_builder_.draw_frame(output_width, output_height, only_if_dirty);
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}
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/*! Tells the CRT that the next call to draw_frame will occur on a different OpenGL context than
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the previous.
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@param should_delete_resources If @c true then all resources — textures, vertex arrays, etc —
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currently held by the CRT will be deleted now via calls to glDeleteTexture and equivalent. If
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@c false then the references are simply marked as invalid.
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*/
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inline void set_openGL_context_will_change(bool should_delete_resources) {
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enqueue_openGL_function([should_delete_resources, this] {
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openGL_output_builder_.set_openGL_context_will_change(should_delete_resources);
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});
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}
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/*! Sets a function that will map from whatever data the machine provided to a composite signal.
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@param shader A GLSL fragment including a function with the signature
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`float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)`
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that evaluates to the composite signal level as a function of a source buffer, sampling location, colour
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carrier phase and amplitude.
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*/
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inline void set_composite_sampling_function(const std::string &shader) {
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enqueue_openGL_function([shader, this] {
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openGL_output_builder_.set_composite_sampling_function(shader);
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});
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}
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enum CompositeSourceType {
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/// The composite function provides continuous output.
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Continuous,
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/// The composite function provides discrete output with four unique values per colour cycle.
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DiscreteFourSamplesPerCycle
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};
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/*! Provides information about the type of output the composite sampling function provides — discrete or continuous.
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This is necessary because the CRT implementation samples discretely and therefore can use fewer intermediate
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samples if it can exactly duplicate the sampling rate and placement of the composite sampling function.
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A continuous function is assumed by default.
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@param type The type of output provided by the function supplied to `set_composite_sampling_function`.
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@param offset_of_first_sample The relative position within a full cycle of the colour subcarrier at which the
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first sample falls. E.g. 0.125 means "at 1/8th of the way through the complete cycle".
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*/
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void set_composite_function_type(CompositeSourceType type, float offset_of_first_sample = 0.0f);
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/*! Sets a function that will map from whatever data the machine provided to an RGB signal.
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If the output mode is composite then a default mapping from RGB to the display's composite
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format will be applied.
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@param shader A GLSL fragent including a function with the signature
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`vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)` that evaluates to an RGB colour
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as a function of:
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* `usampler2D sampler` representing the source buffer;
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* `vec2 coordinate` representing the source buffer location to sample from in the range [0, 1); and
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* `vec2 icoordinate` representing the source buffer location to sample from as a pixel count, for easier multiple-pixels-per-byte unpacking.
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*/
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inline void set_rgb_sampling_function(const std::string &shader) {
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enqueue_openGL_function([shader, this] {
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openGL_output_builder_.set_rgb_sampling_function(shader);
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});
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}
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inline void set_output_device(OutputDevice output_device) {
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enqueue_openGL_function([output_device, this] {
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openGL_output_builder_.set_output_device(output_device);
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});
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}
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inline void set_visible_area(Rect visible_area) {
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enqueue_openGL_function([visible_area, this] {
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openGL_output_builder_.set_visible_area(visible_area);
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});
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}
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Rect 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);
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inline void set_delegate(Delegate *delegate) {
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delegate_ = delegate;
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}
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};
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}
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}
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#endif /* CRT_cpp */
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