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Window accuracy improvements, implement a new CGB window glitch
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@LIJI32
LIJI32 committed Jul 21, 2024
1 parent 64cf389 commit d34579e
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Showing 4 changed files with 32 additions and 5 deletions.
25 changes: 24 additions & 1 deletion Core/display.c
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Original file line number Diff line number Diff line change
Expand Up @@ -791,6 +791,7 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
{
switch ((fetcher_step_t)gb->fetcher_state) {
case GB_FETCHER_GET_TILE_T1: {
gb->cgb_wx_glitch = GB_is_cgb(gb) && (uint8_t)(gb->position_in_line + 7 + gb->window_is_being_fetched) == gb->io_registers[GB_IO_WX];
uint16_t map = 0x1800;

if (!(gb->io_registers[GB_IO_LCDC] & GB_LCDC_WIN_ENABLE)) {
Expand Down Expand Up @@ -824,6 +825,10 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
gb->fetcher_state++;
break;
case GB_FETCHER_GET_TILE_T2: {
if (gb->cgb_wx_glitch) {
gb->fetcher_state++;
break;
}
dma_sync(gb, cycles);
gb->current_tile = vram_read(gb, gb->last_tile_index_address);
if (GB_is_cgb(gb)) {
Expand All @@ -836,6 +841,8 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
break;

case GB_FETCHER_GET_TILE_DATA_LOWER_T1: {
gb->cgb_wx_glitch = GB_is_cgb(gb) && (uint8_t)(gb->position_in_line + 7 + gb->window_is_being_fetched) == gb->io_registers[GB_IO_WX];

uint8_t y_flip = 0;
uint16_t tile_address = 0;
uint8_t y = gb->model > GB_MODEL_CGB_C ? gb->fetcher_y : fetcher_y(gb);
Expand All @@ -859,6 +866,11 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
break;

case GB_FETCHER_GET_TILE_DATA_LOWER_T2: {
if (gb->cgb_wx_glitch) {
gb->current_tile_data[0] = gb->current_tile_data[1];
gb->fetcher_state++;
break;
}
dma_sync(gb, cycles);
bool use_glitched = false;
bool cgb_d_glitch = false;
Expand All @@ -880,6 +892,8 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
break;

case GB_FETCHER_GET_TILE_DATA_HIGH_T1: {
gb->cgb_wx_glitch = GB_is_cgb(gb) && (uint8_t)(gb->position_in_line + 7 + gb->window_is_being_fetched) == gb->io_registers[GB_IO_WX];

uint16_t tile_address = 0;
uint8_t y = gb->model > GB_MODEL_CGB_C ? gb->fetcher_y : fetcher_y(gb);

Expand All @@ -903,6 +917,15 @@ static void advance_fetcher_state_machine(GB_gameboy_t *gb, unsigned *cycles)
break;

case GB_FETCHER_GET_TILE_DATA_HIGH_T2: {
if (gb->cgb_wx_glitch) {
gb->current_tile_data[1] = gb->current_tile_data[0];
gb->fetcher_state++;
if (gb->wx_triggered) {
gb->window_tile_x++;
gb->window_tile_x &= 0x1F;
}
break;
}
dma_sync(gb, cycles);
bool use_glitched = false;
bool cgb_d_glitch = false;
Expand Down Expand Up @@ -1707,7 +1730,7 @@ void GB_display_run(GB_gameboy_t *gb, unsigned cycles, bool force)
if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 7)) {
should_activate_window = true;
}
else if (gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed) {
else if (!GB_is_cgb(gb) && gb->io_registers[GB_IO_WX] == (uint8_t) (gb->position_in_line + 6) && !gb->wx_just_changed) {
should_activate_window = true;
/* LCD-PPU horizontal desync! It only appears to happen on DMGs, but not all of them.
This doesn't seem to be CPU revision dependent, but most revisions */
Expand Down
1 change: 1 addition & 0 deletions Core/gb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -648,6 +648,7 @@ struct GB_gameboy_internal_s {
uint8_t cpu_vram_bus;
uint32_t frame_parity_ticks;
bool last_tileset;
bool cgb_wx_glitch;
)

GB_SECTION(accessory,
Expand Down
1 change: 1 addition & 0 deletions Core/memory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1399,6 +1399,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
gb->wy_triggered = true;
}
case GB_IO_WX:
gb->cgb_wx_glitch = GB_is_cgb(gb) && (uint8_t)(gb->position_in_line + 7 + gb->window_is_being_fetched) == value;
case GB_IO_IF:
case GB_IO_SCX:
case GB_IO_SCY:
Expand Down
10 changes: 6 additions & 4 deletions Core/sm83_cpu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ typedef enum {
GB_CONFLICT_PALETTE_CGB,
GB_CONFLICT_DMG_LCDC,
GB_CONFLICT_SGB_LCDC,
GB_CONFLICT_WX,
GB_CONFLICT_WX_DMG,
GB_CONFLICT_LCDC_CGB,
GB_CONFLICT_LCDC_CGB_DOUBLE,
GB_CONFLICT_STAT_CGB_DOUBLE,
Expand All @@ -37,6 +37,7 @@ static const conflict_t cgb_conflict_map[0x80] = {
[GB_IO_OBP0] = GB_CONFLICT_PALETTE_CGB,
[GB_IO_OBP1] = GB_CONFLICT_PALETTE_CGB,
[GB_IO_SCX] = GB_CONFLICT_READ_OLD,
[GB_IO_WX] = GB_CONFLICT_WRITE_CPU,
};

static const conflict_t cgb_double_conflict_map[0x80] = {
Expand All @@ -46,6 +47,7 @@ static const conflict_t cgb_double_conflict_map[0x80] = {
[GB_IO_STAT] = GB_CONFLICT_STAT_CGB_DOUBLE,
[GB_IO_NR10] = GB_CONFLICT_NR10_CGB_DOUBLE,
[GB_IO_SCX] = GB_CONFLICT_SCX_CGB_DOUBLE,
[GB_IO_WX] = GB_CONFLICT_READ_OLD,
};

/* Todo: verify on an MGB */
Expand All @@ -60,7 +62,7 @@ static const conflict_t dmg_conflict_map[0x80] = {
[GB_IO_OBP0] = GB_CONFLICT_PALETTE_DMG,
[GB_IO_OBP1] = GB_CONFLICT_PALETTE_DMG,
[GB_IO_WY] = GB_CONFLICT_READ_OLD,
[GB_IO_WX] = GB_CONFLICT_WX,
[GB_IO_WX] = GB_CONFLICT_WX_DMG,

/* Todo: these were not verified at all */
[GB_IO_SCX] = GB_CONFLICT_READ_NEW,
Expand All @@ -78,7 +80,7 @@ static const conflict_t sgb_conflict_map[0x80] = {
[GB_IO_OBP0] = GB_CONFLICT_READ_NEW,
[GB_IO_OBP1] = GB_CONFLICT_READ_NEW,
[GB_IO_WY] = GB_CONFLICT_READ_OLD,
[GB_IO_WX] = GB_CONFLICT_WX,
[GB_IO_WX] = GB_CONFLICT_WX_DMG,

/* Todo: these were not verified at all */
[GB_IO_SCX] = GB_CONFLICT_READ_NEW,
Expand Down Expand Up @@ -258,7 +260,7 @@ static void cycle_write(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
break;
}

case GB_CONFLICT_WX:
case GB_CONFLICT_WX_DMG:
GB_advance_cycles(gb, gb->pending_cycles);
GB_write_memory(gb, addr, value);
gb->wx_just_changed = true;
Expand Down

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