CLK/Machines/Oric/Video.cpp

//
//  Video.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 12/10/2016.
//  Copyright 2016 Thomas Harte. All rights reserved.
//

#include "Video.hpp"

#include <algorithm>

//#define SUPPLY_COMPOSITE

using namespace Oric;

namespace {
	const unsigned int PAL50VSyncStartPosition = 256*64;
	const unsigned int PAL60VSyncStartPosition = 234*64;
	const unsigned int PAL50VSyncEndPosition = 260*64;
	const unsigned int PAL60VSyncEndPosition = 238*64;
	const unsigned int PAL50Period = 312*64;
	const unsigned int PAL60Period = 264*64;
}

VideoOutput::VideoOutput(uint8_t *memory) :
		ram_(memory),
		crt_(64*6, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red1Green1Blue1),
		frequency_mismatch_warner_(*this),
		v_sync_start_position_(PAL50VSyncStartPosition), v_sync_end_position_(PAL50VSyncEndPosition),
		counter_period_(PAL50Period) {
	crt_.set_phase_linked_luminance_offset(-1.0f / 8.0f);
	data_type_ = Outputs::Display::InputDataType::Red1Green1Blue1;
	crt_.set_input_data_type(data_type_);
	crt_.set_delegate(&frequency_mismatch_warner_);
	update_crt_frequency();
}

void VideoOutput::register_crt_frequency_mismatch() {
	crt_is_60Hz_ ^= true;
	update_crt_frequency();
}

void VideoOutput::update_crt_frequency() {
	// Set the proper frequency...
	crt_.set_new_display_type(64*6, crt_is_60Hz_ ? Outputs::Display::Type::PAL60 : Outputs::Display::Type::PAL50);

	// ... but also pick an appropriate crop rectangle.
	crt_.set_visible_area(crt_.get_rect_for_area(crt_is_60Hz_ ? 26 : 54, 224, 16 * 6, 40 * 6, 4.0f / 3.0f));
}

void VideoOutput::set_display_type(Outputs::Display::DisplayType display_type) {
	crt_.set_display_type(display_type);

#ifdef SUPPLY_COMPOSITE
	const auto data_type =
		(!has_colour_rom_ || display_type == Outputs::Display::DisplayType::RGB) ?
			Outputs::Display::InputDataType::Red1Green1Blue1 :
			Outputs::Display::InputDataType::PhaseLinkedLuminance8;
#else
	const auto data_type = Outputs::Display::InputDataType::Red1Green1Blue1;
#endif

	if(data_type_ != data_type) {
		data_type_ = data_type;
		crt_.set_input_data_type(data_type_);
	}
}

Outputs::Display::DisplayType VideoOutput::get_display_type() const {
	return crt_.get_display_type();
}

void VideoOutput::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
	crt_.set_scan_target(scan_target);
}

Outputs::Display::ScanStatus VideoOutput::get_scaled_scan_status() const {
	return crt_.get_scaled_scan_status() / 6.0f;
}

void VideoOutput::set_colour_rom(const std::vector<uint8_t> &rom) {
	has_colour_rom_ = true;
	for(std::size_t c = 0; c < 8; c++) {
		colour_forms_[c] = 0;

		uint8_t *const colour = reinterpret_cast<uint8_t *>(&colour_forms_[c]);
		const std::size_t index = (c << 2);

		// Values in the ROM are encoded for indexing by two square waves
		// in quadrature, which means that they're indexed in the order
		// 0, 1, 3, 2.
		colour[0] = uint8_t((rom[index] & 0x0f) << 4);
		colour[1] = uint8_t(rom[index] & 0xf0);
		colour[2] = uint8_t(rom[index+1] & 0xf0);
		colour[3] = uint8_t((rom[index+1] & 0x0f) << 4);

		// Extracting just the visible part of the stored range of values
		// means extracting the range 0x40 to 0xe0.
		for(int sub = 0; sub < 4; ++sub) {
			colour[sub] = ((colour[sub] - 0x40) * 255) / 0xa0;
		}
	}

	// Check for big endianness and byte swap if required.
//	uint32_t test_value = 0x0001;
//	if(*reinterpret_cast<uint8_t *>(&test_value) != 0x01) {
//		for(std::size_t c = 0; c < 8; c++) {
//			colour_forms_[c] = uint16_t((colour_forms_[c] >> 8) | (colour_forms_[c] << 8));
//		}
//	}
}

bool VideoOutput::vsync() {
	return counter_ >= v_sync_start_position_ && counter_ < v_sync_end_position_;
}

Cycles VideoOutput::next_sequence_point() const {
	if(counter_ < v_sync_start_position_) {
		return Cycles(v_sync_start_position_ - counter_);
	} else if(counter_ < v_sync_end_position_) {
		return Cycles(v_sync_end_position_ - counter_);
	} else {
		// After vsync the length of the next frame is baked in, so this is safe
		// (but should probably be factored out).
		return Cycles(
			counter_period_ + static_cast<int>(next_frame_is_sixty_hertz_ ? PAL60VSyncStartPosition : PAL50VSyncStartPosition)
			- counter_
		);
	}
}

void VideoOutput::run_for(const Cycles cycles) {
	// Horizontal: 0-39: pixels; otherwise blank; 48-53 sync, 54-56 colour burst.
	// Vertical: 0-223: pixels; otherwise blank; 256-259 (50Hz) or 234-238 (60Hz) sync.

#define clamp(action)	\
	if(cycles_run_for <= number_of_cycles) { action; } else cycles_run_for = number_of_cycles;

	int number_of_cycles = int(cycles.as_integral());
	while(number_of_cycles) {
		int h_counter = counter_ & 63;
		int cycles_run_for = 0;

		if(vsync()) {
			// this is a sync line
			cycles_run_for = v_sync_end_position_ - counter_;
			clamp(crt_.output_sync((v_sync_end_position_ - v_sync_start_position_) * 6));
		} else if(counter_ < 224*64 && h_counter < 40) {
			// this is a pixel line
			if(!h_counter) {
				ink_ = 0x7;
				paper_ = 0x0;
				use_alternative_character_set_ = use_double_height_characters_ = blink_text_ = false;
				set_character_set_base_address();

				if(data_type_ == Outputs::Display::InputDataType::Red1Green1Blue1) {
					rgb_pixel_target_ = reinterpret_cast<uint8_t *>(crt_.begin_data(240));
				} else {
					composite_pixel_target_ = reinterpret_cast<uint32_t *>(crt_.begin_data(240));
				}

				if(!counter_) {
					frame_counter_++;

					v_sync_start_position_ = next_frame_is_sixty_hertz_ ? PAL60VSyncStartPosition : PAL50VSyncStartPosition;
					v_sync_end_position_ = next_frame_is_sixty_hertz_ ? PAL60VSyncEndPosition : PAL50VSyncEndPosition;
					counter_period_ = next_frame_is_sixty_hertz_ ? PAL60Period : PAL50Period;
				}
			}

			cycles_run_for = std::min(40 - h_counter, number_of_cycles);
			int columns = cycles_run_for;
			int pixel_base_address = 0xa000 + (counter_ >> 6) * 40;
			int character_base_address = 0xbb80 + (counter_ >> 9) * 40;
			const uint8_t blink_mask = (blink_text_ && (frame_counter_&32)) ? 0x00 : 0xff;

			while(columns--) {
				uint8_t pixels, control_byte;

				if(is_graphics_mode_ && counter_ < 200*64) {
					control_byte = pixels = ram_[pixel_base_address + h_counter];
				} else {
					int address = character_base_address + h_counter;
					control_byte = ram_[address];
					const int line = use_double_height_characters_ ? ((counter_ >> 7) & 7) : ((counter_ >> 6) & 7);
					pixels = ram_[character_set_base_address_ + (control_byte&127) * 8 + line];
				}

				const uint8_t inverse_mask = (control_byte & 0x80) ? 0x7 : 0x0;
				pixels &= blink_mask;

				if(control_byte & 0x60) {
					if(data_type_ == Outputs::Display::InputDataType::Red1Green1Blue1 && rgb_pixel_target_) {
						const uint8_t colours[2] = {
							uint8_t(paper_ ^ inverse_mask),
							uint8_t(ink_ ^ inverse_mask)
						};
						rgb_pixel_target_[0] = colours[(pixels >> 5)&1];
						rgb_pixel_target_[1] = colours[(pixels >> 4)&1];
						rgb_pixel_target_[2] = colours[(pixels >> 3)&1];
						rgb_pixel_target_[3] = colours[(pixels >> 2)&1];
						rgb_pixel_target_[4] = colours[(pixels >> 1)&1];
						rgb_pixel_target_[5] = colours[(pixels >> 0)&1];
					} else if(composite_pixel_target_) {
						const uint32_t colours[2] = {
							colour_forms_[paper_ ^ inverse_mask],
							colour_forms_[ink_ ^ inverse_mask]
						};
						composite_pixel_target_[0] = colours[(pixels >> 5)&1];
						composite_pixel_target_[1] = colours[(pixels >> 4)&1];
						composite_pixel_target_[2] = colours[(pixels >> 3)&1];
						composite_pixel_target_[3] = colours[(pixels >> 2)&1];
						composite_pixel_target_[4] = colours[(pixels >> 1)&1];
						composite_pixel_target_[5] = colours[(pixels >> 0)&1];
					}
				} else {
					switch(control_byte & 0x1f) {
						case 0x00:		ink_ = 0x0;	break;
						case 0x01:		ink_ = 0x4;	break;
						case 0x02:		ink_ = 0x2;	break;
						case 0x03:		ink_ = 0x6;	break;
						case 0x04:		ink_ = 0x1;	break;
						case 0x05:		ink_ = 0x5;	break;
						case 0x06:		ink_ = 0x3;	break;
						case 0x07:		ink_ = 0x7;	break;

						case 0x08:	case 0x09:	case 0x0a: case 0x0b:
						case 0x0c:	case 0x0d:	case 0x0e: case 0x0f:
							use_alternative_character_set_ = (control_byte&1);
							use_double_height_characters_ = (control_byte&2);
							blink_text_ = (control_byte&4);
							set_character_set_base_address();
						break;

						case 0x10:		paper_ = 0x0;	break;
						case 0x11:		paper_ = 0x4;	break;
						case 0x12:		paper_ = 0x2;	break;
						case 0x13:		paper_ = 0x6;	break;
						case 0x14:		paper_ = 0x1;	break;
						case 0x15:		paper_ = 0x5;	break;
						case 0x16:		paper_ = 0x3;	break;
						case 0x17:		paper_ = 0x7;	break;

						case 0x18: case 0x19: case 0x1a: case 0x1b:
						case 0x1c: case 0x1d: case 0x1e: case 0x1f:
							is_graphics_mode_ = (control_byte & 4);
							next_frame_is_sixty_hertz_ = !(control_byte & 2);
						break;

						default: break;
					}

					if(data_type_ == Outputs::Display::InputDataType::Red1Green1Blue1 && rgb_pixel_target_) {
						rgb_pixel_target_[0] = rgb_pixel_target_[1] =
						rgb_pixel_target_[2] = rgb_pixel_target_[3] =
						rgb_pixel_target_[4] = rgb_pixel_target_[5] = paper_ ^ inverse_mask;
					} else if(composite_pixel_target_) {
						composite_pixel_target_[0] = composite_pixel_target_[1] =
						composite_pixel_target_[2] = composite_pixel_target_[3] =
						composite_pixel_target_[4] = composite_pixel_target_[5] = colour_forms_[paper_ ^ inverse_mask];
					}
				}
				if(rgb_pixel_target_) rgb_pixel_target_ += 6;
				if(composite_pixel_target_) composite_pixel_target_ += 6;
				h_counter++;
			}

			if(h_counter == 40) {
				crt_.output_data(40 * 6);
				rgb_pixel_target_ = nullptr;
				composite_pixel_target_ = nullptr;
			}
		} else {
			// this is a blank line (or the equivalent part of a pixel line)
			if(h_counter < 48) {
				cycles_run_for = 48 - h_counter;
				clamp(
					int period = (counter_ < 224*64) ? 8 : 48;
					crt_.output_blank(period * 6);
				);
			} else if(h_counter < 54) {
				cycles_run_for = 54 - h_counter;
				clamp(crt_.output_sync(6 * 6));
			} else if(h_counter < 56) {
				cycles_run_for = 56 - h_counter;
				clamp(crt_.output_default_colour_burst(2 * 6));
			} else {
				cycles_run_for = 64 - h_counter;
				clamp(crt_.output_blank(8 * 6));
			}
		}

		counter_ = (counter_ + cycles_run_for)%counter_period_;
		number_of_cycles -= cycles_run_for;
	}
}

void VideoOutput::set_character_set_base_address() {
	if(is_graphics_mode_) character_set_base_address_ = use_alternative_character_set_ ? 0x9c00 : 0x9800;
	else character_set_base_address_ = use_alternative_character_set_ ? 0xb800 : 0xb400;
}