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138 lines
4.0 KiB
C++
138 lines
4.0 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 14/04/2018.
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// Copyright 2018 Thomas Harte. All rights reserved.
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//
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#include "Video.hpp"
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using namespace AppleII::Video;
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namespace {
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struct ScaledByteFiller {
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ScaledByteFiller() {
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VideoBase::setup_tables();
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}
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} throwaway;
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}
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VideoBase::VideoBase() :
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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) % 7;"
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"return float(texValue & 1u);"
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"}");
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crt_->set_integer_coordinate_multiplier(7.0f);
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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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crt_->set_immediate_default_phase(0.0f);
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}
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Outputs::CRT::CRT *VideoBase::get_crt() {
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return crt_.get();
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}
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uint16_t VideoBase::scaled_byte[256];
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uint16_t VideoBase::low_resolution_patterns[2][16];
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void VideoBase::setup_tables() {
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// Rules of Apple II high resolution video:
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//
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// Bit 0 appears on screen first. Then bit 1. Etc to bit 6.
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//
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// If bit 7 is set, the whole serialisation is delayed for half a pixel, holding
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// whichever level was previously being output.
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for(int c = 0; c < 128; ++c) {
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const uint16_t value =
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((c & 0x01) ? 0x0003 : 0x0000) |
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((c & 0x02) ? 0x000c : 0x0000) |
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((c & 0x04) ? 0x0030 : 0x0000) |
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((c & 0x08) ? 0x0140 : 0x0000) |
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((c & 0x10) ? 0x0600 : 0x0000) |
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((c & 0x20) ? 0x1800 : 0x0000) |
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((c & 0x40) ? 0x6000 : 0x0000);
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uint8_t *const table_entry = reinterpret_cast<uint8_t *>(&scaled_byte[c]);
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table_entry[0] = static_cast<uint8_t>(value & 0xff);
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table_entry[1] = static_cast<uint8_t>(value >> 8);
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}
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for(int c = 128; c < 256; ++c) {
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uint8_t *const source_table_entry = reinterpret_cast<uint8_t *>(&scaled_byte[c & 0x7f]);
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uint8_t *const destination_table_entry = reinterpret_cast<uint8_t *>(&scaled_byte[c]);
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destination_table_entry[0] = static_cast<uint8_t>(source_table_entry[0] << 1);
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destination_table_entry[1] = static_cast<uint8_t>((source_table_entry[1] << 1) | (source_table_entry[0] >> 6));
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}
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for(int c = 0; c < 16; ++c) {
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// Produce the whole 28-bit pattern that would cover two columns.
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int pattern = 0;
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for(int l = 0; l < 7; ++l) {
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pattern <<= 4;
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pattern |= c;
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}
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// Pack that 28-bit pattern into the appropriate look-up tables.
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uint8_t *const left_entry = reinterpret_cast<uint8_t *>(&low_resolution_patterns[0][c]);
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uint8_t *const right_entry = reinterpret_cast<uint8_t *>(&low_resolution_patterns[1][c]);
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left_entry[0] = static_cast<uint8_t>(pattern);
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left_entry[1] = static_cast<uint8_t>(pattern >> 7);
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right_entry[0] = static_cast<uint8_t>(pattern >> 14);
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right_entry[1] = static_cast<uint8_t>(pattern >> 21);
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}
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}
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void VideoBase::set_graphics_mode() {
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use_graphics_mode_ = true;
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}
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void VideoBase::set_text_mode() {
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use_graphics_mode_ = false;
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}
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void VideoBase::set_mixed_mode(bool mixed_mode) {
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mixed_mode_ = mixed_mode;
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}
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void VideoBase::set_video_page(int page) {
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video_page_ = page;
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}
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void VideoBase::set_low_resolution() {
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graphics_mode_ = GraphicsMode::LowRes;
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}
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void VideoBase::set_high_resolution() {
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graphics_mode_ = GraphicsMode::HighRes;
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}
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void VideoBase::set_character_rom(const std::vector<uint8_t> &character_rom) {
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character_rom_ = character_rom;
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// Bytes in the character ROM are stored in reverse bit order. Reverse them
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// ahead of time so as to be able to use the same scaling table as for
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// high-resolution graphics.
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for(auto &byte : character_rom_) {
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byte =
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((byte & 0x40) ? 0x01 : 0x00) |
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((byte & 0x20) ? 0x02 : 0x00) |
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((byte & 0x10) ? 0x04 : 0x00) |
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((byte & 0x08) ? 0x08 : 0x00) |
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((byte & 0x04) ? 0x10 : 0x00) |
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((byte & 0x02) ? 0x20 : 0x00) |
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((byte & 0x01) ? 0x40 : 0x00) |
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(byte & 0x80);
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}
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}
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