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Emulate changing sprite height mid-fetch

This commit is contained in:
Lior Halphon 2020-02-21 16:43:51 +02:00
parent 7d51ba3d97
commit 8409d3bcfb
3 changed files with 42 additions and 22 deletions
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61
Core/display.c
View File

@ -680,6 +680,30 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb)
gb->fetcher_state &= 7;
}
static uint16_t get_object_line_address(GB_gameboy_t *gb, const GB_object_t *object)
{
/* TODO: what does the PPU read if DMA is active? */
if (gb->oam_ppu_blocked) {
static const GB_object_t blocked = {0xFF, 0xFF, 0xFF, 0xFF};
object = &blocked;
}
bool height_16 = (gb->io_registers[GB_IO_LCDC] & 4) != 0; /* Todo: Which T-cycle actually reads this? */
uint8_t tile_y = (gb->current_line - object->y) & (height_16? 0xF : 7);
if (object->flags & 0x40) { /* Flip Y */
tile_y ^= height_16? 0xF : 7;
}
/* Todo: I'm not 100% sure an access to OAM can't trigger the OAM bug while we're accessing this */
uint16_t line_address = (height_16? object->tile & 0xFE : object->tile) * 0x10 + tile_y * 2;
if (gb->cgb_mode && (object->flags & 0x8)) { /* Use VRAM bank 2 */
line_address += 0x2000;
}
return line_address;
}
/*
TODO: It seems that the STAT register's mode bits are always "late" by 4 T-cycles.
The PPU logic can be greatly simplified if that delay is simply emulated.
@ -736,6 +760,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
GB_STATE(gb, display, 37);
GB_STATE(gb, display, 38);
GB_STATE(gb, display, 39);
GB_STATE(gb, display, 40);
}
@ -931,42 +956,34 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
}
}
gb->cycles_for_line += 5;
GB_SLEEP(gb, display, 20, 5);
gb->cycles_for_line += 4;
GB_SLEEP(gb, display, 20, 4);
if (gb->object_fetch_aborted) {
goto abort_fetching_object;
}
gb->during_object_fetch = false;
gb->object_low_line_address = get_object_line_address(gb, &objects[gb->visible_objs[gb->n_visible_objs - 1]]);
gb->cycles_for_line++;
GB_SLEEP(gb, display, 39, 1);
if (gb->object_fetch_aborted) {
goto abort_fetching_object;
}
gb->during_object_fetch = false;
gb->cycles_for_line++;
GB_SLEEP(gb, display, 40, 1);
/* TODO: what does the PPU read if DMA is active? */
const GB_object_t *object = &objects[gb->visible_objs[gb->n_visible_objs - 1]];
if (gb->oam_ppu_blocked) {
static const GB_object_t blocked = {0xFF, 0xFF, 0xFF, 0xFF};
object = &blocked;
}
bool height_16 = (gb->io_registers[GB_IO_LCDC] & 4) != 0; /* Todo: Which T-cycle actually reads this? */
uint8_t tile_y = (gb->current_line - object->y) & (height_16? 0xF : 7);
if (object->flags & 0x40) { /* Flip Y */
tile_y ^= height_16? 0xF : 7;
}
/* Todo: I'm not 100% sure an access to OAM can't trigger the OAM bug while we're accessing this */
uint16_t line_address = (height_16? object->tile & 0xFE : object->tile) * 0x10 + tile_y * 2;
if (gb->cgb_mode && (object->flags & 0x8)) { /* Use VRAM bank 2 */
line_address += 0x2000;
}
uint16_t line_address = get_object_line_address(gb, object);
uint8_t palette = (object->flags & 0x10) ? 1 : 0;
if (gb->cgb_mode) {
palette = object->flags & 0x7;
}
fifo_overlay_object_row(&gb->oam_fifo,
gb->vram_ppu_blocked? 0xFF : gb->vram[line_address],
gb->vram_ppu_blocked? 0xFF : gb->vram[gb->object_low_line_address],
gb->vram_ppu_blocked? 0xFF : gb->vram[line_address + 1],
palette,
object->flags & 0x80,

1
Core/gb.h
View File

@ -520,6 +520,7 @@ struct GB_gameboy_internal_s {
bool cgb_palettes_ppu_blocked;
bool object_fetch_aborted;
bool during_object_fetch;
uint16_t object_low_line_address;
);
/* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */

2
Core/save_state.c
View File

@ -265,6 +265,7 @@ int GB_load_state(GB_gameboy_t *gb, const char *path)
gb->bg_fifo.write_end &= 0xF;
gb->oam_fifo.read_end &= 0xF;
gb->oam_fifo.write_end &= 0xF;
gb->object_low_line_address &= gb->vram_size & ~1;
if (gb->object_priority == GB_OBJECT_PRIORITY_UNDEFINED) {
gb->object_priority = gb->cgb_mode? GB_OBJECT_PRIORITY_INDEX : GB_OBJECT_PRIORITY_X;
@ -374,6 +375,7 @@ int GB_load_state_from_buffer(GB_gameboy_t *gb, const uint8_t *buffer, size_t le
gb->bg_fifo.write_end &= 0xF;
gb->oam_fifo.read_end &= 0xF;
gb->oam_fifo.write_end &= 0xF;
gb->object_low_line_address &= gb->vram_size & ~1;
if (gb->object_priority == GB_OBJECT_PRIORITY_UNDEFINED) {
gb->object_priority = gb->cgb_mode? GB_OBJECT_PRIORITY_INDEX : GB_OBJECT_PRIORITY_X;