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Starts to make some attempt at classic II modes.
This commit is contained in:
Thomas Harte
parent
4a42de4f18
commit
4b024c5787
@ -56,6 +56,22 @@ VideoBase::VideoBase() :
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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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crt_.set_visible_area(Outputs::Display::Rect(0.097f, 0.1f, 0.85f, 0.85f));
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// Establish the shift lookup table for NTSC -> RGB output.
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for(int c = 0; c < 256; c++) {
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const auto top_nibble = c >> 4;
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// Otherwise, check for descending disagreements.
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ntsc_shift_lookup_[c] = 4;
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int mask = 0x10;
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while(mask) {
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if((top_nibble & mask) != (c & mask)) break;
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mask >>= 1;
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--ntsc_shift_lookup_[c];
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}
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ntsc_shift_lookup_[c] &= 3;
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}
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}
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void VideoBase::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
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@ -197,6 +213,7 @@ void VideoBase::output_row(int row, int start, int end) {
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if(start == start_of_pixels) {
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// 640 is the absolute most number of pixels that might be generated
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// printf("Begin\n");
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next_pixel_ = pixels_ = reinterpret_cast<uint16_t *>(crt_.begin_data(640, 2));
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// YUCKY HACK. I do not know when the IIgs fetches its super high-res palette
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@ -232,6 +249,12 @@ void VideoBase::output_row(int row, int start, int end) {
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case Apple::II::GraphicsMode::DoubleText:
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next_pixel_ = output_double_text(next_pixel_, window_start, window_end, row);
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break;
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case Apple::II::GraphicsMode::LowRes:
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next_pixel_ = output_low_resolution(next_pixel_, window_start, window_end, row);
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break;
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case Apple::II::GraphicsMode::HighRes:
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next_pixel_ = output_high_resolution(next_pixel_, window_start, window_end, row);
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break;
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default:
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assert(false);
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@ -243,6 +266,7 @@ void VideoBase::output_row(int row, int start, int end) {
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}
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if(end_of_period == start_of_right_border) {
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// printf("Output\n");
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crt_.output_data((start_of_right_border - start_of_pixels) * CyclesPerTick, next_pixel_ ? size_t(next_pixel_ - pixels_) : 1);
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next_pixel_ = pixels_ = nullptr;
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}
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@ -405,3 +429,115 @@ uint16_t *VideoBase::output_super_high_res(uint16_t *target, int start, int end,
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return target;
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}
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uint16_t *VideoBase::output_low_resolution(uint16_t *target, int start, int end, int row) {
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const int row_shift = row&4;
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const uint16_t row_address = get_row_address(row);
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for(int c = start; c < end; c++) {
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ntsc_shift_ <<= 14;
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const uint8_t source = ram_[row_address + c] >> row_shift;
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// Convulve input as a function of odd/even row.
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if((start + c)&1) {
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ntsc_shift_ |= ((source & 4) >> 2) * 0x2222;
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ntsc_shift_ |= ((source & 8) >> 3) * 0x1111;
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ntsc_shift_ |= ((source & 1) >> 0) * 0x0888;
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ntsc_shift_ |= ((source & 2) >> 1) * 0x0444;
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} else {
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ntsc_shift_ |= ((source & 1) >> 0) * 0x2222;
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ntsc_shift_ |= ((source & 2) >> 1) * 0x1111;
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ntsc_shift_ |= ((source & 4) >> 2) * 0x0888;
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ntsc_shift_ |= ((source & 8) >> 3) * 0x0444;
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}
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// TODO: initial state?
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target = output_shift(target, (c * 14) & 3);
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}
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return target;
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}
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uint16_t *VideoBase::output_high_resolution(uint16_t *target, int start, int end, int row) {
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const uint16_t row_address = get_row_address(row);
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for(int c = start; c < end; c++) {
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ntsc_shift_ <<= 14;
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uint8_t source = ram_[row_address + c];
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// HACK: bit reverse, for now.
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// Because I'd forgotten which order the Apple II serialises bits in, and have predicated too much upon it.
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source = ((source >> 6) & 0x01) | ((source >> 4) & 0x02) | ((source >> 2) & 0x04) | ((source >> 0) & 0x08) | ((source << 2) & 0x10) | ((source << 4) & 0x20) | ((source << 6) & 0x40);
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// TODO: can do this in two multiplies, I think.
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const uint16_t doubled_source =
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((source&0x01) * (0x0003 >> 0)) +
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((source&0x02) * (0x000c >> 1)) +
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((source&0x04) * (0x0030 >> 2)) +
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((source&0x08) * (0x00c0 >> 3)) +
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((source&0x10) * (0x0300 >> 4)) +
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((source&0x20) * (0x0c00 >> 5)) +
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((source&0x40) * (0x3000 >> 6));
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// Just append new bits, doubled up (and possibly delayed).
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// TODO: I can kill the conditional here.
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if(source & high_resolution_mask_ & 0x80) {
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ntsc_shift_ |= ((ntsc_shift_ >> 1) & 0x2000) | (doubled_source >> 1);
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} else {
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ntsc_shift_ |= doubled_source;
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}
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// TODO: initial state?
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target = output_shift(target, (c * 14) & 3);
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}
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return target;
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}
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uint16_t *VideoBase::output_shift(uint16_t *target, int phase) const {
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constexpr uint8_t rolls[4][16] = {
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{
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0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf
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},
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{
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0x0, 0x8, 0x1, 0x9, 0x2, 0xa, 0x3, 0xb,
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0x4, 0xc, 0x5, 0xd, 0x6, 0xe, 0x7, 0xf
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},
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{
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0x0, 0x4, 0x8, 0xc, 0x1, 0x5, 0x9, 0xd,
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0x2, 0x6, 0xa, 0xe, 0x3, 0x7, 0xb, 0xf
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},
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{
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0x0, 0x2, 0x4, 0x6, 0x8, 0xa, 0xc, 0xe,
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0x1, 0x3, 0x5, 0x7, 0x9, 0xb, 0xd, 0xf
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},
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};
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#define OutputPixel(offset) {\
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const auto phase_offset = ntsc_shift_lookup_[(ntsc_shift_ >> offset) & 0xff]; \
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const auto raw_bits = (ntsc_shift_ >> (offset + phase_offset)) & 0x0f; \
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target[13 - offset] = appleii_palette[rolls[(phase + 13 - offset - phase_offset)&3][raw_bits]]; \
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}
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//#define OutputPixel(offset) {\
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// target[13 - offset] = appleii_palette[(ntsc_shift_ >> offset) & 0xf]; \
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//}
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OutputPixel(13);
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OutputPixel(12);
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OutputPixel(11);
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OutputPixel(10);
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OutputPixel(9);
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OutputPixel(8);
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OutputPixel(7);
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OutputPixel(6);
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OutputPixel(5);
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OutputPixel(4);
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OutputPixel(3);
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OutputPixel(2);
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OutputPixel(1);
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OutputPixel(0);
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#undef OutputPixel
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return target + 14;
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}
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@ -87,9 +87,32 @@ class VideoBase: public Apple::II::VideoSwitches<Cycles> {
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uint16_t *output_double_text(uint16_t *target, int start, int end, int row) const;
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uint16_t *output_char(uint16_t *target, uint8_t source, int row) const;
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uint16_t *output_low_resolution(uint16_t *target, int start, int end, int row);
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uint16_t *output_high_resolution(uint16_t *target, int start, int end, int row);
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// Super high-res per-line state.
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uint8_t line_control_;
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uint16_t palette_[16];
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// Lookup tables and state to assist in the IIgs' mapping from NTSC to RGB.
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//
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// My understanding of the real-life algorithm is: maintain a four-bit buffer.
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// Fill it in a circular fashion. Ordinarily, output the result of looking
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// up the RGB mapping of those four bits of Apple II output (which outputs four
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// bits per NTSC colour cycle), commuted as per current phase. But if the bit
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// being inserted differs from that currently in its position in the shift
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// register, hold the existing output for three shifts.
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//
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// From there I am using the following:
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// Maps from the most recent eight bits of Apple II output to how far back
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// into history the graphics system should look for output.
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uint8_t ntsc_shift_lookup_[256];
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int ntsc_shift_ = 0;
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/// Outputs the lowest 14 bits from @c ntsc_shift_, mapping to RGB.
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uint16_t *output_shift(uint16_t *target, int phase) const;
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};
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class Video: public VideoBase {
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