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Hardens the ZX80/81 video routines to ensure they never try to push data into the future and don't double-count time when pixels would ostensibly run into sync. You could previously see the CRT being handed negative run lengths if sync interrupted pixels or if a run of more than 320 pixels (my arbitrary buffer size) occurred, with corresponding poor behaviour given my use of unsigned numbers.

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This commit is contained in:
Thomas Harte 2017-07-09 19:33:05 -04:00
parent 8ccec37a4b
commit ed28260aaf
1 changed files with 11 additions and 9 deletions
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20
Machines/ZX8081/Video.cpp
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@ -50,9 +50,10 @@ void Video::flush(bool next_sync) {
// sync, or if we're past its end anyway. Otherwise let it be.
unsigned int data_length = (unsigned int)(line_data_pointer_ - line_data_);
if(data_length < cycles_since_update_ || next_sync) {
crt_->output_data(data_length, 1);
unsigned int output_length = std::min(data_length, cycles_since_update_);
crt_->output_data(output_length, 1);
line_data_pointer_ = line_data_ = nullptr;
cycles_since_update_ -= data_length;
cycles_since_update_ -= output_length;
} else return;
}
@ -86,19 +87,20 @@ void Video::output_byte(uint8_t byte) {
// If a buffer was obtained, serialise the new pixels.
if(line_data_) {
// If the buffer is full, output it now and obtain a new one
if(line_data_pointer_ - line_data_ == 320) {
crt_->output_data(320, 1);
cycles_since_update_ -= 320;
line_data_pointer_ = line_data_ = crt_->allocate_write_area(320);
if(!line_data_) return;
}
uint8_t mask = 0x80;
for(int c = 0; c < 8; c++) {
line_data_pointer_[c] = (byte & mask) ? 0xff : 0x00;
mask >>= 1;
}
line_data_pointer_ += 8;
// If that fills the buffer, output it now.
if(line_data_pointer_ - line_data_ == 320) {
crt_->output_data(320, 1);
line_data_pointer_ = line_data_ = nullptr;
cycles_since_update_ -= 160;
}
}
}