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SameBoy/Core/display.c

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#include <stdbool.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include "gb.h"
/*
Each line is 456 cycles, approximately:
Mode 2 - 80 cycles / OAM Transfer
Mode 3 - 172 cycles / Rendering
Mode 0 - 204 cycles / HBlank
Mode 1 is VBlank
Todo: Mode lengths are not constants, see http://blog.kevtris.org/blogfiles/Nitty%20Gritty%20Gameboy%20VRAM%20Timing.txt
*/
#define MODE2_LENGTH (80)
#define MODE3_LENGTH (172)
#define MODE0_LENGTH (204)
#define LINE_LENGTH (MODE2_LENGTH + MODE3_LENGTH + MODE0_LENGTH) // = 456
#define LINES (144)
#define WIDTH (160)
#define VIRTUAL_LINES (LCDC_PERIOD / LINE_LENGTH) // = 154
typedef struct __attribute__((packed)) {
uint8_t y;
uint8_t x;
uint8_t tile;
uint8_t flags;
} GB_sprite_t;
static bool window_enabled(GB_gameboy_t *gb)
{
if ((gb->io_registers[GB_IO_LCDC] & 0x1) == 0) {
if (!gb->cgb_mode && gb->is_cgb) {
return false;
}
}
return (gb->io_registers[GB_IO_LCDC] & 0x20) && gb->io_registers[GB_IO_WX] < 167;
}
static uint32_t get_pixel(GB_gameboy_t *gb, uint8_t x, uint8_t y)
{
/*
Bit 7 - LCD Display Enable (0=Off, 1=On)
Bit 6 - Window Tile Map Display Select (0=9800-9BFF, 1=9C00-9FFF)
Bit 5 - Window Display Enable (0=Off, 1=On)
Bit 4 - BG & Window Tile Data Select (0=8800-97FF, 1=8000-8FFF)
Bit 3 - BG Tile Map Display Select (0=9800-9BFF, 1=9C00-9FFF)
Bit 2 - OBJ (Sprite) Size (0=8x8, 1=8x16)
Bit 1 - OBJ (Sprite) Display Enable (0=Off, 1=On)
Bit 0 - BG Display (for CGB see below) (0=Off, 1=On)
*/
uint16_t map = 0x1800;
uint8_t tile = 0;
uint8_t attributes = 0;
uint8_t sprite_palette = 0;
uint16_t tile_address = 0;
uint8_t background_pixel = 0, sprite_pixel = 0;
GB_sprite_t *sprite = (GB_sprite_t *) &gb->oam;
uint8_t sprites_in_line = 0;
bool lcd_8_16_mode = (gb->io_registers[GB_IO_LCDC] & 4) != 0;
bool sprites_enabled = (gb->io_registers[GB_IO_LCDC] & 2) != 0;
uint8_t lowest_sprite_x = 0xFF;
bool use_obp1 = false, priority = false;
bool in_window = false;
bool bg_enabled = true;
bool bg_behind = false;
if ((gb->io_registers[GB_IO_LCDC] & 0x1) == 0) {
if (gb->cgb_mode) {
bg_behind = true;
}
else {
bg_enabled = false;
}
}
if (window_enabled(gb) && y >= gb->io_registers[GB_IO_WY] + gb->wy_diff && x + 7 >= gb->io_registers[GB_IO_WX]) {
in_window = true;
}
if (sprites_enabled) {
// Loop all sprites
for (uint8_t i = 40; i--; sprite++) {
int sprite_y = sprite->y - 16;
int sprite_x = sprite->x - 8;
// Is sprite in our line?
if (sprite_y <= y && sprite_y + (lcd_8_16_mode? 16:8) > y) {
uint8_t tile_x, tile_y, current_sprite_pixel;
uint16_t line_address;
// Limit to 10 sprites in one scan line.
if (++sprites_in_line == 11) break;
// Does not overlap our pixel.
if (sprite_x > x || sprite_x + 8 <= x) continue;
tile_x = x - sprite_x;
tile_y = y - sprite_y;
if (sprite->flags & 0x20) tile_x = 7 - tile_x;
if (sprite->flags & 0x40) tile_y = (lcd_8_16_mode? 15:7) - tile_y;
line_address = (lcd_8_16_mode? sprite->tile & 0xFE : sprite->tile) * 0x10 + tile_y * 2;
if (gb->cgb_mode && (sprite->flags & 0x8)) {
line_address += 0x2000;
}
current_sprite_pixel = (((gb->vram[line_address ] >> ((~tile_x)&7)) & 1 ) |
((gb->vram[line_address + 1] >> ((~tile_x)&7)) & 1) << 1 );
/* From Pandocs:
When sprites with different x coordinate values overlap, the one with the smaller x coordinate
(closer to the left) will have priority and appear above any others. This applies in Non CGB Mode
only. When sprites with the same x coordinate values overlap, they have priority according to table
ordering. (i.e. $FE00 - highest, $FE04 - next highest, etc.) In CGB Mode priorities are always
assigned like this.
*/
if (current_sprite_pixel != 0) {
if (!gb->cgb_mode && sprite->x >= lowest_sprite_x) {
break;
}
sprite_pixel = current_sprite_pixel;
lowest_sprite_x = sprite->x;
use_obp1 = (sprite->flags & 0x10) != 0;
sprite_palette = sprite->flags & 7;
priority = (sprite->flags & 0x80) != 0;
if (gb->cgb_mode) {
break;
}
}
}
}
}
if (in_window) {
x -= gb->io_registers[GB_IO_WX] - 7; // Todo: This value is probably latched
y -= gb->io_registers[GB_IO_WY] + gb->wy_diff;
}
else {
x += gb->effective_scx;
y += gb->effective_scy;
}
if (gb->io_registers[GB_IO_LCDC] & 0x08 && !in_window) {
map = 0x1C00;
}
else if (gb->io_registers[GB_IO_LCDC] & 0x40 && in_window) {
map = 0x1C00;
}
tile = gb->vram[map + x/8 + y/8 * 32];
if (gb->cgb_mode) {
attributes = gb->vram[map + x/8 + y/8 * 32 + 0x2000];
}
if (attributes & 0x80) {
priority = !bg_behind && bg_enabled;
}
if (!priority && sprite_pixel) {
if (!gb->cgb_mode) {
sprite_pixel = (gb->io_registers[use_obp1? GB_IO_OBP1:GB_IO_OBP0] >> (sprite_pixel << 1)) & 3;
sprite_palette = use_obp1;
}
return gb->sprite_palettes_rgb[sprite_palette * 4 + sprite_pixel];
}
if (bg_enabled) {
if (gb->io_registers[GB_IO_LCDC] & 0x10) {
tile_address = tile * 0x10;
}
else {
tile_address = (int8_t) tile * 0x10 + 0x1000;
}
if (attributes & 0x8) {
tile_address += 0x2000;
}
if (attributes & 0x20) {
x = ~x;
}
if (attributes & 0x40) {
y = ~y;
}
background_pixel = (((gb->vram[tile_address + (y & 7) * 2 ] >> ((~x)&7)) & 1 ) |
((gb->vram[tile_address + (y & 7) * 2 + 1] >> ((~x)&7)) & 1) << 1 );
}
if (priority && sprite_pixel && !background_pixel) {
if (!gb->cgb_mode) {
sprite_pixel = (gb->io_registers[use_obp1? GB_IO_OBP1:GB_IO_OBP0] >> (sprite_pixel << 1)) & 3;
sprite_palette = use_obp1;
}
return gb->sprite_palettes_rgb[sprite_palette * 4 + sprite_pixel];
}
if (!gb->cgb_mode) {
background_pixel = ((gb->io_registers[GB_IO_BGP] >> (background_pixel << 1)) & 3);
}
return gb->background_palettes_rgb[(attributes & 7) * 4 + background_pixel];
}
static void display_vblank(GB_gameboy_t *gb)
{
if (gb->turbo) {
if (GB_timing_sync_turbo(gb)) {
return;
}
}
if (!gb->disable_rendering && ((!(gb->io_registers[GB_IO_LCDC] & 0x80) || gb->stopped) || gb->frame_skip_state == GB_FRAMESKIP_LCD_TURNED_ON)) {
/* LCD is off, set screen to white or black (if LCD is on in stop mode) */
uint32_t color = (gb->io_registers[GB_IO_LCDC] & 0x80) && gb->stopped ?
gb->rgb_encode_callback(gb, 0, 0, 0) :
gb->rgb_encode_callback(gb, 0xFF, 0xFF, 0xFF);
for (unsigned i = 0; i < WIDTH * LINES; i++) {
gb ->screen[i] = color;
}
}
gb->vblank_callback(gb);
GB_timing_sync(gb);
gb->vblank_just_occured = true;
}
static inline uint8_t scale_channel(uint8_t x)
{
return (x << 3) | (x >> 2);
}
static inline uint8_t scale_channel_with_curve(uint8_t x)
{
return (uint8_t[]){0,2,4,7,12,18,25,34,42,52,62,73,85,97,109,121,134,146,158,170,182,193,203,213,221,230,237,243,248,251,253,255,}[x];
}
uint32_t GB_convert_rgb15(GB_gameboy_t *gb, uint16_t color)
{
uint8_t r = (color) & 0x1F;
uint8_t g = (color >> 5) & 0x1F;
uint8_t b = (color >> 10) & 0x1F;
if (gb->color_correction_mode == GB_COLOR_CORRECTION_DISABLED) {
r = scale_channel(r);
g = scale_channel(g);
b = scale_channel(b);
}
else {
r = scale_channel_with_curve(r);
g = scale_channel_with_curve(g);
b = scale_channel_with_curve(b);
if (gb->color_correction_mode != GB_COLOR_CORRECTION_CORRECT_CURVES) {
uint8_t new_g = (g * 3 + b) / 4;
uint8_t new_r = r, new_b = b;
if (gb->color_correction_mode == GB_COLOR_CORRECTION_PRESERVE_BRIGHTNESS) {
uint8_t old_max = MAX(r, MAX(g, b));
uint8_t new_max = MAX(new_r, MAX(new_g, new_b));
if (new_max != 0) {
new_r = new_r * old_max / new_max;
new_g = new_g * old_max / new_max;
new_b = new_b * old_max / new_max;
}
uint8_t old_min = MIN(r, MIN(g, b));
uint8_t new_min = MIN(new_r, MIN(new_g, new_b));
if (new_min != 0xff) {
new_r = 0xff - (0xff - new_r) * (0xff - old_min) / (0xff - new_min);
new_g = 0xff - (0xff - new_g) * (0xff - old_min) / (0xff - new_min);
new_b = 0xff - (0xff - new_b) * (0xff - old_min) / (0xff - new_min);;
}
}
r = new_r;
g = new_g;
b = new_b;
}
}
return gb->rgb_encode_callback(gb, r, g, b);
}
void GB_palette_changed(GB_gameboy_t *gb, bool background_palette, uint8_t index)
{
if (!gb->rgb_encode_callback || !gb->is_cgb) return;
uint8_t *palette_data = background_palette? gb->background_palettes_data : gb->sprite_palettes_data;
uint16_t color = palette_data[index & ~1] | (palette_data[index | 1] << 8);
(background_palette? gb->background_palettes_rgb : gb->sprite_palettes_rgb)[index / 2] = GB_convert_rgb15(gb, color);
}
void GB_set_color_correction_mode(GB_gameboy_t *gb, GB_color_correction_mode_t mode)
{
gb->color_correction_mode = mode;
if (gb->is_cgb) {
for (unsigned i = 0; i < 32; i++) {
GB_palette_changed(gb, false, i * 2);
GB_palette_changed(gb, true, i * 2);
}
}
}
/*
STAT interrupt is implemented based on this finding:
http://board.byuu.org/phpbb3/viewtopic.php?p=25527#p25531
General timing is based on GiiBiiAdvance's documents:
https://github.com/AntonioND/giibiiadvance
*/
static void update_display_state(GB_gameboy_t *gb, uint8_t cycles)
{
if (!(gb->io_registers[GB_IO_LCDC] & 0x80)) {
/* LCD is disabled, state is constant */
/* When the LCD is off, LY is 0 and STAT mode is 0.
Todo: Verify the LY=LYC flag should be on. */
gb->io_registers[GB_IO_LY] = 0;
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 4;
gb->effective_scx = gb->io_registers[GB_IO_SCX];
if (gb->hdma_on_hblank) {
gb->hdma_on_hblank = false;
gb->hdma_on = false;
/* Todo: is this correct? */
gb->hdma_steps_left = 0xff;
}
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
/* Keep sending vblanks to user even if the screen is off */
gb->display_cycles += cycles;
if (gb->display_cycles >= LCDC_PERIOD) {
/* VBlank! */
gb->display_cycles -= LCDC_PERIOD;
display_vblank(gb);
}
/* Reset window rendering state */
gb->wy_diff = 0;
gb->window_disabled_while_active = false;
return;
}
uint8_t atomic_increase = gb->cgb_double_speed? 2 : 4;
/* According to AntonioND's docs this value should be 0 in CGB mode, but tests I ran on my CGB seem to contradict
these findings.
Todo: Investigate what causes the difference between our findings */
uint8_t stat_delay = gb->cgb_double_speed? 2 : 4; // (gb->cgb_mode? 0 : 4);
/* Todo: Is this correct for DMG mode CGB? */
uint8_t scx_delay = gb->effective_scx & 7;
if (gb->cgb_double_speed) {
scx_delay = (scx_delay + 1) & ~1;
}
else {
scx_delay = (scx_delay + (gb->first_scanline ? 2 : 0)) & ~3;
}
/* Todo: These are correct for DMG, DMG-mode CGB, and single speed CGB. Is is correct for double speed CGB? */
uint8_t oam_blocking_rush = gb->cgb_double_speed? 2 : 4;
uint8_t vram_blocking_rush = gb->is_cgb? 0 : 4;
for (; cycles; cycles -= atomic_increase) {
bool dmg_future_stat = false;
gb->io_registers[GB_IO_IF] |= gb->future_interrupts & 3;
gb->future_interrupts &= ~3;
bool previous_stat_interrupt_line = gb->stat_interrupt_line;
gb->stat_interrupt_line = false;
gb->display_cycles += atomic_increase;
/* The very first line is 4 clocks shorter when the LCD turns on. Verified on SGB2, CGB in CGB mode and
CGB in double speed mode. */
if (gb->first_scanline && gb->display_cycles >= LINE_LENGTH - 8) {
gb->first_scanline = false;
gb->display_cycles += 4;
}
bool should_compare_ly = true;
uint8_t ly_for_comparison = gb->io_registers[GB_IO_LY] = gb->display_cycles / LINE_LENGTH;
bool just_entered_hblank = false;
/* Handle cycle completion. STAT's initial value depends on model and mode */
if (gb->display_cycles == LCDC_PERIOD) {
/* VBlank! */
gb->display_cycles = 0;
gb->io_registers[GB_IO_STAT] &= ~3;
if (gb->is_cgb) {
if (stat_delay) {
gb->io_registers[GB_IO_STAT] |= 1;
}
else {
gb->io_registers[GB_IO_STAT] |= 2;
}
}
ly_for_comparison = gb->io_registers[GB_IO_LY] = 0;
/* Todo: verify timing */
gb->oam_read_blocked = true;
gb->vram_read_blocked = false;
gb->oam_write_blocked = true;
gb->vram_write_blocked = false;
/* Reset window rendering state */
gb->wy_diff = 0;
gb->window_disabled_while_active = false;
}
/* Entered VBlank state, update STAT and IF */
else if (gb->display_cycles == LINES * LINE_LENGTH + stat_delay) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 1;
if (gb->is_cgb) {
gb->future_interrupts |= 1;
}
else {
gb->io_registers[GB_IO_IF] |= 1;
}
/* Entering VBlank state triggers the OAM interrupt. In CGB, it happens 4 cycles earlier */
if (gb->io_registers[GB_IO_STAT] & 0x20 && !gb->is_cgb) {
gb->stat_interrupt_line = true;
}
if (gb->frame_skip_state == GB_FRAMESKIP_LCD_TURNED_ON) {
if (!gb->is_cgb) {
display_vblank(gb);
gb->frame_skip_state = GB_FRAMESKIP_SECOND_FRAME_RENDERED;
}
else {
gb->frame_skip_state = GB_FRAMESKIP_FIRST_FRAME_SKIPPED;
}
}
else {
gb->frame_skip_state = GB_FRAMESKIP_SECOND_FRAME_RENDERED;
display_vblank(gb);
}
}
/* Handle line 0 right after turning the LCD on */
else if (gb->first_scanline) {
/* OAM and VRAM blocking is not rushed in the very first scanline */
if (gb->display_cycles == atomic_increase) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
}
else if (gb->display_cycles == MODE2_LENGTH) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 3;
gb->effective_scx = gb->io_registers[GB_IO_SCX];
gb->oam_read_blocked = true;
gb->vram_read_blocked = true;
gb->oam_write_blocked = true;
gb->vram_write_blocked = true;
}
else if (gb->display_cycles == MODE2_LENGTH + MODE3_LENGTH + scx_delay) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
just_entered_hblank = true;
}
}
/* Handle STAT changes for lines 0-143 */
else if (gb->display_cycles < LINES * LINE_LENGTH) {
unsigned position_in_line = gb->display_cycles % LINE_LENGTH;
/* Handle OAM and VRAM blocking */
/* Todo: verify CGB timing for write blocking */
if (position_in_line == stat_delay - oam_blocking_rush ||
// In case stat_delay is 0
(position_in_line == LINE_LENGTH + stat_delay - oam_blocking_rush && gb->io_registers[GB_IO_LY] != 143)) {
gb->oam_read_blocked = true;
gb->oam_write_blocked = gb->is_cgb;
}
else if (position_in_line == MODE2_LENGTH + stat_delay - vram_blocking_rush) {
gb->vram_read_blocked = true;
gb->vram_write_blocked = gb->is_cgb;
}
if (position_in_line == stat_delay) {
gb->oam_write_blocked = true;
}
else if (!gb->is_cgb && position_in_line == MODE2_LENGTH + stat_delay - oam_blocking_rush) {
gb->oam_write_blocked = false;
}
else if (position_in_line == MODE2_LENGTH + stat_delay) {
gb->vram_write_blocked = true;
gb->oam_write_blocked = true;
}
/* Handle everything else */
/* OAM interrupt happens slightly before STAT is actually updated. (About 1-3 T-cycles)
Todo: Test double speed CGB */
if (position_in_line == 0 && stat_delay) {
if (gb->io_registers[GB_IO_STAT] & 0x20) {
gb->stat_interrupt_line = true;
dmg_future_stat = true;
}
}
if (position_in_line == stat_delay) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 2;
}
else if (position_in_line == 0 && gb->display_cycles != 0) {
should_compare_ly = gb->is_cgb;
ly_for_comparison--;
}
else if (position_in_line == MODE2_LENGTH + stat_delay) {
gb->io_registers[GB_IO_STAT] &= ~3;
gb->io_registers[GB_IO_STAT] |= 3;
gb->effective_scx = gb->io_registers[GB_IO_SCX];
gb->previous_lcdc_x = - (gb->effective_scx & 0x7);
}
else if (position_in_line == MODE2_LENGTH + MODE3_LENGTH + stat_delay + scx_delay) {
just_entered_hblank = true;
gb->io_registers[GB_IO_STAT] &= ~3;
gb->oam_read_blocked = false;
gb->vram_read_blocked = false;
gb->oam_write_blocked = false;
gb->vram_write_blocked = false;
if (gb->hdma_on_hblank) {
gb->hdma_on = true;
gb->hdma_cycles = 0;
}
}
}
/* Line 153 is special */
else if (gb->display_cycles >= (VIRTUAL_LINES - 1) * LINE_LENGTH) {
/* DMG */
if (!gb->is_cgb) {
switch (gb->display_cycles - (VIRTUAL_LINES - 1) * LINE_LENGTH) {
case 0:
should_compare_ly = false;
break;
case 4:
gb->io_registers[GB_IO_LY] = 0;
ly_for_comparison = VIRTUAL_LINES - 1;
break;
case 8:
gb->io_registers[GB_IO_LY] = 0;
should_compare_ly = false;
break;
default:
gb->io_registers[GB_IO_LY] = 0;
ly_for_comparison = 0;
}
}
/* CGB in DMG mode */
else if (!gb->cgb_mode) {
switch (gb->display_cycles - (VIRTUAL_LINES - 1) * LINE_LENGTH) {
case 0:
ly_for_comparison = VIRTUAL_LINES - 2;
break;
case 4:
break;
case 8:
gb->io_registers[GB_IO_LY] = 0;
break;
default:
gb->io_registers[GB_IO_LY] = 0;
ly_for_comparison = 0;
}
}
/* Single speed CGB */
else if (!gb->cgb_double_speed) {
switch (gb->display_cycles - (VIRTUAL_LINES - 1) * LINE_LENGTH) {
case 0:
break;
case 4:
gb->io_registers[GB_IO_LY] = 0;
break;
default:
gb->io_registers[GB_IO_LY] = 0;
ly_for_comparison = 0;
}
}
/* Double speed CGB */
else {
switch (gb->display_cycles - (VIRTUAL_LINES - 1) * LINE_LENGTH) {
case 0:
ly_for_comparison = VIRTUAL_LINES - 2;
break;
case 2:
case 4:
break;
case 6:
case 8:
gb->io_registers[GB_IO_LY] = 0;
break;
default:
gb->io_registers[GB_IO_LY] = 0;
ly_for_comparison = 0;
}
}
}
/* Lines 144 - 152 */
else {
if (stat_delay && gb->display_cycles % LINE_LENGTH == 0) {
should_compare_ly = gb->is_cgb;
ly_for_comparison--;
}
}
/* Set LY=LYC bit */
if (should_compare_ly && (ly_for_comparison == gb->io_registers[GB_IO_LYC])) {
gb->io_registers[GB_IO_STAT] |= 4;
}
else {
gb->io_registers[GB_IO_STAT] &= ~4;
}
if (!gb->stat_interrupt_line) {
switch (gb->io_registers[GB_IO_STAT] & 3) {
case 0:
gb->stat_interrupt_line = (gb->io_registers[GB_IO_STAT] & 8);
if (!gb->cgb_double_speed && just_entered_hblank && ((gb->effective_scx + (gb->first_scanline ? 2 : 0)) & 3) == 3) {
gb->stat_interrupt_line = false;
}
else if (just_entered_hblank && ((gb->effective_scx + (gb->first_scanline ? 2 : 0)) & 3) != 0) {
dmg_future_stat = true;
}
break;
case 1: gb->stat_interrupt_line = gb->io_registers[GB_IO_STAT] & 0x10; break;
case 2: gb->stat_interrupt_line = gb->io_registers[GB_IO_STAT] & 0x20; break;
}
/* User requested a LY=LYC interrupt and the LY=LYC bit is on */
if ((gb->io_registers[GB_IO_STAT] & 0x44) == 0x44) {
gb->stat_interrupt_line = true;
dmg_future_stat = false;
}
}
/* On the CGB, the last cycle of line 144 triggers an OAM interrupt
Todo: Verify timing for CGB in CGB mode and double speed CGB */
if (gb->is_cgb &&
gb->display_cycles == LINES * LINE_LENGTH + stat_delay - atomic_increase &&
(gb->io_registers[GB_IO_STAT] & 0x20)) {
gb->stat_interrupt_line = true;
}
if (gb->stat_interrupt_line && !previous_stat_interrupt_line) {
if (gb->is_cgb || dmg_future_stat) {
gb->future_interrupts |= 2;
}
else {
gb->io_registers[GB_IO_IF] |= 2;
}
}
};
#if 0
/* The value of LY is glitched in the last cycle of every line in CGB mode CGB in single speed
This is based on AntonioND's docs, however I could not reproduce these findings on my CGB.
Todo: Find out why my tests contradict these docs */
if (gb->cgb_mode && !gb->cgb_double_speed &&
gb->display_cycles % LINE_LENGTH == LINE_LENGTH - 4) {
uint8_t glitch_pattern[] = {0, 0, 2, 0, 4, 4, 6, 0, 8};
if ((gb->io_registers[GB_IO_LY] & 0xF) == 0xF) {
gb->io_registers[GB_IO_LY] = glitch_pattern[gb->io_registers[GB_IO_LY] >> 4] << 4;
}
else {
gb->io_registers[GB_IO_LY] = glitch_pattern[gb->io_registers[GB_IO_LY] & 7] | (gb->io_registers[GB_IO_LY] & 0xF8);
}
}
#endif
}
void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
{
update_display_state(gb, cycles);
if (gb->disable_rendering) {
return;
}
/*
Display controller bug: For some reason, the OAM STAT interrupt is called, as expected, for LY = 0..143.
However, it is also called from LY = 144.
See http://forums.nesdev.com/viewtopic.php?f=20&t=13727
*/
if (!(gb->io_registers[GB_IO_LCDC] & 0x80)) {
/* LCD is disabled, do nothing */
return;
}
if (gb->display_cycles >= LINE_LENGTH * 144) { /* VBlank */
return;
}
uint8_t effective_ly = gb->display_cycles / LINE_LENGTH;
if (gb->display_cycles % LINE_LENGTH < MODE2_LENGTH) { /* Mode 2 */
return;
}
/* Render */
int16_t current_lcdc_x = gb->display_cycles % LINE_LENGTH - MODE2_LENGTH - (gb->effective_scx & 0x7) - 7;
for (;gb->previous_lcdc_x < current_lcdc_x; gb->previous_lcdc_x++) {
if (gb->previous_lcdc_x >= WIDTH) {
continue;
}
if (((gb->previous_lcdc_x + gb->effective_scx) & 7) == 0) {
gb->effective_scy = gb->io_registers[GB_IO_SCY];
}
if (gb->previous_lcdc_x < 0) {
continue;
}
gb->screen[effective_ly * WIDTH + gb->previous_lcdc_x] =
get_pixel(gb, gb->previous_lcdc_x, effective_ly);
}
}
void GB_draw_tileset(GB_gameboy_t *gb, uint32_t *dest, GB_palette_type_t palette_type, uint8_t palette_index)
{
uint32_t none_palette[4];
uint32_t *palette = NULL;
switch (gb->is_cgb? palette_type : GB_PALETTE_NONE) {
default:
case GB_PALETTE_NONE:
none_palette[0] = gb->rgb_encode_callback(gb, 0xFF, 0xFF, 0xFF);
none_palette[1] = gb->rgb_encode_callback(gb, 0xAA, 0xAA, 0xAA);
none_palette[2] = gb->rgb_encode_callback(gb, 0x55, 0x55, 0x55);
none_palette[3] = gb->rgb_encode_callback(gb, 0, 0, 0 );
palette = none_palette;
break;
case GB_PALETTE_BACKGROUND:
palette = gb->background_palettes_rgb + (4 * (palette_index & 7));
break;
case GB_PALETTE_OAM:
palette = gb->sprite_palettes_rgb + (4 * (palette_index & 7));
break;
}
for (unsigned y = 0; y < 192; y++) {
for (unsigned x = 0; x < 256; x++) {
if (x >= 128 && !gb->is_cgb) {
*(dest++) = gb->background_palettes_rgb[0];
continue;
}
uint16_t tile = (x % 128) / 8 + y / 8 * 16;
uint16_t tile_address = tile * 0x10 + (x >= 128? 0x2000 : 0);
uint8_t pixel = (((gb->vram[tile_address + (y & 7) * 2 ] >> ((~x)&7)) & 1 ) |
((gb->vram[tile_address + (y & 7) * 2 + 1] >> ((~x)&7)) & 1) << 1);
if (!gb->cgb_mode) {
if (palette_type == GB_PALETTE_BACKGROUND) {
pixel = ((gb->io_registers[GB_IO_BGP] >> (pixel << 1)) & 3);
}
else if (!gb->cgb_mode) {
if (palette_type == GB_PALETTE_OAM) {
pixel = ((gb->io_registers[palette_index == 0? GB_IO_OBP0 : GB_IO_OBP1] >> (pixel << 1)) & 3);
}
}
}
*(dest++) = palette[pixel];
}
}
}
void GB_draw_tilemap(GB_gameboy_t *gb, uint32_t *dest, GB_palette_type_t palette_type, uint8_t palette_index, GB_map_type_t map_type, GB_tileset_type_t tileset_type)
{
uint32_t none_palette[4];
uint32_t *palette = NULL;
uint16_t map = 0x1800;
switch (gb->is_cgb? palette_type : GB_PALETTE_NONE) {
case GB_PALETTE_NONE:
none_palette[0] = gb->rgb_encode_callback(gb, 0xFF, 0xFF, 0xFF);
none_palette[1] = gb->rgb_encode_callback(gb, 0xAA, 0xAA, 0xAA);
none_palette[2] = gb->rgb_encode_callback(gb, 0x55, 0x55, 0x55);
none_palette[3] = gb->rgb_encode_callback(gb, 0, 0, 0 );
palette = none_palette;
break;
case GB_PALETTE_BACKGROUND:
palette = gb->background_palettes_rgb + (4 * (palette_index & 7));
break;
case GB_PALETTE_OAM:
palette = gb->sprite_palettes_rgb + (4 * (palette_index & 7));
break;
case GB_PALETTE_AUTO:
break;
}
if (map_type == GB_MAP_9C00 || (map_type == GB_MAP_AUTO && gb->io_registers[GB_IO_LCDC] & 0x08)) {
map = 0x1c00;
}
if (tileset_type == GB_TILESET_AUTO) {
tileset_type = (gb->io_registers[GB_IO_LCDC] & 0x10)? GB_TILESET_8800 : GB_TILESET_8000;
}
for (unsigned y = 0; y < 256; y++) {
for (unsigned x = 0; x < 256; x++) {
uint8_t tile = gb->vram[map + x/8 + y/8 * 32];
uint16_t tile_address;
uint8_t attributes = 0;
if (tileset_type == GB_TILESET_8800) {
tile_address = tile * 0x10;
}
else {
tile_address = (int8_t) tile * 0x10 + 0x1000;
}
if (gb->cgb_mode) {
attributes = gb->vram[map + x/8 + y/8 * 32 + 0x2000];
}
if (attributes & 0x8) {
tile_address += 0x2000;
}
uint8_t pixel = (((gb->vram[tile_address + (((attributes & 0x40)? ~y : y) & 7) * 2 ] >> (((attributes & 0x20)? x : ~x)&7)) & 1 ) |
((gb->vram[tile_address + (((attributes & 0x40)? ~y : y) & 7) * 2 + 1] >> (((attributes & 0x20)? x : ~x)&7)) & 1) << 1);
if (!gb->cgb_mode && (palette_type == GB_PALETTE_BACKGROUND || palette_type == GB_PALETTE_AUTO)) {
pixel = ((gb->io_registers[GB_IO_BGP] >> (pixel << 1)) & 3);
}
if (palette) {
*(dest++) = palette[pixel];
}
else {
*(dest++) = gb->background_palettes_rgb[(attributes & 7) * 4 + pixel];
}
}
}
}
uint8_t GB_get_oam_info(GB_gameboy_t *gb, GB_oam_info_t *dest, uint8_t *sprite_height)
{
uint8_t count = 0;
*sprite_height = (gb->io_registers[GB_IO_LCDC] & 4) ? 16:8;
uint8_t oam_to_dest_index[40] = {0,};
for (unsigned y = 0; y < LINES; y++) {
GB_sprite_t *sprite = (GB_sprite_t *) &gb->oam;
uint8_t sprites_in_line = 0;
for (uint8_t i = 0; i < 40; i++, sprite++) {
int sprite_y = sprite->y - 16;
bool obscured = false;
// Is sprite not in this line?
if (sprite_y > y || sprite_y + *sprite_height <= y) continue;
if (++sprites_in_line == 11) obscured = true;
GB_oam_info_t *info = NULL;
if (!oam_to_dest_index[i]) {
info = dest + count;
oam_to_dest_index[i] = ++count;
info->x = sprite->x;
info->y = sprite->y;
info->tile = *sprite_height == 16? sprite->tile & 0xFE : sprite->tile;
info->flags = sprite->flags;
info->obscured_by_line_limit = false;
info->oam_addr = 0xFE00 + i * sizeof(*sprite);
}
else {
info = dest + oam_to_dest_index[i] - 1;
}
info->obscured_by_line_limit |= obscured;
}
}
for (unsigned i = 0; i < count; i++) {
uint16_t vram_address = dest[i].tile * 0x10;
uint8_t flags = dest[i].flags;
uint8_t palette = gb->cgb_mode? (flags & 7) : ((flags & 0x10)? 1 : 0);
if (gb->is_cgb && (flags & 0x8)) {
vram_address += 0x2000;
}
for (unsigned y = 0; y < *sprite_height; y++) {
for (unsigned x = 0; x < 8; x++) {
uint8_t color = (((gb->vram[vram_address ] >> ((~x)&7)) & 1 ) |
((gb->vram[vram_address + 1] >> ((~x)&7)) & 1) << 1 );
if (!gb->cgb_mode) {
color = (gb->io_registers[palette? GB_IO_OBP1:GB_IO_OBP0] >> (color << 1)) & 3;
}
dest[i].image[((flags & 0x20)?7-x:x) + ((flags & 0x40)?*sprite_height - 1 -y:y) * 8] = gb->sprite_palettes_rgb[palette * 4 + color];
}
vram_address += 2;
}
}
return count;
}
/* Called when a write might enable or disable the window */
void GB_window_related_write(GB_gameboy_t *gb, uint8_t addr, uint8_t value)
{
bool before = window_enabled(gb);
gb->io_registers[addr] = value;
bool after = window_enabled(gb);
if (before != after && gb->display_cycles < LINES * LINE_LENGTH) {
/* Window was disabled or enabled outside of vblank */
uint8_t current_line = gb->display_cycles / LINE_LENGTH;
if (current_line >= gb->io_registers[GB_IO_WY]) {
if (after) {
if (!gb->window_disabled_while_active) {
/* Window was turned on for the first time this frame while LY > WY,
should start window in the next line */
gb->wy_diff = current_line + 1 - gb->io_registers[GB_IO_WY];
}
else {
gb->wy_diff += current_line;
}
}
else {
gb->wy_diff -= current_line;
gb->window_disabled_while_active = true;
}
}
}
}
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