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257 lines
8.5 KiB
C++
257 lines
8.5 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 31/10/2020.
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// Copyright © 2020 Thomas Harte. All rights reserved.
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//
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#include "Video.hpp"
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using namespace Apple::IIgs::Video;
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namespace {
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constexpr int CyclesPerTick = 7; // One 'tick' being the non-stretched length of a cycle on the old Apple II 1Mhz clock.
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constexpr int CyclesPerLine = 456; // Each of the Mega II's cycles lasts 7 cycles, making 455/line except for the
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// final on on a line which lasts an additional 1 (i.e. is 1/7th longer).
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constexpr int Lines = 263;
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constexpr int FinalPixelLine = 192;
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constexpr auto FinalColumn = CyclesPerLine / CyclesPerTick;
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// Converts from Apple's RGB ordering to this emulator's.
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#define PaletteConvulve(x) ((x&0xf00) >> 8) | ((x&0x00f) << 8) | (x&0x0f0)
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// The 12-bit values used by the Apple IIgs to approximate Apple II colours,
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// as implied by tech note #63's use of them as border colours.
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// http://www.1000bit.it/support/manuali/apple/technotes/iigs/tn.iigs.063.html
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constexpr uint16_t appleii_palette[16] = {
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PaletteConvulve(0x0000), // Black.
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PaletteConvulve(0x0d03), // Deep Red.
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PaletteConvulve(0x0009), // Dark Blue.
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PaletteConvulve(0x0d2d), // Purple.
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PaletteConvulve(0x0072), // Dark Green.
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PaletteConvulve(0x0555), // Dark Gray.
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PaletteConvulve(0x022f), // Medium Blue.
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PaletteConvulve(0x06af), // Light Blue.
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PaletteConvulve(0x0850), // Brown.
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PaletteConvulve(0x0f60), // Orange.
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PaletteConvulve(0x0aaa), // Light Grey.
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PaletteConvulve(0x0f98), // Pink.
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PaletteConvulve(0x01d0), // Light Green.
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PaletteConvulve(0x0ff0), // Yellow.
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PaletteConvulve(0x04f9), // Aquamarine.
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PaletteConvulve(0x0fff), // White.
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};
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}
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VideoBase::VideoBase() :
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VideoSwitches<Cycles>(true, Cycles(2), [this] (Cycles cycles) { advance(cycles); }),
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crt_(CyclesPerLine - 1, 1, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Red4Green4Blue4) {
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crt_.set_display_type(Outputs::Display::DisplayType::RGB);
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}
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void VideoBase::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
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crt_.set_scan_target(scan_target);
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}
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Outputs::Display::ScanStatus VideoBase::get_scaled_scan_status() const {
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return crt_.get_scaled_scan_status();
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}
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void VideoBase::set_display_type(Outputs::Display::DisplayType display_type) {
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crt_.set_display_type(display_type);
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}
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Outputs::Display::DisplayType VideoBase::get_display_type() const {
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return crt_.get_display_type();
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}
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void VideoBase::set_internal_ram(const uint8_t *ram) {
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ram_ = ram;
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}
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void VideoBase::advance(Cycles cycles) {
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const int column_start = (cycles_into_frame_ % CyclesPerLine) / CyclesPerTick;
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const int row_start = cycles_into_frame_ / CyclesPerLine;
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cycles_into_frame_ = (cycles_into_frame_ + cycles.as<int>()) % (CyclesPerLine * Lines);
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const int column_end = (cycles_into_frame_ % CyclesPerLine) / CyclesPerTick;
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const int row_end = cycles_into_frame_ / CyclesPerLine;
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if(row_end == row_start) {
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if(column_end != column_start) {
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output_row(row_start, column_start, column_end);
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}
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} else {
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if(column_start != FinalColumn) {
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output_row(row_start, column_start, FinalColumn);
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}
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for(int row = row_start+1; row < row_end; row++) {
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output_row(row, 0, FinalColumn);
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}
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if(column_end) {
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output_row(row_end, 0, column_end);
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}
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}
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}
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void VideoBase::output_row(int row, int start, int end) {
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// Reasoned guesswork ahoy!
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//
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// The IIgs VGC can fetch four bytes per column — I'm unclear physically how, but that's definitely true
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// since the IIgs modes packs 160 bytes work of graphics into the Apple II's usual 40-cycle fetch area;
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// it's possible that if I understood the meaning of the linear video bit in the new video flag I'd know more.
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//
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// Super Hi-Res also fetches 16*2 = 32 bytes of palette and a control byte sometime before each row.
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// So it needs five windows for that.
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//
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// Guessing four cycles of sync, I've chosen to arrange one output row for this emulator as:
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//
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// 5 cycles of back porch;
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// 8 windows left border, the final five of which fetch palette and control if in IIgs mode;
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// 40 windows of pixel output;
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// 8 cycles of right border;
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// 4 cycles of sync (including the extra 1/7th window, as it has to go _somewhere_).
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//
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// Otherwise, the first 200 rows may be pixels and the 192 in the middle of those are the II set.
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constexpr int first_sync_line = 220; // A complete guess. Information needed.
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constexpr int blank_ticks = 5;
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constexpr int left_border_ticks = 8;
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constexpr int pixel_ticks = 40;
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constexpr int right_border_ticks = 8;
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constexpr int start_of_left_border = blank_ticks;
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constexpr int start_of_pixels = start_of_left_border + left_border_ticks;
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constexpr int start_of_right_border = start_of_pixels + pixel_ticks;
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constexpr int start_of_sync = start_of_right_border + right_border_ticks;
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constexpr int sync_period = CyclesPerLine - start_of_sync*CyclesPerTick;
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// Deal with vertical sync.
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if(row >= first_sync_line && row < first_sync_line + 3) {
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// Simplification: just output the whole line at line's end.
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if(end == FinalColumn) {
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crt_.output_sync(CyclesPerLine - sync_period);
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crt_.output_blank(sync_period);
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}
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return;
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}
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// Pixel or pure border => blank as usual.
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// Output blank only at the end of its window.
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if(start < blank_ticks && end >= blank_ticks) {
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crt_.output_blank(blank_ticks * CyclesPerTick);
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start = blank_ticks;
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if(start == end) return;
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}
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// Possibly output border, pixels, border, if this is a pixel line.
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if(row < 192 + ((new_video_&0x80) >> 4)) { // i.e. 192 lines for classic Apple II video, 200 for IIgs video.
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// Output left border as far as currently known.
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if(start >= start_of_left_border && start < start_of_pixels) {
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const int end_of_period = std::min(start_of_pixels, end);
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uint16_t *const pixel = reinterpret_cast<uint16_t *>(crt_.begin_data(2, 2));
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if(pixel) *pixel = border_colour_;
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crt_.output_data((end_of_period - start) * CyclesPerTick, 1);
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start = end_of_period;
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if(start == end) return;
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}
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// Output left border as far as currently known.
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if(start >= start_of_pixels && start < start_of_right_border) {
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const int end_of_period = std::min(start_of_right_border, end);
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// TODO: output real pixels.
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uint16_t *const pixel = reinterpret_cast<uint16_t *>(crt_.begin_data(2, 2));
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if(pixel) *pixel = appleii_palette[7];
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crt_.output_data((end_of_period - start) * CyclesPerTick, 1);
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start = end_of_period;
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if(start == end) return;
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}
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// Output left border as far as currently known.
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if(start >= start_of_right_border && start < start_of_sync) {
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const int end_of_period = std::min(start_of_sync, end);
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uint16_t *const pixel = reinterpret_cast<uint16_t *>(crt_.begin_data(2, 2));
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if(pixel) *pixel = border_colour_;
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crt_.output_data((end_of_period - start) * CyclesPerTick, 1);
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// There's no point updating start here; just fall
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// through to the end == FinalColumn test.
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}
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} else {
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// This line is all border, all the time.
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if(start >= start_of_left_border && start < start_of_sync) {
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const int end_of_period = std::min(start_of_sync, end);
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uint16_t *const pixel = reinterpret_cast<uint16_t *>(crt_.begin_data(2, 2));
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if(pixel) *pixel = border_colour_;
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crt_.output_data((end_of_period - start) * CyclesPerTick, 1);
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start = end_of_period;
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if(start == end) return;
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}
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}
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// Output sync if the moment has arrived.
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if(end == FinalColumn) {
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crt_.output_sync(sync_period);
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}
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}
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bool VideoBase::get_is_vertical_blank() {
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// Cf. http://www.1000bit.it/support/manuali/apple/technotes/iigs/tn.iigs.040.html ;
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// this bit covers the entire vertical border area, not just the NTSC-sense vertical blank.
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return cycles_into_frame_ >= FinalPixelLine * CyclesPerLine;
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}
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void VideoBase::set_new_video(uint8_t new_video) {
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new_video_ = new_video;
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}
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uint8_t VideoBase::get_new_video() {
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return new_video_;
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}
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void VideoBase::clear_interrupts(uint8_t mask) {
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set_interrupts(interrupts_ & ~(mask & 0x60));
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}
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void VideoBase::set_interrupt_register(uint8_t mask) {
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set_interrupts(interrupts_ | (mask & 0x6));
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}
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uint8_t VideoBase::get_interrupt_register() {
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return interrupts_;
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}
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void VideoBase::notify_clock_tick() {
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set_interrupts(interrupts_ | 0x40);
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}
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void VideoBase::set_interrupts(uint8_t new_value) {
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interrupts_ = new_value & 0x7f;
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if((interrupts_ >> 4) & interrupts_ & 0x6)
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interrupts_ |= 0x80;
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}
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void VideoBase::set_border_colour(uint8_t colour) {
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border_colour_ = appleii_palette[colour & 0xf];
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}
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void VideoBase::set_text_colour(uint8_t colour) {
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text_colour_ = appleii_palette[colour >> 4];
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background_colour_ = appleii_palette[colour & 0xf];
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}
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