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256 lines
11 KiB
C++
256 lines
11 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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namespace Outputs {
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namespace CRT {
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class CRT {
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private:
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CRT(unsigned int common_output_divisor);
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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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// fundamental creator-specified properties
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unsigned int _cycles_per_line;
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unsigned int _height_of_display;
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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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// each call to output_* generates a scan. A two-slot queue for scans allows edge extensions.
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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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unsigned int source_divider;
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uint16_t tex_x, tex_y;
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};
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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;
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uint16_t _colour_burst_time;
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bool _is_writing_composite_run;
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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, 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);
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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, kept behind an opaque pointer to avoid inclusion of the GL headers here.
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std::unique_ptr<OpenGLOutputBuilder> _openGL_output_builder;
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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_dispaly 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, 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);
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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);
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/*! Ensures that the given number of output samples are allocated 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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@param required_length The number of samples to allocate.
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@returns A pointer to the allocated area.
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*/
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inline uint8_t *allocate_write_area(size_t required_length)
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{
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return _openGL_output_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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_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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{
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_openGL_output_builder->set_openGL_context_will_change(should_delete_resources);
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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(vec2 coordinate, float phase)` that evaluates to the composite signal
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level as a function of a source buffer sampling location and the provided colour carrier phase.
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The shader may assume a uniform array of sampler2Ds named `buffers` provides access to all input data.
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*/
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inline void set_composite_sampling_function(const char *shader)
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{
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_openGL_output_builder->set_composite_sampling_function(shader);
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}
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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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`vec4 rgb_sample(vec2 coordinate)` that evaluates to an RGBA colour as a function of
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the source buffer sampling location.
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The shader may assume a uniform array of sampler2Ds named `buffers` provides access to all input data.
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*/
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inline void set_rgb_sampling_function(const char *shader)
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{
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_openGL_output_builder->set_rgb_sampling_function(shader);
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}
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/*! Optionally sets a function that will map from an input cycle count to a colour carrier phase.
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If this function is not supplied then the colour phase is determined from
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the input clock rate and the the colour cycle clock rate. Machines whose per-line clock rate
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is not intended exactly to match the normal line time may prefer to supply a custom function.
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@param A GLSL fragent including a function with the signature
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`float phase_for_clock_cycle(int cycle)` that returns the colour phase at the beginning of
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the supplied cycle.
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*/
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// void set_phase_function(const char *shader);
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inline void set_output_device(OutputDevice output_device)
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{
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_openGL_output_builder->set_output_device(output_device);
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}
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inline void set_visible_area(Rect visible_area)
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{
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_openGL_output_builder->set_visible_area(visible_area);
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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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