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479 lines
18 KiB
C++
479 lines
18 KiB
C++
//
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// Video.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 10/12/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "Video.hpp"
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#include <cstring>
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using namespace Electron;
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#define graphics_line(v) ((((v) >> 7) - first_graphics_line + field_divider_line) % field_divider_line)
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#define graphics_column(v) ((((v) & 127) - first_graphics_cycle + 128) & 127)
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namespace {
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static const int cycles_per_line = 128;
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static const int lines_per_frame = 625;
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static const int cycles_per_frame = lines_per_frame * cycles_per_line;
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static const int crt_cycles_multiplier = 8;
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static const int crt_cycles_per_line = crt_cycles_multiplier * cycles_per_line;
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static const int field_divider_line = 312; // i.e. the line, simultaneous with which, the first field's sync ends. So if
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// the first line with pixels in field 1 is the 20th in the frame, the first line
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// with pixels in field 2 will be 20+field_divider_line
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static const int first_graphics_line = 31;
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static const int first_graphics_cycle = 33;
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static const int display_end_interrupt_line = 256;
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static const int real_time_clock_interrupt_1 = 16704;
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static const int real_time_clock_interrupt_2 = 56704;
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static const int display_end_interrupt_1 = (first_graphics_line + display_end_interrupt_line)*cycles_per_line;
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static const int display_end_interrupt_2 = (first_graphics_line + field_divider_line + display_end_interrupt_line)*cycles_per_line;
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struct FourBPPBookender: public Outputs::CRT::TextureBuilder::Bookender {
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void add_bookends(uint8_t *const left_value, uint8_t *const right_value, uint8_t *left_bookend, uint8_t *right_bookend) {
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*left_bookend = static_cast<uint8_t>(((*left_value) & 0x0f) | (((*left_value) & 0x0f) << 4));
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*right_bookend = static_cast<uint8_t>(((*right_value) & 0xf0) | (((*right_value) & 0xf0) >> 4));
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}
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};
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}
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// MARK: - Lifecycle
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VideoOutput::VideoOutput(uint8_t *memory) : ram_(memory) {
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memset(palette_, 0xf, sizeof(palette_));
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setup_screen_map();
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setup_base_address();
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crt_.reset(new Outputs::CRT::CRT(crt_cycles_per_line, 8, Outputs::CRT::DisplayType::PAL50, 1));
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crt_->set_rgb_sampling_function(
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"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
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"{"
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"uint texValue = texture(sampler, coordinate).r;"
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"texValue >>= 4 - (int(icoordinate.x * 8) & 4);"
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"return vec3( uvec3(texValue) & uvec3(4u, 2u, 1u));"
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"}");
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std::unique_ptr<Outputs::CRT::TextureBuilder::Bookender> bookender(new FourBPPBookender);
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crt_->set_bookender(std::move(bookender));
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// TODO: as implied below, I've introduced a clock's latency into the graphics pipeline somehow. Investigate.
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crt_->set_visible_area(crt_->get_rect_for_area(first_graphics_line - 3, 256, (first_graphics_cycle+1) * crt_cycles_multiplier, 80 * crt_cycles_multiplier, 4.0f / 3.0f));
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}
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// MARK: - CRT getter
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Outputs::CRT::CRT *VideoOutput::get_crt() {
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return crt_.get();
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}
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// MARK: - Display update methods
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void VideoOutput::start_pixel_line() {
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current_pixel_line_ = (current_pixel_line_+1)&255;
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if(!current_pixel_line_) {
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start_line_address_ = start_screen_address_;
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current_character_row_ = 0;
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is_blank_line_ = false;
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} else {
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bool mode_has_blank_lines = (screen_mode_ == 6) || (screen_mode_ == 3);
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is_blank_line_ = (mode_has_blank_lines && ((current_character_row_ > 7 && current_character_row_ < 10) || (current_pixel_line_ > 249)));
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if(!is_blank_line_) {
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start_line_address_++;
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if(current_character_row_ > 7) {
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start_line_address_ += ((screen_mode_ < 4) ? 80 : 40) * 8 - 8;
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current_character_row_ = 0;
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}
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}
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}
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current_screen_address_ = start_line_address_;
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current_pixel_column_ = 0;
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initial_output_target_ = current_output_target_ = nullptr;
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}
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void VideoOutput::end_pixel_line() {
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if(current_output_target_) crt_->output_data(static_cast<unsigned int>((current_output_target_ - initial_output_target_) * current_output_divider_), current_output_divider_);
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current_character_row_++;
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}
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void VideoOutput::output_pixels(unsigned int number_of_cycles) {
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if(!number_of_cycles) return;
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if(is_blank_line_) {
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crt_->output_blank(number_of_cycles * crt_cycles_multiplier);
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} else {
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unsigned int divider = 1;
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switch(screen_mode_) {
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case 0: case 3: divider = 2; break;
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case 1: case 4: case 6: divider = 4; break;
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case 2: case 5: divider = 8; break;
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}
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if(!initial_output_target_ || divider != current_output_divider_) {
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if(current_output_target_) crt_->output_data(static_cast<unsigned int>((current_output_target_ - initial_output_target_) * current_output_divider_), current_output_divider_);
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current_output_divider_ = divider;
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initial_output_target_ = current_output_target_ = crt_->allocate_write_area(640 / current_output_divider_, 4);
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}
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#define get_pixel() \
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if(current_screen_address_&32768) {\
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current_screen_address_ = (screen_mode_base_address_ + current_screen_address_)&32767;\
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}\
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last_pixel_byte_ = ram_[current_screen_address_];\
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current_screen_address_ = current_screen_address_+8
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switch(screen_mode_) {
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case 0: case 3:
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if(initial_output_target_) {
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while(number_of_cycles--) {
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get_pixel();
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*reinterpret_cast<uint32_t *>(current_output_target_) = palette_tables_.eighty1bpp[last_pixel_byte_];
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current_output_target_ += 4;
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current_pixel_column_++;
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}
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} else current_output_target_ += 4*number_of_cycles;
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break;
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case 1:
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if(initial_output_target_) {
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while(number_of_cycles--) {
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get_pixel();
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*reinterpret_cast<uint16_t *>(current_output_target_) = palette_tables_.eighty2bpp[last_pixel_byte_];
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current_output_target_ += 2;
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current_pixel_column_++;
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}
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} else current_output_target_ += 2*number_of_cycles;
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break;
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case 2:
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if(initial_output_target_) {
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while(number_of_cycles--) {
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get_pixel();
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*current_output_target_ = palette_tables_.eighty4bpp[last_pixel_byte_];
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current_output_target_ += 1;
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current_pixel_column_++;
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}
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} else current_output_target_ += number_of_cycles;
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break;
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case 4: case 6:
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if(initial_output_target_) {
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if(current_pixel_column_&1) {
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last_pixel_byte_ <<= 4;
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*reinterpret_cast<uint16_t *>(current_output_target_) = palette_tables_.forty1bpp[last_pixel_byte_];
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current_output_target_ += 2;
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number_of_cycles--;
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current_pixel_column_++;
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}
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while(number_of_cycles > 1) {
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get_pixel();
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*reinterpret_cast<uint16_t *>(current_output_target_) = palette_tables_.forty1bpp[last_pixel_byte_];
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current_output_target_ += 2;
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last_pixel_byte_ <<= 4;
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*reinterpret_cast<uint16_t *>(current_output_target_) = palette_tables_.forty1bpp[last_pixel_byte_];
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current_output_target_ += 2;
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number_of_cycles -= 2;
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current_pixel_column_+=2;
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}
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if(number_of_cycles) {
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get_pixel();
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*reinterpret_cast<uint16_t *>(current_output_target_) = palette_tables_.forty1bpp[last_pixel_byte_];
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current_output_target_ += 2;
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current_pixel_column_++;
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}
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} else current_output_target_ += 2 * number_of_cycles;
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break;
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case 5:
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if(initial_output_target_) {
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if(current_pixel_column_&1) {
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last_pixel_byte_ <<= 2;
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*current_output_target_ = palette_tables_.forty2bpp[last_pixel_byte_];
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current_output_target_ += 1;
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number_of_cycles--;
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current_pixel_column_++;
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}
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while(number_of_cycles > 1) {
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get_pixel();
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*current_output_target_ = palette_tables_.forty2bpp[last_pixel_byte_];
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current_output_target_ += 1;
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last_pixel_byte_ <<= 2;
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*current_output_target_ = palette_tables_.forty2bpp[last_pixel_byte_];
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current_output_target_ += 1;
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number_of_cycles -= 2;
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current_pixel_column_+=2;
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}
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if(number_of_cycles) {
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get_pixel();
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*current_output_target_ = palette_tables_.forty2bpp[last_pixel_byte_];
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current_output_target_ += 1;
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current_pixel_column_++;
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}
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} else current_output_target_ += number_of_cycles;
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break;
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}
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#undef get_pixel
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}
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}
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void VideoOutput::run_for(const Cycles cycles) {
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int number_of_cycles = cycles.as_int();
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output_position_ = (output_position_ + number_of_cycles) % cycles_per_frame;
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while(number_of_cycles) {
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int draw_action_length = screen_map_[screen_map_pointer_].length;
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int time_left_in_action = std::min(number_of_cycles, draw_action_length - cycles_into_draw_action_);
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if(screen_map_[screen_map_pointer_].type == DrawAction::Pixels) output_pixels(static_cast<unsigned int>(time_left_in_action));
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number_of_cycles -= time_left_in_action;
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cycles_into_draw_action_ += time_left_in_action;
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if(cycles_into_draw_action_ == draw_action_length) {
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switch(screen_map_[screen_map_pointer_].type) {
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case DrawAction::Sync: crt_->output_sync(static_cast<unsigned int>(draw_action_length * crt_cycles_multiplier)); break;
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case DrawAction::ColourBurst: crt_->output_default_colour_burst(static_cast<unsigned int>(draw_action_length * crt_cycles_multiplier)); break;
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case DrawAction::Blank: crt_->output_blank(static_cast<unsigned int>(draw_action_length * crt_cycles_multiplier)); break;
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case DrawAction::Pixels: end_pixel_line(); break;
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}
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screen_map_pointer_ = (screen_map_pointer_ + 1) % screen_map_.size();
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cycles_into_draw_action_ = 0;
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if(screen_map_[screen_map_pointer_].type == DrawAction::Pixels) start_pixel_line();
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}
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}
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}
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// MARK: - Register hub
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void VideoOutput::set_register(int address, uint8_t value) {
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switch(address & 0xf) {
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case 0x02:
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start_screen_address_ = (start_screen_address_ & 0xfe00) | static_cast<uint16_t>((value & 0xe0) << 1);
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if(!start_screen_address_) start_screen_address_ |= 0x8000;
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break;
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case 0x03:
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start_screen_address_ = (start_screen_address_ & 0x01ff) | static_cast<uint16_t>((value & 0x3f) << 9);
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if(!start_screen_address_) start_screen_address_ |= 0x8000;
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break;
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case 0x07: {
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// update screen mode
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uint8_t new_screen_mode = (value >> 3)&7;
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if(new_screen_mode == 7) new_screen_mode = 4;
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if(new_screen_mode != screen_mode_) {
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screen_mode_ = new_screen_mode;
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setup_base_address();
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}
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}
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break;
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case 0x08: case 0x09: case 0x0a: case 0x0b:
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case 0x0c: case 0x0d: case 0x0e: case 0x0f: {
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static const int registers[4][4] = {
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{10, 8, 2, 0},
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{14, 12, 6, 4},
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{15, 13, 7, 5},
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{11, 9, 3, 1},
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};
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const int index = (address >> 1)&3;
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const uint8_t colour = ~value;
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if(address&1) {
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palette_[registers[index][0]] = (palette_[registers[index][0]]&3) | ((colour >> 1)&4);
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palette_[registers[index][1]] = (palette_[registers[index][1]]&3) | ((colour >> 0)&4);
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palette_[registers[index][2]] = (palette_[registers[index][2]]&3) | ((colour << 1)&4);
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palette_[registers[index][3]] = (palette_[registers[index][3]]&3) | ((colour << 2)&4);
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palette_[registers[index][2]] = (palette_[registers[index][2]]&5) | ((colour >> 4)&2);
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palette_[registers[index][3]] = (palette_[registers[index][3]]&5) | ((colour >> 3)&2);
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} else {
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palette_[registers[index][0]] = (palette_[registers[index][0]]&6) | ((colour >> 7)&1);
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palette_[registers[index][1]] = (palette_[registers[index][1]]&6) | ((colour >> 6)&1);
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palette_[registers[index][2]] = (palette_[registers[index][2]]&6) | ((colour >> 5)&1);
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palette_[registers[index][3]] = (palette_[registers[index][3]]&6) | ((colour >> 4)&1);
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palette_[registers[index][0]] = (palette_[registers[index][0]]&5) | ((colour >> 2)&2);
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palette_[registers[index][1]] = (palette_[registers[index][1]]&5) | ((colour >> 1)&2);
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}
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// regenerate all palette tables for now
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#define pack(a, b) static_cast<uint8_t>((a << 4) | (b))
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for(int byte = 0; byte < 256; byte++) {
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uint8_t *target = reinterpret_cast<uint8_t *>(&palette_tables_.forty1bpp[byte]);
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target[0] = pack(palette_[(byte&0x80) >> 4], palette_[(byte&0x40) >> 3]);
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target[1] = pack(palette_[(byte&0x20) >> 2], palette_[(byte&0x10) >> 1]);
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target = reinterpret_cast<uint8_t *>(&palette_tables_.eighty2bpp[byte]);
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target[0] = pack(palette_[((byte&0x80) >> 4) | ((byte&0x08) >> 2)], palette_[((byte&0x40) >> 3) | ((byte&0x04) >> 1)]);
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target[1] = pack(palette_[((byte&0x20) >> 2) | ((byte&0x02) >> 0)], palette_[((byte&0x10) >> 1) | ((byte&0x01) << 1)]);
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target = reinterpret_cast<uint8_t *>(&palette_tables_.eighty1bpp[byte]);
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target[0] = pack(palette_[(byte&0x80) >> 4], palette_[(byte&0x40) >> 3]);
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target[1] = pack(palette_[(byte&0x20) >> 2], palette_[(byte&0x10) >> 1]);
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target[2] = pack(palette_[(byte&0x08) >> 0], palette_[(byte&0x04) << 1]);
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target[3] = pack(palette_[(byte&0x02) << 2], palette_[(byte&0x01) << 3]);
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palette_tables_.forty2bpp[byte] = pack( palette_[((byte&0x80) >> 4) | ((byte&0x08) >> 2)], palette_[((byte&0x40) >> 3) | ((byte&0x04) >> 1)]);
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palette_tables_.eighty4bpp[byte] = pack( palette_[((byte&0x80) >> 4) | ((byte&0x20) >> 3) | ((byte&0x08) >> 2) | ((byte&0x02) >> 1)],
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palette_[((byte&0x40) >> 3) | ((byte&0x10) >> 2) | ((byte&0x04) >> 1) | ((byte&0x01) >> 0)]);
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}
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#undef pack
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}
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break;
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}
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}
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void VideoOutput::setup_base_address() {
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switch(screen_mode_) {
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case 0: case 1: case 2: screen_mode_base_address_ = 0x3000; break;
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case 3: screen_mode_base_address_ = 0x4000; break;
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case 4: case 5: screen_mode_base_address_ = 0x5800; break;
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case 6: screen_mode_base_address_ = 0x6000; break;
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}
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}
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// MARK: - Interrupts
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VideoOutput::Interrupt VideoOutput::get_next_interrupt() {
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VideoOutput::Interrupt interrupt;
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if(output_position_ < real_time_clock_interrupt_1) {
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interrupt.cycles = real_time_clock_interrupt_1 - output_position_;
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interrupt.interrupt = RealTimeClock;
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return interrupt;
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}
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if(output_position_ < display_end_interrupt_1) {
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interrupt.cycles = display_end_interrupt_1 - output_position_;
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interrupt.interrupt = DisplayEnd;
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return interrupt;
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}
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if(output_position_ < real_time_clock_interrupt_2) {
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interrupt.cycles = real_time_clock_interrupt_2 - output_position_;
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interrupt.interrupt = RealTimeClock;
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return interrupt;
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}
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if(output_position_ < display_end_interrupt_2) {
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interrupt.cycles = display_end_interrupt_2 - output_position_;
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interrupt.interrupt = DisplayEnd;
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return interrupt;
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}
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interrupt.cycles = real_time_clock_interrupt_1 + cycles_per_frame - output_position_;
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interrupt.interrupt = RealTimeClock;
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return interrupt;
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}
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// MARK: - RAM timing and access information
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unsigned int VideoOutput::get_cycles_until_next_ram_availability(int from_time) {
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unsigned int result = 0;
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int position = (output_position_ + from_time) % cycles_per_frame;
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// Apply the standard cost of aligning to the available 1Mhz of RAM bandwidth.
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result += 1 + (position&1);
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// In Modes 0–3 there is also a complete block on any access while pixels are being fetched.
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if(screen_mode_ < 4) {
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const int current_column = graphics_column(position + (position&1));
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int current_line = graphics_line(position);
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if(current_column < 80 && current_line < 256) {
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// Mode 3 is a further special case: in 'every ten line block', the final two aren't painted,
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// so the CPU is allowed access. But the offset of the ten-line blocks depends on when the
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// user switched into Mode 3, so that needs to be calculated relative to current output.
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if(screen_mode_ == 3) {
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// Get the line the display was on.
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int output_position_line = graphics_line(output_position_);
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int implied_row;
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if(current_line >= output_position_line) {
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// Get the number of lines since then if still in the same frame.
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int lines_since_output_position = current_line - output_position_line;
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// Therefore get the character row at the proposed time, modulo 10.
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implied_row = (current_character_row_ + lines_since_output_position) % 10;
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} else {
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// If the frame has rolled over, the implied row is just related to the current line.
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implied_row = current_line % 10;
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}
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// Mode 3 ends after 250 lines, not the usual 256.
|
||
if(implied_row < 8 && current_line < 250) result += static_cast<unsigned int>(80 - current_column);
|
||
}
|
||
else result += static_cast<unsigned int>(80 - current_column);
|
||
}
|
||
}
|
||
return result;
|
||
}
|
||
|
||
VideoOutput::Range VideoOutput::get_memory_access_range() {
|
||
// This can't be more specific than this without applying a lot more thought because of mixed modes:
|
||
// suppose a program runs half the screen in an 80-column mode then switches to 40 columns. Then the
|
||
// real end address will be at 128*80 + 128*40 after the original base, subject to wrapping that depends
|
||
// on where the overflow occurred. Assuming accesses may run from the lowest possible position through to
|
||
// the end of RAM is good enough for 95% of use cases however.
|
||
VideoOutput::Range range;
|
||
range.low_address = std::min(start_screen_address_, screen_mode_base_address_);
|
||
range.high_address = 0x8000;
|
||
return range;
|
||
}
|
||
|
||
// MARK: - The screen map
|
||
|
||
void VideoOutput::setup_screen_map() {
|
||
/*
|
||
|
||
Odd field: Even field:
|
||
|
||
|--S--| -S-|
|
||
|--S--| |--S--|
|
||
|-S-B-| = 3 |--S--| = 2.5
|
||
|--B--| |--B--|
|
||
|--P--| |--P--|
|
||
|--B--| = 312 |--B--| = 312.5
|
||
|-B-
|
||
|
||
*/
|
||
for(int c = 0; c < 2; c++) {
|
||
if(c&1) {
|
||
screen_map_.emplace_back(DrawAction::Sync, (cycles_per_line * 5) >> 1);
|
||
screen_map_.emplace_back(DrawAction::Blank, cycles_per_line >> 1);
|
||
} else {
|
||
screen_map_.emplace_back(DrawAction::Blank, cycles_per_line >> 1);
|
||
screen_map_.emplace_back(DrawAction::Sync, (cycles_per_line * 5) >> 1);
|
||
}
|
||
for(int l = 0; l < first_graphics_line - 3; l++) emplace_blank_line();
|
||
for(int l = 0; l < 256; l++) emplace_pixel_line();
|
||
for(int l = 256 + first_graphics_line; l < 312; l++) emplace_blank_line();
|
||
if(c&1) emplace_blank_line();
|
||
}
|
||
}
|
||
|
||
void VideoOutput::emplace_blank_line() {
|
||
screen_map_.emplace_back(DrawAction::Sync, 9);
|
||
screen_map_.emplace_back(DrawAction::ColourBurst, 24 - 9);
|
||
screen_map_.emplace_back(DrawAction::Blank, 128 - 24);
|
||
}
|
||
|
||
void VideoOutput::emplace_pixel_line() {
|
||
// output format is:
|
||
// 9 cycles: sync
|
||
// ... to 24 cycles: colour burst
|
||
// ... to first_graphics_cycle: blank
|
||
// ... for 80 cycles: pixels
|
||
// ... until end of line: blank
|
||
screen_map_.emplace_back(DrawAction::Sync, 9);
|
||
screen_map_.emplace_back(DrawAction::ColourBurst, 24 - 9);
|
||
screen_map_.emplace_back(DrawAction::Blank, first_graphics_cycle - 24);
|
||
screen_map_.emplace_back(DrawAction::Pixels, 80);
|
||
screen_map_.emplace_back(DrawAction::Blank, 48 - first_graphics_cycle);
|
||
}
|