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Corrects low-resolution mode.

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This commit is contained in:
Thomas Harte 2020-11-22 20:52:42 -05:00
parent b0936b6ef4
commit cd7d080b7a
1 changed files with 17 additions and 16 deletions
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33
Machines/Apple/AppleIIgs/Video.cpp
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@ -441,27 +441,28 @@ uint16_t *VideoBase::output_low_resolution(uint16_t *target, int start, int end,
const int row_shift = row&4;
const uint16_t row_address = get_row_address(row);
for(int c = start; c < end; c++) {
ntsc_shift_ >>= 14;
const uint8_t source = ram_[row_address + c] >> row_shift;
// TODO: below is all wrong, now that I've corrected ntsc_shift_ direction.
const uint8_t source = (ram_[row_address + c] >> row_shift) & 0xf;
// Convulve input as a function of odd/even row.
if((start + c)&1) {
ntsc_shift_ |= ((source & 4) >> 2) * 0x2222;
ntsc_shift_ |= ((source & 8) >> 3) * 0x1111;
ntsc_shift_ |= ((source & 1) >> 0) * 0x0888;
ntsc_shift_ |= ((source & 2) >> 1) * 0x0444;
uint32_t long_source;
if(c&1) {
long_source = uint32_t((source >> 2) | (source << 2) | (source << 6) | (source << 10));
} else {
ntsc_shift_ |= ((source & 1) >> 0) * 0x2222;
ntsc_shift_ |= ((source & 2) >> 1) * 0x1111;
ntsc_shift_ |= ((source & 4) >> 2) * 0x0888;
ntsc_shift_ |= ((source & 8) >> 3) * 0x0444;
long_source = uint32_t((source | (source << 4) | (source << 8) | (source << 12)) & 0x3fff);
}
// TODO: initial state?
target = output_shift(target, (c * 14) & 3);
ntsc_shift_ = (long_source << 18) | (ntsc_shift_ >> 14);
if(c) {
target = output_shift(target, 2 + (c * 14));
} else {
ntsc_shift_ |= ntsc_shift_ >> 14;
}
}
if(end == 40) {
ntsc_shift_ >>= 14;
target = output_shift(target, 2 + (40 * 14));
}
return target;