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174 lines
5.3 KiB
C++
174 lines
5.3 KiB
C++
//
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// Video.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/04/2018.
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// Copyright © 2018 Thomas Harte. All rights reserved.
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//
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#ifndef Video_hpp
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#define Video_hpp
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#include "../../Outputs/CRT/CRT.hpp"
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include <vector>
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namespace AppleII {
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namespace Video {
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class BusHandler {
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public:
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uint8_t perform_read(uint16_t address) {
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return 0xff;
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}
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};
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template <class BusHandler> class Video {
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public:
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/// Constructs an instance of the video feed; a CRT is also created.
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Video(BusHandler &bus_handler) :
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bus_handler_(bus_handler),
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crt_(new Outputs::CRT::CRT(455, 1, Outputs::CRT::DisplayType::NTSC60, 1)) {
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// Set a composite sampling function that assumes 1bpp input, and uses just 7 bits per byte.
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crt_->set_composite_sampling_function(
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"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
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"{"
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"uint texValue = texture(sampler, coordinate).r;"
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"texValue <<= int(icoordinate.x * 8) & 7;"
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"return float(texValue & 128u);"
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// "uint texValue = texture(sampler, coordinate).r;"
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// "texValue <<= uint(icoordinate.x * 7.0) % 7u;"
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// "return float(texValue & 128u);"
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"}");
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// Show only the centre 75% of the TV frame.
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crt_->set_video_signal(Outputs::CRT::VideoSignal::Composite);
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crt_->set_visible_area(Outputs::CRT::Rect(0.115f, 0.117f, 0.77f, 0.77f));
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}
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/// @returns The CRT this video feed is feeding.
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Outputs::CRT::CRT *get_crt() {
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return crt_.get();
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}
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/*!
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Advances time by @c cycles; expects to be fed by the CPU clock.
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Implicitly adds an extra half a colour clock at the end of every
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line.
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*/
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void run_for(const Cycles cycles) {
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/*
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Addressing scheme used throughout is that column 0 is the first column with pixels in it;
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row 0 is the first row with pixels in it.
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A frame is oriented around 65 cycles across, 262 lines down.
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*/
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const int first_sync_line = 220; // A complete guess. Information needed.
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const int first_sync_column = 49; // Also a guess.
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int int_cycles = cycles.as_int();
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while(int_cycles) {
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const int cycles_this_line = std::min(65 - column_, int_cycles);
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if(row_ >= first_sync_line && row_ < first_sync_line + 3) {
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crt_->output_sync(static_cast<unsigned int>(cycles_this_line) * 7);
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} else {
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const int ending_column = column_ + cycles_this_line;
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// The first 40 columns are submitted to the CRT only upon completion;
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// they'll be either graphics or blank, depending on which side we are
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// of line 192.
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if(column_ < 40) {
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if(row_ < 192) {
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if(!column_) {
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pixel_pointer_ = crt_->allocate_write_area(40);
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}
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const int pixel_end = std::min(40, ending_column);
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const int character_row = row_ >> 3;
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const int pixel_row = row_ & 7;
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const uint16_t line_address = static_cast<uint16_t>(0x400 + (character_row >> 3) * 40 + ((character_row&7) << 7));
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for(int c = column_; c < pixel_end; ++c) {
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// TODO: proper address calculation.
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const uint16_t address = static_cast<uint16_t>(line_address + c);
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const uint8_t character = bus_handler_.perform_read(address);
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pixel_pointer_[c] = character_rom_[(static_cast<int>(character) << 3) + pixel_row];
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}
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if(ending_column >= 40) {
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crt_->output_data(280, 7);
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}
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} else {
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if(ending_column >= 40) {
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crt_->output_blank(280);
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}
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}
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}
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/*
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The left border, sync, right border pattern doesn't depend on whether
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there were pixels this row and is output as soon as it is known.
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*/
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const int first_blank_start = std::max(40, column_);
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const int first_blank_end = std::min(first_sync_column, ending_column);
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if(first_blank_end > first_blank_start) {
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crt_->output_blank(static_cast<unsigned int>(first_blank_end - first_blank_start) * 7);
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}
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// TODO: colour burst.
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const int sync_start = std::max(first_sync_column, column_);
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const int sync_end = std::min(first_sync_column + 4, ending_column);
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if(sync_end > sync_start) {
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crt_->output_sync(static_cast<unsigned int>(sync_end - sync_start) * 7);
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}
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const int second_blank_start = std::max(first_sync_column + 4, column_);
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if(ending_column > second_blank_start) {
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crt_->output_blank(static_cast<unsigned int>(ending_column - second_blank_start) * 7);
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}
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}
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int_cycles -= cycles_this_line;
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column_ = (column_ + cycles_this_line) % 65;
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if(!column_) {
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row_ = (row_ + 1) % 262;
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// Add an extra half a colour cycle of blank; this isn't counted in the run_for
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// count explicitly but is promised.
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crt_->output_blank(1);
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}
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}
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}
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// Inputs for the various soft switches.
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void set_graphics_mode() {}
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void set_text_mode() {}
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void set_mixed_mode(bool) {}
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void set_video_page(int) {}
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void set_low_resolution() {}
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void set_high_resolution() {}
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void set_character_rom(const std::vector<uint8_t> &character_rom) {
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character_rom_ = character_rom;
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}
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private:
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BusHandler &bus_handler_;
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std::unique_ptr<Outputs::CRT::CRT> crt_;
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int video_page_ = 0;
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int row_ = 0, column_ = 0;
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uint8_t *pixel_pointer_ = nullptr;
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std::vector<uint8_t> character_rom_;
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};
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}
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}
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#endif /* Video_hpp */
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