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CLK/Machines/ZX8081/Video.cpp
Thomas Harte 6547560e52 Gives the CRT the ability to move iCoordinate multiplication outside of the fragment loop.
That resolves precision issues, as were plaguing the Apple II.
2018-04-18 19:29:03 -04:00

118 lines
3.5 KiB
C++

//
// Video.cpp
// Clock Signal
//
// Created by Thomas Harte on 06/06/2017.
// Copyright © 2017 Thomas Harte. All rights reserved.
//
#include "Video.hpp"
using namespace ZX8081;
namespace {
/*!
The number of bytes of PCM data to allocate at once; if/when more are required,
the class will simply allocate another batch.
*/
const std::size_t StandardAllocationSize = 40;
/// The amount of time a byte takes to output.
const std::size_t HalfCyclesPerByte = 8;
}
Video::Video() :
crt_(new Outputs::CRT::CRT(207 * 2, 1, Outputs::CRT::DisplayType::PAL50, 1)) {
// Set a composite sampling function that assumes 1bpp input.
crt_->set_composite_sampling_function(
"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
"{"
"uint texValue = texture(sampler, coordinate).r;"
"texValue <<= int(icoordinate.x) & 7;"
"return float(texValue & 128u);"
"}");
crt_->set_integer_coordinate_multiplier(8.0f);
// Show only the centre 80% of the TV frame.
crt_->set_video_signal(Outputs::CRT::VideoSignal::Composite);
crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.1f, 0.8f, 0.8f));
}
void Video::run_for(const HalfCycles half_cycles) {
// Just keep a running total of the amount of time that remains owed to the CRT.
cycles_since_update_ += static_cast<unsigned int>(half_cycles.as_int());
}
void Video::flush() {
flush(sync_);
}
void Video::flush(bool next_sync) {
if(sync_) {
// If in sync, that takes priority. Output the proper amount of sync.
crt_->output_sync(cycles_since_update_);
} else {
// If not presently in sync, then...
if(line_data_) {
// If there is output data queued, output it either if it's being interrupted by
// sync, or if we're past its end anyway. Otherwise let it be.
unsigned int data_length = static_cast<unsigned int>(line_data_pointer_ - line_data_) * HalfCyclesPerByte;
if(data_length < cycles_since_update_ || next_sync) {
unsigned int output_length = std::min(data_length, cycles_since_update_);
crt_->output_data(output_length, output_length / HalfCyclesPerByte);
line_data_pointer_ = line_data_ = nullptr;
cycles_since_update_ -= output_length;
} else return;
}
// Any pending pixels being dealt with, pad with the white level.
uint8_t *colour_pointer = static_cast<uint8_t *>(crt_->allocate_write_area(1));
if(colour_pointer) *colour_pointer = 0xff;
crt_->output_level(cycles_since_update_);
}
cycles_since_update_ = 0;
}
void Video::set_sync(bool sync) {
// Do nothing if sync hasn't changed.
if(sync_ == sync) return;
// Complete whatever was being drawn, and update sync.
flush(sync);
sync_ = sync;
}
void Video::output_byte(uint8_t byte) {
// Complete whatever was going on.
if(sync_) return;
flush();
// Grab a buffer if one isn't already available.
if(!line_data_) {
line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
}
// If a buffer was obtained, serialise the new pixels.
if(line_data_) {
// If the buffer is full, output it now and obtain a new one
if(line_data_pointer_ - line_data_ == StandardAllocationSize) {
crt_->output_data(StandardAllocationSize * HalfCyclesPerByte, StandardAllocationSize);
cycles_since_update_ -= StandardAllocationSize * HalfCyclesPerByte;
line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
if(!line_data_) return;
}
line_data_pointer_[0] = byte;
line_data_pointer_ ++;
}
}
Outputs::CRT::CRT *Video::get_crt() {
return crt_.get();
}