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Hacky, but correct emulation of WX=166

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This commit is contained in:
Lior Halphon 2020-03-01 23:58:28 +02:00
parent 2a8b26d5e6
commit e846f4f3b0
2 changed files with 51 additions and 23 deletions
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72
Core/display.c
View File

@ -564,6 +564,7 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb)
if (!(gb->io_registers[GB_IO_LCDC] & 0x20)) {
gb->wx_triggered = false;
gb->wx166_glitch = false;
}
/* Todo: Verified for DMG (Tested: SGB2), CGB timing is wrong. */
@ -838,13 +839,13 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->vram_read_blocked = true;
gb->vram_write_blocked = true;
gb->wx_triggered = false;
gb->wx166_glitch = false;
goto mode_3_start;
while (true) {
/* Lines 0 - 143 */
gb->window_y = -1;
for (; gb->current_line < LINES; gb->current_line++) {
gb->wx_triggered = false;
/* Todo: verify timings */
if ((gb->io_registers[GB_IO_WY] == gb->current_line ||
(gb->current_line != 0 && gb->io_registers[GB_IO_WY] == gb->current_line - 1))) {
@ -945,29 +946,48 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
gb->fetcher_state = 0;
while (true) {
/* Handle window */
/* Todo: verify timings */
static const uint8_t scx_to_wx0_comparisons[] = {-7, -9, -10, -11, -12, -13, -14, -14};
/* TODO: It appears that WX checks if the window beings *next* pixel, not *this* pixel. For this reason,
WX=167 has no effect at all (It checks if the PPU X position is 161, which never happens) and WX=166
has weird artifacts (It appears to activate the window during HBlank, as PPU X is temporarily 160 at
that point. The code should be updated to represent this, and this will fix the time travel hack in
WX's access conflict code. */
if (!gb->wx_triggered && gb->wy_triggered && (gb->io_registers[GB_IO_LCDC] & 0x20)) {
if (gb->io_registers[GB_IO_WX] >= 167) {
// Too late to enable the window
}
else if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) ||
(gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed) ||
(gb->io_registers[GB_IO_WX] == 0 && (gb->position_in_line) == scx_to_wx0_comparisons[gb->io_registers[GB_IO_SCX] & 7])) {
gb->window_y++;
if (gb->io_registers[GB_IO_WX] != 166) {
/* TODO: Verify fetcher access timings in this case */
if (gb->io_registers[GB_IO_WX] == 0 && (gb->io_registers[GB_IO_SCX] & 7)) {
gb->cycles_for_line++;
GB_SLEEP(gb, display, 42, 1);
}
gb->wx_triggered = true;
gb->window_tile_x = 0;
fifo_clear(&gb->bg_fifo);
gb->fetcher_state = 0;
gb->window_is_being_fetched = true;
bool should_activate_window = false;
if (gb->io_registers[GB_IO_WX] == 0) {
static const uint8_t scx_to_wx0_comparisons[] = {-7, -9, -10, -11, -12, -13, -14, -14};
if (gb->position_in_line == scx_to_wx0_comparisons[gb->io_registers[GB_IO_SCX] & 7]) {
should_activate_window = true;
}
}
else if (gb->wx166_glitch) {
static const uint8_t scx_to_wx166_comparisons[] = {-8, -9, -10, -11, -12, -13, -14, -15};
if (gb->position_in_line == scx_to_wx166_comparisons[gb->io_registers[GB_IO_SCX] & 7]) {
should_activate_window = true;
}
}
else if (gb->io_registers[GB_IO_WX] < 166 + GB_is_cgb(gb)) {
if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7) ||
(gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed))
should_activate_window = true;
}
if (should_activate_window) {
gb->window_y++;
/* TODO: Verify fetcher access timings in this case */
if (gb->io_registers[GB_IO_WX] == 0 && (gb->io_registers[GB_IO_SCX] & 7)) {
gb->cycles_for_line++;
GB_SLEEP(gb, display, 42, 1);
}
gb->wx_triggered = true;
gb->window_tile_x = 0;
fifo_clear(&gb->bg_fifo);
gb->fetcher_state = 0;
gb->window_is_being_fetched = true;
}
else if (!GB_is_cgb(gb) && gb->io_registers[GB_IO_WX] == 166 && gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7)) {
gb->window_y++;
}
}
/* TODO: What happens when WX=0? */
@ -1075,6 +1095,14 @@ abort_fetching_object:
gb->cycles_for_line++;
GB_SLEEP(gb, display, 21, 1);
}
/* TODO: Verify timing */
if (!GB_is_cgb(gb) && gb->wy_triggered && (gb->io_registers[GB_IO_LCDC] & 0x20) && gb->io_registers[GB_IO_WX] == 166) {
gb->wx166_glitch = true;
}
else {
gb->wx166_glitch = false;
}
gb->wx_triggered = false;
if (GB_is_cgb(gb) && gb->model <= GB_MODEL_CGB_C) {
gb->cycles_for_line++;
@ -1129,7 +1157,7 @@ abort_fetching_object:
gb->icd_hreset_callback(gb);
}
}
gb->wx166_glitch = false;
/* Lines 144 - 152 */
for (; gb->current_line < VIRTUAL_LINES - 1; gb->current_line++) {
gb->io_registers[GB_IO_LY] = gb->current_line;

2
Core/gb.h
View File

@ -501,7 +501,7 @@ struct GB_gameboy_internal_s {
uint8_t current_tile_data[2];
uint8_t fetcher_state;
bool window_is_being_fetched;
GB_PADDING(bool,oam_fifo_paused);
bool wx166_glitch;
bool wx_triggered;
uint8_t visible_objs[10];
uint8_t obj_comparators[10];