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Emulate window pixel insertion glitch, fixes Star Trek - 25th Anniversary, closes #278

This commit is contained in:
Lior Halphon 2022-07-22 00:27:21 +03:00
parent 3a86b868fe
commit 1fedb81ab7
1 changed files with 29 additions and 4 deletions
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33
Core/display.c
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@ -1294,8 +1294,17 @@ static inline uint16_t mode3_batching_length(GB_gameboy_t *gb)
if (gb->hdma_on) return 0;
if (gb->stopped) return 0;
if (GB_is_dma_active(gb)) return 0;
if (gb->wy_triggered && (gb->io_registers[GB_IO_LCDC] & 0x20) && (gb->io_registers[GB_IO_WX] < 8 || gb->io_registers[GB_IO_WX] == 166)) {
return 0;
if (gb->wy_triggered) {
if (gb->io_registers[GB_IO_LCDC] & 0x20) {
if ((gb->io_registers[GB_IO_WX] < 8 || gb->io_registers[GB_IO_WX] == 166)) {
return 0;
}
}
else {
if (gb->io_registers[GB_IO_WX] < 167 && !GB_is_cgb(gb)) {
return 0;
}
}
}
// No objects or window, timing is trivial
@ -1683,15 +1692,31 @@ void GB_display_run(GB_gameboy_t *gb, unsigned cycles, bool force)
}
}
/* TODO: What happens when WX=0? */
/* TODO: What happens when WX=0? When the fifo is full? */
if (!GB_is_cgb(gb) && gb->wx_triggered && !gb->window_is_being_fetched &&
gb->fetcher_state == 0 && gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) ) {
gb->fetcher_state == 0 && gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) && gb->bg_fifo.size == 8) {
// Insert a pixel right at the FIFO's end
gb->bg_fifo.read_end--;
gb->bg_fifo.read_end &= GB_FIFO_LENGTH - 1;
gb->bg_fifo.fifo[gb->bg_fifo.read_end] = (GB_fifo_item_t){0,};
gb->bg_fifo.size++;
gb->window_is_being_fetched = false;
}
/* TODO: WX=0 behaves wrong, but WX=0 behaves wrong regardless in DMG mode */
if (!GB_is_cgb(gb) && gb->wy_triggered && !(gb->io_registers[GB_IO_LCDC] & 0x20) && gb->bg_fifo.size == 1) {
/* See https://github.com/LIJI32/SameBoy/issues/278 for documentation */
uint8_t logical_position = gb->position_in_line + 8;
if (logical_position >= (uint8_t)(-8)) {
logical_position += 8;
}
if (gb->io_registers[GB_IO_WX] == logical_position) {
gb->bg_fifo.read_end--;
gb->bg_fifo.read_end &= GB_FIFO_LENGTH - 1;
gb->bg_fifo.fifo[gb->bg_fifo.read_end] = (GB_fifo_item_t){0,};
gb->bg_fifo.size = 2;
}
}
/* Handle objects */
/* When the object enabled bit is off, this proccess is skipped entirely on the DMG, but not on the CGB.